text: /*-------------------------------------------------------------------------
   *
   * parse_coerce.c
   *		handle type coercions/conversions for parser
   *
   * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/parser/parse_coerce.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "catalog/pg_cast.h"
  #include "catalog/pg_class.h"
  #include "catalog/pg_inherits.h"
  #include "catalog/pg_proc.h"
  #include "catalog/pg_type.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "parser/parse_coerce.h"
  #include "parser/parse_relation.h"
  #include "parser/parse_type.h"
  #include "utils/builtins.h"
  #include "utils/datum.h"		/* needed for datumIsEqual() */
  #include "utils/fmgroids.h"
  #include "utils/lsyscache.h"
  #include "utils/syscache.h"
  #include "utils/typcache.h"
  
  
  static Node *coerce_type_typmod(Node *node,
  								Oid targetTypeId, int32 targetTypMod,
  								CoercionContext ccontext, CoercionForm cformat,
  								int location,
  								bool hideInputCoercion);
  static void hide_coercion_node(Node *node);
  static Node *build_coercion_expression(Node *node,
  									   CoercionPathType pathtype,
  									   Oid funcId,
  									   Oid targetTypeId, int32 targetTypMod,
  									   CoercionContext ccontext, CoercionForm cformat,
  									   int location);
  static Node *coerce_record_to_complex(ParseState *pstate, Node *node,
  									  Oid targetTypeId,
  									  CoercionContext ccontext,
  									  CoercionForm cformat,
  									  int location);
  static bool is_complex_array(Oid typid);
  static bool typeIsOfTypedTable(Oid reltypeId, Oid reloftypeId);
  
  
  /*
   * coerce_to_target_type()
   *		Convert an expression to a target type and typmod.
   *
   * This is the general-purpose entry point for arbitrary type coercion
   * operations.  Direct use of the component operations can_coerce_type,
   * coerce_type, and coerce_type_typmod should be restricted to special
   * cases (eg, when the conversion is expected to succeed).
   *
   * Returns the possibly-transformed expression tree, or NULL if the type
   * conversion is not possible.  (We do this, rather than ereport'ing directly,
   * so that callers can generate custom error messages indicating context.)
   *
   * pstate - parse state (can be NULL, see coerce_type)
   * expr - input expression tree (already transformed by transformExpr)
   * exprtype - result type of expr
   * targettype - desired result type
   * targettypmod - desired result typmod
   * ccontext, cformat - context indicators to control coercions
   * location - parse location of the coercion request, or -1 if unknown/implicit
   */
  Node *
  coerce_to_target_type(ParseState *pstate, Node *expr, Oid exprtype,
  					  Oid targettype, int32 targettypmod,
  					  CoercionContext ccontext,
  					  CoercionForm cformat,
  					  int location)
  {
  	Node	   *result;
  	Node	   *origexpr;
  
  	if (!can_coerce_type(1, &exprtype, &targettype, ccontext))
  		return NULL;
  
  	/*
  	 * If the input has a CollateExpr at the top, strip it off, perform the
  	 * coercion, and put a new one back on.  This is annoying since it
  	 * duplicates logic in coerce_type, but if we don't do this then it's too
  	 * hard to tell whether coerce_type actually changed anything, and we
  	 * *must* know that to avoid possibly calling hide_coercion_node on
  	 * something that wasn't generated by coerce_type.  Note that if there are
  	 * multiple stacked CollateExprs, we just discard all but the topmost.
  	 * Also, if the target type isn't collatable, we discard the CollateExpr.
  	 */
  	origexpr = expr;
  	while (expr && IsA(expr, CollateExpr))
  		expr = (Node *) ((CollateExpr *) expr)->arg;
  
  	result = coerce_type(pstate, expr, exprtype,
  						 targettype, targettypmod,
  						 ccontext, cformat, location);
  
  	/*
  	 * If the target is a fixed-length type, it may need a length coercion as
  	 * well as a type coercion.  If we find ourselves adding both, force the
  	 * inner coercion node to implicit display form.
  	 */
  	result = coerce_type_typmod(result,
  								targettype, targettypmod,
  								ccontext, cformat, location,
  								(result != expr && !IsA(result, Const)));
  
  	if (expr != origexpr && type_is_collatable(targettype))
  	{
  		/* Reinstall top CollateExpr */
  		CollateExpr *coll = (CollateExpr *) origexpr;
  		CollateExpr *newcoll = makeNode(CollateExpr);
  
  		newcoll->arg = (Expr *) result;
  		newcoll->collOid = coll->collOid;
  		newcoll->location = coll->location;
  		result = (Node *) newcoll;
  	}
  
  	return result;
  }
  
  
  /*
   * coerce_type()
   *		Convert an expression to a different type.
   *
   * The caller should already have determined that the coercion is possible;
   * see can_coerce_type.
   *
   * Normally, no coercion to a typmod (length) is performed here.  The caller
   * must call coerce_type_typmod as well, if a typmod constraint is wanted.
   * (But if the target type is a domain, it may internally contain a
   * typmod constraint, which will be applied inside coerce_to_domain.)
   * In some cases pg_cast specifies a type coercion function that also
   * applies length conversion, and in those cases only, the result will
   * already be properly coerced to the specified typmod.
   *
   * pstate is only used in the case that we are able to resolve the type of
   * a previously UNKNOWN Param.  It is okay to pass pstate = NULL if the
   * caller does not want type information updated for Params.
   *
   * Note: this function must not modify the given expression tree, only add
   * decoration on top of it.  See transformSetOperationTree, for example.
   */
  Node *
  coerce_type(ParseState *pstate, Node *node,
  			Oid inputTypeId, Oid targetTypeId, int32 targetTypeMod,
  			CoercionContext ccontext, CoercionForm cformat, int location)
  {
  	Node	   *result;
  	CoercionPathType pathtype;
  	Oid			funcId;
  
  	if (targetTypeId == inputTypeId ||
  		node == NULL)
  	{
  		/* no conversion needed */
  		return node;
  	}
  	if (targetTypeId == ANYOID ||
  		targetTypeId == ANYELEMENTOID ||
  		targetTypeId == ANYNONARRAYOID ||
  		targetTypeId == ANYCOMPATIBLEOID ||
  		targetTypeId == ANYCOMPATIBLENONARRAYOID)
  	{
  		/*
  		 * Assume can_coerce_type verified that implicit coercion is okay.
  		 *
  		 * Note: by returning the unmodified node here, we are saying that
  		 * it's OK to treat an UNKNOWN constant as a valid input for a
  		 * function accepting one of these pseudotypes.  This should be all
  		 * right, since an UNKNOWN value is still a perfectly valid Datum.
  		 *
  		 * NB: we do NOT want a RelabelType here: the exposed type of the
  		 * function argument must be its actual type, not the polymorphic
  		 * pseudotype.
  		 */
  		return node;
  	}
  	if (targetTypeId == ANYARRAYOID ||
  		targetTypeId == ANYENUMOID ||
  		targetTypeId == ANYRANGEOID ||
  		targetTypeId == ANYMULTIRANGEOID ||
  		targetTypeId == ANYCOMPATIBLEARRAYOID ||
  		targetTypeId == ANYCOMPATIBLERANGEOID ||
  		targetTypeId == ANYCOMPATIBLEMULTIRANGEOID)
  	{
  		/*
  		 * Assume can_coerce_type verified that implicit coercion is okay.
  		 *
  		 * These cases are unlike the ones above because the exposed type of
  		 * the argument must be an actual array, enum, range, or multirange
  		 * type.  In particular the argument must *not* be an UNKNOWN
  		 * constant.  If it is, we just fall through; below, we'll call the
  		 * pseudotype's input function, which will produce an error.  Also, if
  		 * what we have is a domain over array, enum, range, or multirange, we
  		 * have to relabel it to its base type.
  		 *
  		 * Note: currently, we can't actually see a domain-over-enum here,
  		 * since the other functions in this file will not match such a
  		 * parameter to ANYENUM.  But that should get changed eventually.
  		 */
  		if (inputTypeId != UNKNOWNOID)
  		{
  			Oid			baseTypeId = getBaseType(inputTypeId);
  
  			if (baseTypeId != inputTypeId)
  			{
  				RelabelType *r = makeRelabelType((Expr *) node,
  												 baseTypeId, -1,
  												 InvalidOid,
  												 cformat);
  
  				r->location = location;
  				return (Node *) r;
  			}
  			/* Not a domain type, so return it as-is */
  			return node;
  		}
  	}
  	if (inputTypeId == UNKNOWNOID && IsA(node, Const))
  	{
  		/*
  		 * Input is a string constant with previously undetermined type. Apply
  		 * the target type's typinput function to it to produce a constant of
  		 * the target type.
  		 *
  		 * NOTE: this case cannot be folded together with the other
  		 * constant-input case, since the typinput function does not
  		 * necessarily behave the same as a type conversion function. For
  		 * example, int4's typinput function will reject "1.2", whereas
  		 * float-to-int type conversion will round to integer.
  		 *
  		 * XXX if the typinput function is not immutable, we really ought to
  		 * postpone evaluation of the function call until runtime. But there
  		 * is no way to represent a typinput function call as an expression
  		 * tree, because C-string values are not Datums. (XXX This *is*
  		 * possible as of 7.3, do we want to do it?)
  		 */
  		Const	   *con = (Const *) node;
  		Const	   *newcon = makeNode(Const);
  		Oid			baseTypeId;
  		int32		baseTypeMod;
  		int32		inputTypeMod;
  		Type		baseType;
  		ParseCallbackState pcbstate;
  
  		/*
  		 * If the target type is a domain, we want to call its base type's
  		 * input routine, not domain_in().  This is to avoid premature failure
  		 * when the domain applies a typmod: existing input routines follow
  		 * implicit-coercion semantics for length checks, which is not always
  		 * what we want here.  The needed check will be applied properly
  		 * inside coerce_to_domain().
  		 */
  		baseTypeMod = targetTypeMod;
  		baseTypeId = getBaseTypeAndTypmod(targetTypeId, &baseTypeMod);
  
  		/*
  		 * For most types we pass typmod -1 to the input routine, because
  		 * existing input routines follow implicit-coercion semantics for
  		 * length checks, which is not always what we want here.  Any length
  		 * constraint will be applied later by our caller.  An exception
  		 * however is the INTERVAL type, for which we *must* pass the typmod
  		 * or it won't be able to obey the bizarre SQL-spec input rules. (Ugly
  		 * as sin, but so is this part of the spec...)
  		 */
  		if (baseTypeId == INTERVALOID)
  			inputTypeMod = baseTypeMod;
  		else
  			inputTypeMod = -1;
  
  		baseType = typeidType(baseTypeId);
  
  		newcon->consttype = baseTypeId;
  		newcon->consttypmod = inputTypeMod;
  		newcon->constcollid = typeTypeCollation(baseType);
  		newcon->constlen = typeLen(baseType);
  		newcon->constbyval = typeByVal(baseType);
  		newcon->constisnull = con->constisnull;
  
  		/*
  		 * We use the original literal's location regardless of the position
  		 * of the coercion.  This is a change from pre-9.2 behavior, meant to
  		 * simplify life for pg_stat_statements.
  		 */
  		newcon->location = con->location;
  
  		/*
  		 * Set up to point at the constant's text if the input routine throws
  		 * an error.
  		 */
  		setup_parser_errposition_callback(&pcbstate, pstate, con->location);
  
  		/*
  		 * We assume here that UNKNOWN's internal representation is the same
  		 * as CSTRING.
  		 */
  		if (!con->constisnull)
  			newcon->constvalue = stringTypeDatum(baseType,
  												 DatumGetCString(con->constvalue),
  												 inputTypeMod);
  		else
  			newcon->constvalue = stringTypeDatum(baseType,
  												 NULL,
  												 inputTypeMod);
  
  		/*
  		 * If it's a varlena value, force it to be in non-expanded
  		 * (non-toasted) format; this avoids any possible dependency on
  		 * external values and improves consistency of representation.
  		 */
  		if (!con->constisnull && newcon->constlen == -1)
  			newcon->constvalue =
  				PointerGetDatum(PG_DETOAST_DATUM(newcon->constvalue));
  
  #ifdef RANDOMIZE_ALLOCATED_MEMORY
  
  		/*
  		 * For pass-by-reference data types, repeat the conversion to see if
  		 * the input function leaves any uninitialized bytes in the result. We
  		 * can only detect that reliably if RANDOMIZE_ALLOCATED_MEMORY is
  		 * enabled, so we don't bother testing otherwise.  The reason we don't
  		 * want any instability in the input function is that comparison of
  		 * Const nodes relies on bytewise comparison of the datums, so if the
  		 * input function leaves garbage then subexpressions that should be
  		 * identical may not get recognized as such.  See pgsql-hackers
  		 * discussion of 2008-04-04.
  		 */
  		if (!con->constisnull && !newcon->constbyval)
  		{
  			Datum		val2;
  
  			val2 = stringTypeDatum(baseType,
  								   DatumGetCString(con->constvalue),
  								   inputTypeMod);
  			if (newcon->constlen == -1)
  				val2 = PointerGetDatum(PG_DETOAST_DATUM(val2));
  			if (!datumIsEqual(newcon->constvalue, val2, false, newcon->constlen))
  				elog(WARNING, "type %s has unstable input conversion for \"%s\"",
  					 typeTypeName(baseType), DatumGetCString(con->constvalue));
  		}
  #endif
  
  		cancel_parser_errposition_callback(&pcbstate);
  
  		result = (Node *) newcon;
  
  		/* If target is a domain, apply constraints. */
  		if (baseTypeId != targetTypeId)
  			result = coerce_to_domain(result,
  									  baseTypeId, baseTypeMod,
  									  targetTypeId,
  									  ccontext, cformat, location,
  									  false);
  
  		ReleaseSysCache(baseType);
  
  		return result;
  	}
  	if (IsA(node, Param) &&
  		pstate != NULL && pstate->p_coerce_param_hook != NULL)
  	{
  		/*
  		 * Allow the CoerceParamHook to decide what happens.  It can return a
  		 * transformed node (very possibly the same Param node), or return
  		 * NULL to indicate we should proceed with normal coercion.
  		 */
  		result = pstate->p_coerce_param_hook(pstate,
  											 (Param *) node,
  											 targetTypeId,
  											 targetTypeMod,
  											 location);
  		if (result)
  			return result;
  	}
  	if (IsA(node, CollateExpr))
  	{
  		/*
  		 * If we have a COLLATE clause, we have to push the coercion
  		 * underneath the COLLATE; or discard the COLLATE if the target type
  		 * isn't collatable.  This is really ugly, but there is little choice
  		 * because the above hacks on Consts and Params wouldn't happen
  		 * otherwise.  This kluge has consequences in coerce_to_target_type.
  		 */
  		CollateExpr *coll = (CollateExpr *) node;
  
  		result = coerce_type(pstate, (Node *) coll->arg,
  							 inputTypeId, targetTypeId, targetTypeMod,
  							 ccontext, cformat, location);
  		if (type_is_collatable(targetTypeId))
  		{
  			CollateExpr *newcoll = makeNode(CollateExpr);
  
  			newcoll->arg = (Expr *) result;
  			newcoll->collOid = coll->collOid;
  			newcoll->location = coll->location;
  			result = (Node *) newcoll;
  		}
  		return result;
  	}
  	pathtype = find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
  									 &funcId);
  	if (pathtype != COERCION_PATH_NONE)
  	{
  		if (pathtype != COERCION_PATH_RELABELTYPE)
  		{
  			/*
  			 * Generate an expression tree representing run-time application
  			 * of the conversion function.  If we are dealing with a domain
  			 * target type, the conversion function will yield the base type,
  			 * and we need to extract the correct typmod to use from the
  			 * domain's typtypmod.
  			 */
  			Oid			baseTypeId;
  			int32		baseTypeMod;
  
  			baseTypeMod = targetTypeMod;
  			baseTypeId = getBaseTypeAndTypmod(targetTypeId, &baseTypeMod);
  
  			result = build_coercion_expression(node, pathtype, funcId,
  											   baseTypeId, baseTypeMod,
  											   ccontext, cformat, location);
  
  			/*
  			 * If domain, coerce to the domain type and relabel with domain
  			 * type ID, hiding the previous coercion node.
  			 */
  			if (targetTypeId != baseTypeId)
  				result = coerce_to_domain(result, baseTypeId, baseTypeMod,
  										  targetTypeId,
  										  ccontext, cformat, location,
  										  true);
  		}
  		else
  		{
  			/*
  			 * We don't need to do a physical conversion, but we do need to
  			 * attach a RelabelType node so that the expression will be seen
  			 * to have the intended type when inspected by higher-level code.
  			 *
  			 * Also, domains may have value restrictions beyond the base type
  			 * that must be accounted for.  If the destination is a domain
  			 * then we won't need a RelabelType node.
  			 */
  			result = coerce_to_domain(node, InvalidOid, -1, targetTypeId,
  									  ccontext, cformat, location,
  									  false);
  			if (result == node)
  			{
  				/*
  				 * XXX could we label result with exprTypmod(node) instead of
  				 * default -1 typmod, to save a possible length-coercion
  				 * later? Would work if both types have same interpretation of
  				 * typmod, which is likely but not certain.
  				 */
  				RelabelType *r = makeRelabelType((Expr *) result,
  												 targetTypeId, -1,
  												 InvalidOid,
  												 cformat);
  
  				r->location = location;
  				result = (Node *) r;
  			}
  		}
  		return result;
  	}
  	if (inputTypeId == RECORDOID &&
  		ISCOMPLEX(targetTypeId))
  	{
  		/* Coerce a RECORD to a specific complex type */
  		return coerce_record_to_complex(pstate, node, targetTypeId,
  										ccontext, cformat, location);
  	}
  	if (targetTypeId == RECORDOID &&
  		ISCOMPLEX(inputTypeId))
  	{
  		/* Coerce a specific complex type to RECORD */
  		/* NB: we do NOT want a RelabelType here */
  		return node;
  	}
  #ifdef NOT_USED
  	if (inputTypeId == RECORDARRAYOID &&
  		is_complex_array(targetTypeId))
  	{
  		/* Coerce record[] to a specific complex array type */
  		/* not implemented yet ... */
  	}
  #endif
  	if (targetTypeId == RECORDARRAYOID &&
  		is_complex_array(inputTypeId))
  	{
  		/* Coerce a specific complex array type to record[] */
  		/* NB: we do NOT want a RelabelType here */
  		return node;
  	}
  	if (typeInheritsFrom(inputTypeId, targetTypeId)
  		|| typeIsOfTypedTable(inputTypeId, targetTypeId))
  	{
  		/*
  		 * Input class type is a subclass of target, so generate an
  		 * appropriate runtime conversion (removing unneeded columns and
  		 * possibly rearranging the ones that are wanted).
  		 *
  		 * We will also get here when the input is a domain over a subclass of
  		 * the target type.  To keep life simple for the executor, we define
  		 * ConvertRowtypeExpr as only working between regular composite types;
  		 * therefore, in such cases insert a RelabelType to smash the input
  		 * expression down to its base type.
  		 */
  		Oid			baseTypeId = getBaseType(inputTypeId);
  		ConvertRowtypeExpr *r = makeNode(ConvertRowtypeExpr);
  
  		if (baseTypeId != inputTypeId)
  		{
  			RelabelType *rt = makeRelabelType((Expr *) node,
  											  baseTypeId, -1,
  											  InvalidOid,
  											  COERCE_IMPLICIT_CAST);
  
  			rt->location = location;
  			node = (Node *) rt;
  		}
  		r->arg = (Expr *) node;
  		r->resulttype = targetTypeId;
  		r->convertformat = cformat;
  		r->location = location;
  		return (Node *) r;
  	}
  	/* If we get here, caller blew it */
  	elog(ERROR, "failed to find conversion function from %s to %s",
  		 format_type_be(inputTypeId), format_type_be(targetTypeId));
  	return NULL;				/* keep compiler quiet */
  }
  
  
  /*
   * can_coerce_type()
   *		Can input_typeids be coerced to target_typeids?
   *
   * We must be told the context (CAST construct, assignment, implicit coercion)
   * as this determines the set of available casts.
   */
  bool
  can_coerce_type(int nargs, const Oid *input_typeids, const Oid *target_typeids,
  				CoercionContext ccontext)
  {
  	bool		have_generics = false;
  	int			i;
  
  	/* run through argument list... */
  	for (i = 0; i < nargs; i++)
  	{
  		Oid			inputTypeId = input_typeids[i];
  		Oid			targetTypeId = target_typeids[i];
  		CoercionPathType pathtype;
  		Oid			funcId;
  
  		/* no problem if same type */
  		if (inputTypeId == targetTypeId)
  			continue;
  
  		/* accept if target is ANY */
  		if (targetTypeId == ANYOID)
  			continue;
  
  		/* accept if target is polymorphic, for now */
  		if (IsPolymorphicType(targetTypeId))
  		{
  			have_generics = true;	/* do more checking later */
  			continue;
  		}
  
  		/*
  		 * If input is an untyped string constant, assume we can convert it to
  		 * anything.
  		 */
  		if (inputTypeId == UNKNOWNOID)
  			continue;
  
  		/*
  		 * If pg_cast shows that we can coerce, accept.  This test now covers
  		 * both binary-compatible and coercion-function cases.
  		 */
  		pathtype = find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
  										 &funcId);
  		if (pathtype != COERCION_PATH_NONE)
  			continue;
  
  		/*
  		 * If input is RECORD and target is a composite type, assume we can
  		 * coerce (may need tighter checking here)
  		 */
  		if (inputTypeId == RECORDOID &&
  			ISCOMPLEX(targetTypeId))
  			continue;
  
  		/*
  		 * If input is a composite type and target is RECORD, accept
  		 */
  		if (targetTypeId == RECORDOID &&
  			ISCOMPLEX(inputTypeId))
  			continue;
  
  #ifdef NOT_USED					/* not implemented yet */
  
  		/*
  		 * If input is record[] and target is a composite array type, assume
  		 * we can coerce (may need tighter checking here)
  		 */
  		if (inputTypeId == RECORDARRAYOID &&
  			is_complex_array(targetTypeId))
  			continue;
  #endif
  
  		/*
  		 * If input is a composite array type and target is record[], accept
  		 */
  		if (targetTypeId == RECORDARRAYOID &&
  			is_complex_array(inputTypeId))
  			continue;
  
  		/*
  		 * If input is a class type that inherits from target, accept
  		 */
  		if (typeInheritsFrom(inputTypeId, targetTypeId)
  			|| typeIsOfTypedTable(inputTypeId, targetTypeId))
  			continue;
  
  		/*
  		 * Else, cannot coerce at this argument position
  		 */
  		return false;
  	}
  
  	/* If we found any generic argument types, cross-check them */
  	if (have_generics)
  	{
  		if (!check_generic_type_consistency(input_typeids, target_typeids,
  											nargs))
  			return false;
  	}
  
  	return true;
  }
  
  
  /*
   * Create an expression tree to represent coercion to a domain type.
   *
   * 'arg': input expression
   * 'baseTypeId': base type of domain, if known (pass InvalidOid if caller
   *		has not bothered to look this up)
   * 'baseTypeMod': base type typmod of domain, if known (pass -1 if caller
   *		has not bothered to look this up)
   * 'typeId': target type to coerce to
   * 'ccontext': context indicator to control coercions
   * 'cformat': coercion display format
   * 'location': coercion request location
   * 'hideInputCoercion': if true, hide the input coercion under this one.
   *
   * If the target type isn't a domain, the given 'arg' is returned as-is.
   */
  Node *
  coerce_to_domain(Node *arg, Oid baseTypeId, int32 baseTypeMod, Oid typeId,
  				 CoercionContext ccontext, CoercionForm cformat, int location,
  				 bool hideInputCoercion)
  {
  	CoerceToDomain *result;
  
  	/* Get the base type if it hasn't been supplied */
  	if (baseTypeId == InvalidOid)
  		baseTypeId = getBaseTypeAndTypmod(typeId, &baseTypeMod);
  
  	/* If it isn't a domain, return the node as it was passed in */
  	if (baseTypeId == typeId)
  		return arg;
  
  	/* Suppress display of nested coercion steps */
  	if (hideInputCoercion)
  		hide_coercion_node(arg);
  
  	/*
  	 * If the domain applies a typmod to its base type, build the appropriate
  	 * coercion step.  Mark it implicit for display purposes, because we don't
  	 * want it shown separately by ruleutils.c; but the isExplicit flag passed
  	 * to the conversion function depends on the manner in which the domain
  	 * coercion is invoked, so that the semantics of implicit and explicit
  	 * coercion differ.  (Is that really the behavior we want?)
  	 *
  	 * NOTE: because we apply this as part of the fixed expression structure,
  	 * ALTER DOMAIN cannot alter the typtypmod.  But it's unclear that that
  	 * would be safe to do anyway, without lots of knowledge about what the
  	 * base type thinks the typmod means.
  	 */
  	arg = coerce_type_typmod(arg, baseTypeId, baseTypeMod,
  							 ccontext, COERCE_IMPLICIT_CAST, location,
  							 false);
  
  	/*
  	 * Now build the domain coercion node.  This represents run-time checking
  	 * of any constraints currently attached to the domain.  This also ensures
  	 * that the expression is properly labeled as to result type.
  	 */
  	result = makeNode(CoerceToDomain);
  	result->arg = (Expr *) arg;
  	result->resulttype = typeId;
  	result->resulttypmod = -1;	/* currently, always -1 for domains */
  	/* resultcollid will be set by parse_collate.c */
  	result->coercionformat = cformat;
  	result->location = location;
  
  	return (Node *) result;
  }
  
  
  /*
   * coerce_type_typmod()
   *		Force a value to a particular typmod, if meaningful and possible.
   *
   * This is applied to values that are going to be stored in a relation
   * (where we have an atttypmod for the column) as well as values being
   * explicitly CASTed (where the typmod comes from the target type spec).
   *
   * The caller must have already ensured that the value is of the correct
   * type, typically by applying coerce_type.
   *
   * ccontext may affect semantics, depending on whether the length coercion
   * function pays attention to the isExplicit flag it's passed.
   *
   * cformat determines the display properties of the generated node (if any).
   *
   * If hideInputCoercion is true *and* we generate a node, the input node is
   * forced to IMPLICIT display form, so that only the typmod coercion node will
   * be visible when displaying the expression.
   *
   * NOTE: this does not need to work on domain types, because any typmod
   * coercion for a domain is considered to be part of the type coercion
   * needed to produce the domain value in the first place.  So, no getBaseType.
   */
  static Node *
  coerce_type_typmod(Node *node, Oid targetTypeId, int32 targetTypMod,
  				   CoercionContext ccontext, CoercionForm cformat,
  				   int location,
  				   bool hideInputCoercion)
  {
  	CoercionPathType pathtype;
  	Oid			funcId;
  
  	/* Skip coercion if already done */
  	if (targetTypMod == exprTypmod(node))
  		return node;
  
  	/* Suppress display of nested coercion steps */
  	if (hideInputCoercion)
  		hide_coercion_node(node);
  
  	pathtype = find_typmod_coercion_function(targetTypeId, &funcId);
  
  	if (pathtype != COERCION_PATH_NONE)
  	{
  		node = build_coercion_expression(node, pathtype, funcId,
  										 targetTypeId, targetTypMod,
  										 ccontext, cformat, location);
  	}
  	else
  	{
  		/*
  		 * We don't need to perform any actual coercion step, but we should
  		 * apply a RelabelType to ensure that the expression exposes the
  		 * intended typmod.
  		 */
  		node = applyRelabelType(node, targetTypeId, targetTypMod,
  								exprCollation(node),
  								cformat, location, false);
  	}
  
  	return node;
  }
  
  /*
   * Mark a coercion node as IMPLICIT so it will never be displayed by
   * ruleutils.c.  We use this when we generate a nest of coercion nodes
   * to implement what is logically one conversion; the inner nodes are
   * forced to IMPLICIT_CAST format.  This does not change their semantics,
   * only display behavior.
   *
   * It is caller error to call this on something that doesn't have a
   * CoercionForm field.
   */
  static void
  hide_coercion_node(Node *node)
  {
  	if (IsA(node, FuncExpr))
  		((FuncExpr *) node)->funcformat = COERCE_IMPLICIT_CAST;
  	else if (IsA(node, RelabelType))
  		((RelabelType *) node)->relabelformat = COERCE_IMPLICIT_CAST;
  	else if (IsA(node, CoerceViaIO))
  		((CoerceViaIO *) node)->coerceformat = COERCE_IMPLICIT_CAST;
  	else if (IsA(node, ArrayCoerceExpr))
  		((ArrayCoerceExpr *) node)->coerceformat = COERCE_IMPLICIT_CAST;
  	else if (IsA(node, ConvertRowtypeExpr))
  		((ConvertRowtypeExpr *) node)->convertformat = COERCE_IMPLICIT_CAST;
  	else if (IsA(node, RowExpr))
  		((RowExpr *) node)->row_format = COERCE_IMPLICIT_CAST;
  	else if (IsA(node, CoerceToDomain))
  		((CoerceToDomain *) node)->coercionformat = COERCE_IMPLICIT_CAST;
  	else
  		elog(ERROR, "unsupported node type: %d", (int) nodeTag(node));
  }
  
  /*
   * build_coercion_expression()
   *		Construct an expression tree for applying a pg_cast entry.
   *
   * This is used for both type-coercion and length-coercion operations,
   * since there is no difference in terms of the calling convention.
   */
  static Node *
  build_coercion_expression(Node *node,
  						  CoercionPathType pathtype,
  						  Oid funcId,
  						  Oid targetTypeId, int32 targetTypMod,
  						  CoercionContext ccontext, CoercionForm cformat,
  						  int location)
  {
  	int			nargs = 0;
  
  	if (OidIsValid(funcId))
  	{
  		HeapTuple	tp;
  		Form_pg_proc procstruct;
  
  		tp = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcId));
  		if (!HeapTupleIsValid(tp))
  			elog(ERROR, "cache lookup failed for function %u", funcId);
  		procstruct = (Form_pg_proc) GETSTRUCT(tp);
  
  		/*
  		 * These Asserts essentially check that function is a legal coercion
  		 * function.  We can't make the seemingly obvious tests on prorettype
  		 * and proargtypes[0], even in the COERCION_PATH_FUNC case, because of
  		 * various binary-compatibility cases.
  		 */
  		/* Assert(targetTypeId == procstruct->prorettype); */
  		Assert(!procstruct->proretset);
  		Assert(procstruct->prokind == PROKIND_FUNCTION);
  		nargs = procstruct->pronargs;
  		Assert(nargs >= 1 && nargs <= 3);
  		/* Assert(procstruct->proargtypes.values[0] == exprType(node)); */
  		Assert(nargs < 2 || procstruct->proargtypes.values[1] == INT4OID);
  		Assert(nargs < 3 || procstruct->proargtypes.values[2] == BOOLOID);
  
  		ReleaseSysCache(tp);
  	}
  
  	if (pathtype == COERCION_PATH_FUNC)
  	{
  		/* We build an ordinary FuncExpr with special arguments */
  		FuncExpr   *fexpr;
  		List	   *args;
  		Const	   *cons;
  
  		Assert(OidIsValid(funcId));
  
  		args = list_make1(node);
  
  		if (nargs >= 2)
  		{
  			/* Pass target typmod as an int4 constant */
  			cons = makeConst(INT4OID,
  							 -1,
  							 InvalidOid,
  							 sizeof(int32),
  							 Int32GetDatum(targetTypMod),
  							 false,
  							 true);
  
  			args = lappend(args, cons);
  		}
  
  		if (nargs == 3)
  		{
  			/* Pass it a boolean isExplicit parameter, too */
  			cons = makeConst(BOOLOID,
  							 -1,
  							 InvalidOid,
  							 sizeof(bool),
  							 BoolGetDatum(ccontext == COERCION_EXPLICIT),
  							 false,
  							 true);
  
  			args = lappend(args, cons);
  		}
  
  		fexpr = makeFuncExpr(funcId, targetTypeId, args,
  							 InvalidOid, InvalidOid, cformat);
  		fexpr->location = location;
  		return (Node *) fexpr;
  	}
  	else if (pathtype == COERCION_PATH_ARRAYCOERCE)
  	{
  		/* We need to build an ArrayCoerceExpr */
  		ArrayCoerceExpr *acoerce = makeNode(ArrayCoerceExpr);
  		CaseTestExpr *ctest = makeNode(CaseTestExpr);
  		Oid			sourceBaseTypeId;
  		int32		sourceBaseTypeMod;
  		Oid			targetElementType;
  		Node	   *elemexpr;
  
  		/*
  		 * Look through any domain over the source array type.  Note we don't
  		 * expect that the target type is a domain; it must be a plain array.
  		 * (To get to a domain target type, we'll do coerce_to_domain later.)
  		 */
  		sourceBaseTypeMod = exprTypmod(node);
  		sourceBaseTypeId = getBaseTypeAndTypmod(exprType(node),
  												&sourceBaseTypeMod);
  
  		/*
  		 * Set up a CaseTestExpr representing one element of the source array.
  		 * This is an abuse of CaseTestExpr, but it's OK as long as there
  		 * can't be any CaseExpr or ArrayCoerceExpr within the completed
  		 * elemexpr.
  		 */
  		ctest->typeId = get_element_type(sourceBaseTypeId);
  		Assert(OidIsValid(ctest->typeId));
  		ctest->typeMod = sourceBaseTypeMod;
  		ctest->collation = InvalidOid;	/* Assume coercions don't care */
  
  		/* And coerce it to the target element type */
  		targetElementType = get_element_type(targetTypeId);
  		Assert(OidIsValid(targetElementType));
  
  		elemexpr = coerce_to_target_type(NULL,
  										 (Node *) ctest,
  										 ctest->typeId,
  										 targetElementType,
  										 targetTypMod,
  										 ccontext,
  										 cformat,
  										 location);
  		if (elemexpr == NULL)	/* shouldn't happen */
  			elog(ERROR, "failed to coerce array element type as expected");
  
  		acoerce->arg = (Expr *) node;
  		acoerce->elemexpr = (Expr *) elemexpr;
  		acoerce->resulttype = targetTypeId;
  
  		/*
  		 * Label the output as having a particular element typmod only if we
  		 * ended up with a per-element expression that is labeled that way.
  		 */
  		acoerce->resulttypmod = exprTypmod(elemexpr);
  		/* resultcollid will be set by parse_collate.c */
  		acoerce->coerceformat = cformat;
  		acoerce->location = location;
  
  		return (Node *) acoerce;
  	}
  	else if (pathtype == COERCION_PATH_COERCEVIAIO)
  	{
  		/* We need to build a CoerceViaIO node */
  		CoerceViaIO *iocoerce = makeNode(CoerceViaIO);
  
  		Assert(!OidIsValid(funcId));
  
  		iocoerce->arg = (Expr *) node;
  		iocoerce->resulttype = targetTypeId;
  		/* resultcollid will be set by parse_collate.c */
  		iocoerce->coerceformat = cformat;
  		iocoerce->location = location;
  
  		return (Node *) iocoerce;
  	}
  	else
  	{
  		elog(ERROR, "unsupported pathtype %d in build_coercion_expression",
  			 (int) pathtype);
  		return NULL;			/* keep compiler quiet */
  	}
  }
  
  
  /*
   * coerce_record_to_complex
   *		Coerce a RECORD to a specific composite type.
   *
   * Currently we only support this for inputs that are RowExprs or whole-row
   * Vars.
   */
  static Node *
  coerce_record_to_complex(ParseState *pstate, Node *node,
  						 Oid targetTypeId,
  						 CoercionContext ccontext,
  						 CoercionForm cformat,
  						 int location)
  {
  	RowExpr    *rowexpr;
  	Oid			baseTypeId;
  	int32		baseTypeMod = -1;
  	TupleDesc	tupdesc;
  	List	   *args = NIL;
  	List	   *newargs;
  	int			i;
  	int			ucolno;
  	ListCell   *arg;
  
  	if (node && IsA(node, RowExpr))
  	{
  		/*
  		 * Since the RowExpr must be of type RECORD, we needn't worry about it
  		 * containing any dropped columns.
  		 */
  		args = ((RowExpr *) node)->args;
  	}
  	else if (node && IsA(node, Var) &&
  			 ((Var *) node)->varattno == InvalidAttrNumber)
  	{
  		int			rtindex = ((Var *) node)->varno;
  		int			sublevels_up = ((Var *) node)->varlevelsup;
  		int			vlocation = ((Var *) node)->location;
  		ParseNamespaceItem *nsitem;
  
  		nsitem = GetNSItemByRangeTablePosn(pstate, rtindex, sublevels_up);
  		args = expandNSItemVars(nsitem, sublevels_up, vlocation, NULL);
  	}
  	else
  		ereport(ERROR,
  				(errcode(ERRCODE_CANNOT_COERCE),
  				 errmsg("cannot cast type %s to %s",
  						format_type_be(RECORDOID),
  						format_type_be(targetTypeId)),
  				 parser_coercion_errposition(pstate, location, node)));
  
  	/*
  	 * Look up the composite type, accounting for possibility that what we are
  	 * given is a domain over composite.
  	 */
  	baseTypeId = getBaseTypeAndTypmod(targetTypeId, &baseTypeMod);
  	tupdesc = lookup_rowtype_tupdesc(baseTypeId, baseTypeMod);
  
  	/* Process the fields */
  	newargs = NIL;
  	ucolno = 1;
  	arg = list_head(args);
  	for (i = 0; i < tupdesc->natts; i++)
  	{
  		Node	   *expr;
  		Node	   *cexpr;
  		Oid			exprtype;
  		Form_pg_attribute attr = TupleDescAttr(tupdesc, i);
  
  		/* Fill in NULLs for dropped columns in rowtype */
  		if (attr->attisdropped)
  		{
  			/*
  			 * can't use atttypid here, but it doesn't really matter what type
  			 * the Const claims to be.
  			 */
  			newargs = lappend(newargs,
  							  makeNullConst(INT4OID, -1, InvalidOid));
  			continue;
  		}
  
  		if (arg == NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_CANNOT_COERCE),
  					 errmsg("cannot cast type %s to %s",
  							format_type_be(RECORDOID),
  							format_type_be(targetTypeId)),
  					 errdetail("Input has too few columns."),
  					 parser_coercion_errposition(pstate, location, node)));
  		expr = (Node *) lfirst(arg);
  		exprtype = exprType(expr);
  
  		cexpr = coerce_to_target_type(pstate,
  									  expr, exprtype,
  									  attr->atttypid,
  									  attr->atttypmod,
  									  ccontext,
  									  COERCE_IMPLICIT_CAST,
  									  -1);
  		if (cexpr == NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_CANNOT_COERCE),
  					 errmsg("cannot cast type %s to %s",
  							format_type_be(RECORDOID),
  							format_type_be(targetTypeId)),
  					 errdetail("Cannot cast type %s to %s in column %d.",
  							   format_type_be(exprtype),
  							   format_type_be(attr->atttypid),
  							   ucolno),
  					 parser_coercion_errposition(pstate, location, expr)));
  		newargs = lappend(newargs, cexpr);
  		ucolno++;
  		arg = lnext(args, arg);
  	}
  	if (arg != NULL)
  		ereport(ERROR,
  				(errcode(ERRCODE_CANNOT_COERCE),
  				 errmsg("cannot cast type %s to %s",
  						format_type_be(RECORDOID),
  						format_type_be(targetTypeId)),
  				 errdetail("Input has too many columns."),
  				 parser_coercion_errposition(pstate, location, node)));
  
  	ReleaseTupleDesc(tupdesc);
  
  	rowexpr = makeNode(RowExpr);
  	rowexpr->args = newargs;
  	rowexpr->row_typeid = baseTypeId;
  	rowexpr->row_format = cformat;
  	rowexpr->colnames = NIL;	/* not needed for named target type */
  	rowexpr->location = location;
  
  	/* If target is a domain, apply constraints */
  	if (baseTypeId != targetTypeId)
  	{
  		rowexpr->row_format = COERCE_IMPLICIT_CAST;
  		return coerce_to_domain((Node *) rowexpr,
  								baseTypeId, baseTypeMod,
  								targetTypeId,
  								ccontext, cformat, location,
  								false);
  	}
  
  	return (Node *) rowexpr;
  }
  
  /*
   * coerce_to_boolean()
   *		Coerce an argument of a construct that requires boolean input
   *		(AND, OR, NOT, etc).  Also check that input is not a set.
   *
   * Returns the possibly-transformed node tree.
   *
   * As with coerce_type, pstate may be NULL if no special unknown-Param
   * processing is wanted.
   */
  Node *
  coerce_to_boolean(ParseState *pstate, Node *node,
  				  const char *constructName)
  {
  	Oid			inputTypeId = exprType(node);
  
  	if (inputTypeId != BOOLOID)
  	{
  		Node	   *newnode;
  
  		newnode = coerce_to_target_type(pstate, node, inputTypeId,
  										BOOLOID, -1,
  										COERCION_ASSIGNMENT,
  										COERCE_IMPLICIT_CAST,
  										-1);
  		if (newnode == NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  			/* translator: first %s is name of a SQL construct, eg WHERE */
  					 errmsg("argument of %s must be type %s, not type %s",
  							constructName, "boolean",
  							format_type_be(inputTypeId)),
  					 parser_errposition(pstate, exprLocation(node))));
  		node = newnode;
  	}
  
  	if (expression_returns_set(node))
  		ereport(ERROR,
  				(errcode(ERRCODE_DATATYPE_MISMATCH),
  		/* translator: %s is name of a SQL construct, eg WHERE */
  				 errmsg("argument of %s must not return a set",
  						constructName),
  				 parser_errposition(pstate, exprLocation(node))));
  
  	return node;
  }
  
  /*
   * coerce_to_specific_type_typmod()
   *		Coerce an argument of a construct that requires a specific data type,
   *		with a specific typmod.  Also check that input is not a set.
   *
   * Returns the possibly-transformed node tree.
   *
   * As with coerce_type, pstate may be NULL if no special unknown-Param
   * processing is wanted.
   */
  Node *
  coerce_to_specific_type_typmod(ParseState *pstate, Node *node,
  							   Oid targetTypeId, int32 targetTypmod,
  							   const char *constructName)
  {
  	Oid			inputTypeId = exprType(node);
  
  	if (inputTypeId != targetTypeId)
  	{
  		Node	   *newnode;
  
  		newnode = coerce_to_target_type(pstate, node, inputTypeId,
  										targetTypeId, targetTypmod,
  										COERCION_ASSIGNMENT,
  										COERCE_IMPLICIT_CAST,
  										-1);
  		if (newnode == NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  			/* translator: first %s is name of a SQL construct, eg LIMIT */
  					 errmsg("argument of %s must be type %s, not type %s",
  							constructName,
  							format_type_be(targetTypeId),
  							format_type_be(inputTypeId)),
  					 parser_errposition(pstate, exprLocation(node))));
  		node = newnode;
  	}
  
  	if (expression_returns_set(node))
  		ereport(ERROR,
  				(errcode(ERRCODE_DATATYPE_MISMATCH),
  		/* translator: %s is name of a SQL construct, eg LIMIT */
  				 errmsg("argument of %s must not return a set",
  						constructName),
  				 parser_errposition(pstate, exprLocation(node))));
  
  	return node;
  }
  
  /*
   * coerce_to_specific_type()
   *		Coerce an argument of a construct that requires a specific data type.
   *		Also check that input is not a set.
   *
   * Returns the possibly-transformed node tree.
   *
   * As with coerce_type, pstate may be NULL if no special unknown-Param
   * processing is wanted.
   */
  Node *
  coerce_to_specific_type(ParseState *pstate, Node *node,
  						Oid targetTypeId,
  						const char *constructName)
  {
  	return coerce_to_specific_type_typmod(pstate, node,
  										  targetTypeId, -1,
  										  constructName);
  }
  
  /*
   * parser_coercion_errposition - report coercion error location, if possible
   *
   * We prefer to point at the coercion request (CAST, ::, etc) if possible;
   * but there may be no such location in the case of an implicit coercion.
   * In that case point at the input expression.
   *
   * XXX possibly this is more generally useful than coercion errors;
   * if so, should rename and place with parser_errposition.
   */
  int
  parser_coercion_errposition(ParseState *pstate,
  							int coerce_location,
  							Node *input_expr)
  {
  	if (coerce_location >= 0)
  		return parser_errposition(pstate, coerce_location);
  	else
  		return parser_errposition(pstate, exprLocation(input_expr));
  }
  
  
  /*
   * select_common_type()
   *		Determine the common supertype of a list of input expressions.
   *		This is used for determining the output type of CASE, UNION,
   *		and similar constructs.
   *
   * 'exprs' is a *nonempty* list of expressions.  Note that earlier items
   * in the list will be preferred if there is doubt.
   * 'context' is a phrase to use in the error message if we fail to select
   * a usable type.  Pass NULL to have the routine return InvalidOid
   * rather than throwing an error on failure.
   * 'which_expr': if not NULL, receives a pointer to the particular input
   * expression from which the result type was taken.
   */
  Oid
  select_common_type(ParseState *pstate, List *exprs, const char *context,
  				   Node **which_expr)
  {
  	Node	   *pexpr;
  	Oid			ptype;
  	TYPCATEGORY pcategory;
  	bool		pispreferred;
  	ListCell   *lc;
  
  	Assert(exprs != NIL);
  	pexpr = (Node *) linitial(exprs);
  	lc = list_second_cell(exprs);
  	ptype = exprType(pexpr);
  
  	/*
  	 * If all input types are valid and exactly the same, just pick that type.
  	 * This is the only way that we will resolve the result as being a domain
  	 * type; otherwise domains are smashed to their base types for comparison.
  	 */
  	if (ptype != UNKNOWNOID)
  	{
  		for_each_cell(lc, exprs, lc)
  		{
  			Node	   *nexpr = (Node *) lfirst(lc);
  			Oid			ntype = exprType(nexpr);
  
  			if (ntype != ptype)
  				break;
  		}
  		if (lc == NULL)			/* got to the end of the list? */
  		{
  			if (which_expr)
  				*which_expr = pexpr;
  			return ptype;
  		}
  	}
  
  	/*
  	 * Nope, so set up for the full algorithm.  Note that at this point, lc
  	 * points to the first list item with type different from pexpr's; we need
  	 * not re-examine any items the previous loop advanced over.
  	 */
  	ptype = getBaseType(ptype);
  	get_type_category_preferred(ptype, &pcategory, &pispreferred);
  
  	for_each_cell(lc, exprs, lc)
  	{
  		Node	   *nexpr = (Node *) lfirst(lc);
  		Oid			ntype = getBaseType(exprType(nexpr));
  
  		/* move on to next one if no new information... */
  		if (ntype != UNKNOWNOID && ntype != ptype)
  		{
  			TYPCATEGORY ncategory;
  			bool		nispreferred;
  
  			get_type_category_preferred(ntype, &ncategory, &nispreferred);
  			if (ptype == UNKNOWNOID)
  			{
  				/* so far, only unknowns so take anything... */
  				pexpr = nexpr;
  				ptype = ntype;
  				pcategory = ncategory;
  				pispreferred = nispreferred;
  			}
  			else if (ncategory != pcategory)
  			{
  				/*
  				 * both types in different categories? then not much hope...
  				 */
  				if (context == NULL)
  					return InvalidOid;
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  				/*------
  				  translator: first %s is name of a SQL construct, eg CASE */
  						 errmsg("%s types %s and %s cannot be matched",
  								context,
  								format_type_be(ptype),
  								format_type_be(ntype)),
  						 parser_errposition(pstate, exprLocation(nexpr))));
  			}
  			else if (!pispreferred &&
  					 can_coerce_type(1, &ptype, &ntype, COERCION_IMPLICIT) &&
  					 !can_coerce_type(1, &ntype, &ptype, COERCION_IMPLICIT))
  			{
  				/*
  				 * take new type if can coerce to it implicitly but not the
  				 * other way; but if we have a preferred type, stay on it.
  				 */
  				pexpr = nexpr;
  				ptype = ntype;
  				pcategory = ncategory;
  				pispreferred = nispreferred;
  			}
  		}
  	}
  
  	/*
  	 * If all the inputs were UNKNOWN type --- ie, unknown-type literals ---
  	 * then resolve as type TEXT.  This situation comes up with constructs
  	 * like SELECT (CASE WHEN foo THEN 'bar' ELSE 'baz' END); SELECT 'foo'
  	 * UNION SELECT 'bar'; It might seem desirable to leave the construct's
  	 * output type as UNKNOWN, but that really doesn't work, because we'd
  	 * probably end up needing a runtime coercion from UNKNOWN to something
  	 * else, and we usually won't have it.  We need to coerce the unknown
  	 * literals while they are still literals, so a decision has to be made
  	 * now.
  	 */
  	if (ptype == UNKNOWNOID)
  		ptype = TEXTOID;
  
  	if (which_expr)
  		*which_expr = pexpr;
  	return ptype;
  }
  
  /*
   * select_common_type_from_oids()
   *		Determine the common supertype of an array of type OIDs.
   *
   * This is the same logic as select_common_type(), but working from
   * an array of type OIDs not a list of expressions.  As in that function,
   * earlier entries in the array have some preference over later ones.
   * On failure, return InvalidOid if noerror is true, else throw an error.
   *
   * Note: neither caller will pass any UNKNOWNOID entries, so the tests
   * for that in this function are dead code.  However, they don't cost much,
   * and it seems better to keep this logic as close to select_common_type()
   * as possible.
   */
  static Oid
  select_common_type_from_oids(int nargs, const Oid *typeids, bool noerror)
  {
  	Oid			ptype;
  	TYPCATEGORY pcategory;
  	bool		pispreferred;
  	int			i = 1;
  
  	Assert(nargs > 0);
  	ptype = typeids[0];
  
  	/* If all input types are valid and exactly the same, pick that type. */
  	if (ptype != UNKNOWNOID)
  	{
  		for (; i < nargs; i++)
  		{
  			if (typeids[i] != ptype)
  				break;
  		}
  		if (i == nargs)
  			return ptype;
  	}
  
  	/*
  	 * Nope, so set up for the full algorithm.  Note that at this point, we
  	 * can skip array entries before "i"; they are all equal to ptype.
  	 */
  	ptype = getBaseType(ptype);
  	get_type_category_preferred(ptype, &pcategory, &pispreferred);
  
  	for (; i < nargs; i++)
  	{
  		Oid			ntype = getBaseType(typeids[i]);
  
  		/* move on to next one if no new information... */
  		if (ntype != UNKNOWNOID && ntype != ptype)
  		{
  			TYPCATEGORY ncategory;
  			bool		nispreferred;
  
  			get_type_category_preferred(ntype, &ncategory, &nispreferred);
  			if (ptype == UNKNOWNOID)
  			{
  				/* so far, only unknowns so take anything... */
  				ptype = ntype;
  				pcategory = ncategory;
  				pispreferred = nispreferred;
  			}
  			else if (ncategory != pcategory)
  			{
  				/*
  				 * both types in different categories? then not much hope...
  				 */
  				if (noerror)
  					return InvalidOid;
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument types %s and %s cannot be matched",
  								format_type_be(ptype),
  								format_type_be(ntype))));
  			}
  			else if (!pispreferred &&
  					 can_coerce_type(1, &ptype, &ntype, COERCION_IMPLICIT) &&
  					 !can_coerce_type(1, &ntype, &ptype, COERCION_IMPLICIT))
  			{
  				/*
  				 * take new type if can coerce to it implicitly but not the
  				 * other way; but if we have a preferred type, stay on it.
  				 */
  				ptype = ntype;
  				pcategory = ncategory;
  				pispreferred = nispreferred;
  			}
  		}
  	}
  
  	/* Like select_common_type(), choose TEXT if all inputs were UNKNOWN */
  	if (ptype == UNKNOWNOID)
  		ptype = TEXTOID;
  
  	return ptype;
  }
  
  /*
   * coerce_to_common_type()
   *		Coerce an expression to the given type.
   *
   * This is used following select_common_type() to coerce the individual
   * expressions to the desired type.  'context' is a phrase to use in the
   * error message if we fail to coerce.
   *
   * As with coerce_type, pstate may be NULL if no special unknown-Param
   * processing is wanted.
   */
  Node *
  coerce_to_common_type(ParseState *pstate, Node *node,
  					  Oid targetTypeId, const char *context)
  {
  	Oid			inputTypeId = exprType(node);
  
  	if (inputTypeId == targetTypeId)
  		return node;			/* no work */
  	if (can_coerce_type(1, &inputTypeId, &targetTypeId, COERCION_IMPLICIT))
  		node = coerce_type(pstate, node, inputTypeId, targetTypeId, -1,
  						   COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
  	else
  		ereport(ERROR,
  				(errcode(ERRCODE_CANNOT_COERCE),
  		/* translator: first %s is name of a SQL construct, eg CASE */
  				 errmsg("%s could not convert type %s to %s",
  						context,
  						format_type_be(inputTypeId),
  						format_type_be(targetTypeId)),
  				 parser_errposition(pstate, exprLocation(node))));
  	return node;
  }
  
  /*
   * select_common_typmod()
   *		Determine the common typmod of a list of input expressions.
   *
   * common_type is the selected common type of the expressions, typically
   * computed using select_common_type().
   */
  int32
  select_common_typmod(ParseState *pstate, List *exprs, Oid common_type)
  {
  	ListCell   *lc;
  	bool		first = true;
  	int32		result = -1;
  
  	foreach(lc, exprs)
  	{
  		Node	   *expr = (Node *) lfirst(lc);
  
  		/* Types must match */
  		if (exprType(expr) != common_type)
  			return -1;
  		else if (first)
  		{
  			result = exprTypmod(expr);
  			first = false;
  		}
  		else
  		{
  			/* As soon as we see a non-matching typmod, fall back to -1 */
  			if (result != exprTypmod(expr))
  				return -1;
  		}
  	}
  
  	return result;
  }
  
  /*
   * check_generic_type_consistency()
   *		Are the actual arguments potentially compatible with a
   *		polymorphic function?
   *
   * The argument consistency rules are:
   *
   * 1) All arguments declared ANYELEMENT must have the same datatype.
   * 2) All arguments declared ANYARRAY must have the same datatype,
   *	  which must be a varlena array type.
   * 3) All arguments declared ANYRANGE must be the same range type.
   *	  Similarly, all arguments declared ANYMULTIRANGE must be the same
   *	  multirange type; and if both of these appear, the ANYRANGE type
   *	  must be the element type of the ANYMULTIRANGE type.
   * 4) If there are arguments of more than one of these polymorphic types,
   *	  the array element type and/or range subtype must be the same as each
   *	  other and the same as the ANYELEMENT type.
   * 5) ANYENUM is treated the same as ANYELEMENT except that if it is used
   *	  (alone or in combination with plain ANYELEMENT), we add the extra
   *	  condition that the ANYELEMENT type must be an enum.
   * 6) ANYNONARRAY is treated the same as ANYELEMENT except that if it is used,
   *	  we add the extra condition that the ANYELEMENT type must not be an array.
   *	  (This is a no-op if used in combination with ANYARRAY or ANYENUM, but
   *	  is an extra restriction if not.)
   * 7) All arguments declared ANYCOMPATIBLE must be implicitly castable
   *	  to a common supertype (chosen as per select_common_type's rules).
   *	  ANYCOMPATIBLENONARRAY works like ANYCOMPATIBLE but also requires the
   *	  common supertype to not be an array.  If there are ANYCOMPATIBLEARRAY
   *	  or ANYCOMPATIBLERANGE or ANYCOMPATIBLEMULTIRANGE arguments, their element
   *	  types or subtypes are included while making the choice of common supertype.
   * 8) The resolved type of ANYCOMPATIBLEARRAY arguments will be the array
   *	  type over the common supertype (which might not be the same array type
   *	  as any of the original arrays).
   * 9) All ANYCOMPATIBLERANGE arguments must be the exact same range type
   *	  (after domain flattening), since we have no preference rule that would
   *	  let us choose one over another.  Furthermore, that range's subtype
   *	  must exactly match the common supertype chosen by rule 7.
   * 10) All ANYCOMPATIBLEMULTIRANGE arguments must be the exact same multirange
   *	  type (after domain flattening), since we have no preference rule that
   *	  would let us choose one over another.  Furthermore, if ANYCOMPATIBLERANGE
   *	  also appears, that range type must be the multirange's element type;
   *	  otherwise, the multirange's range's subtype must exactly match the
   *	  common supertype chosen by rule 7.
   *
   * Domains over arrays match ANYARRAY, and are immediately flattened to their
   * base type.  (Thus, for example, we will consider it a match if one ANYARRAY
   * argument is a domain over int4[] while another one is just int4[].)	Also
   * notice that such a domain does *not* match ANYNONARRAY.  The same goes
   * for ANYCOMPATIBLEARRAY and ANYCOMPATIBLENONARRAY.
   *
   * Similarly, domains over ranges match ANYRANGE or ANYCOMPATIBLERANGE,
   * and are immediately flattened to their base type.  Likewise, domains
   * over multiranges match ANYMULTIRANGE or ANYCOMPATIBLEMULTIRANGE and are
   * immediately flattened to their base type.
   *
   * Note that domains aren't currently considered to match ANYENUM,
   * even if their base type would match.
   *
   * If we have UNKNOWN input (ie, an untyped literal) for any polymorphic
   * argument, assume it is okay.
   *
   * We do not ereport here, but just return false if a rule is violated.
   */
  bool
  check_generic_type_consistency(const Oid *actual_arg_types,
  							   const Oid *declared_arg_types,
  							   int nargs)
  {
  	Oid			elem_typeid = InvalidOid;
  	Oid			array_typeid = InvalidOid;
  	Oid			range_typeid = InvalidOid;
  	Oid			multirange_typeid = InvalidOid;
  	Oid			anycompatible_range_typeid = InvalidOid;
  	Oid			anycompatible_range_typelem = InvalidOid;
  	Oid			anycompatible_multirange_typeid = InvalidOid;
  	Oid			anycompatible_multirange_typelem = InvalidOid;
  	Oid			range_typelem = InvalidOid;
  	bool		have_anynonarray = false;
  	bool		have_anyenum = false;
  	bool		have_anycompatible_nonarray = false;
  	int			n_anycompatible_args = 0;
  	Oid			anycompatible_actual_types[FUNC_MAX_ARGS];
  
  	/*
  	 * Loop through the arguments to see if we have any that are polymorphic.
  	 * If so, require the actual types to be consistent.
  	 */
  	Assert(nargs <= FUNC_MAX_ARGS);
  	for (int j = 0; j < nargs; j++)
  	{
  		Oid			decl_type = declared_arg_types[j];
  		Oid			actual_type = actual_arg_types[j];
  
  		if (decl_type == ANYELEMENTOID ||
  			decl_type == ANYNONARRAYOID ||
  			decl_type == ANYENUMOID)
  		{
  			if (decl_type == ANYNONARRAYOID)
  				have_anynonarray = true;
  			else if (decl_type == ANYENUMOID)
  				have_anyenum = true;
  			if (actual_type == UNKNOWNOID)
  				continue;
  			if (OidIsValid(elem_typeid) && actual_type != elem_typeid)
  				return false;
  			elem_typeid = actual_type;
  		}
  		else if (decl_type == ANYARRAYOID)
  		{
  			if (actual_type == UNKNOWNOID)
  				continue;
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(array_typeid) && actual_type != array_typeid)
  				return false;
  			array_typeid = actual_type;
  		}
  		else if (decl_type == ANYRANGEOID)
  		{
  			if (actual_type == UNKNOWNOID)
  				continue;
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(range_typeid) && actual_type != range_typeid)
  				return false;
  			range_typeid = actual_type;
  		}
  		else if (decl_type == ANYMULTIRANGEOID)
  		{
  			if (actual_type == UNKNOWNOID)
  				continue;
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(multirange_typeid) && actual_type != multirange_typeid)
  				return false;
  			multirange_typeid = actual_type;
  		}
  		else if (decl_type == ANYCOMPATIBLEOID ||
  				 decl_type == ANYCOMPATIBLENONARRAYOID)
  		{
  			if (decl_type == ANYCOMPATIBLENONARRAYOID)
  				have_anycompatible_nonarray = true;
  			if (actual_type == UNKNOWNOID)
  				continue;
  			/* collect the actual types of non-unknown COMPATIBLE args */
  			anycompatible_actual_types[n_anycompatible_args++] = actual_type;
  		}
  		else if (decl_type == ANYCOMPATIBLEARRAYOID)
  		{
  			Oid			elem_type;
  
  			if (actual_type == UNKNOWNOID)
  				continue;
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			elem_type = get_element_type(actual_type);
  			if (!OidIsValid(elem_type))
  				return false;	/* not an array */
  			/* collect the element type for common-supertype choice */
  			anycompatible_actual_types[n_anycompatible_args++] = elem_type;
  		}
  		else if (decl_type == ANYCOMPATIBLERANGEOID)
  		{
  			if (actual_type == UNKNOWNOID)
  				continue;
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(anycompatible_range_typeid))
  			{
  				/* All ANYCOMPATIBLERANGE arguments must be the same type */
  				if (anycompatible_range_typeid != actual_type)
  					return false;
  			}
  			else
  			{
  				anycompatible_range_typeid = actual_type;
  				anycompatible_range_typelem = get_range_subtype(actual_type);
  				if (!OidIsValid(anycompatible_range_typelem))
  					return false;	/* not a range type */
  				/* collect the subtype for common-supertype choice */
  				anycompatible_actual_types[n_anycompatible_args++] = anycompatible_range_typelem;
  			}
  		}
  		else if (decl_type == ANYCOMPATIBLEMULTIRANGEOID)
  		{
  			if (actual_type == UNKNOWNOID)
  				continue;
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(anycompatible_multirange_typeid))
  			{
  				/* All ANYCOMPATIBLEMULTIRANGE arguments must be the same type */
  				if (anycompatible_multirange_typeid != actual_type)
  					return false;
  			}
  			else
  			{
  				anycompatible_multirange_typeid = actual_type;
  				anycompatible_multirange_typelem = get_multirange_range(actual_type);
  				if (!OidIsValid(anycompatible_multirange_typelem))
  					return false;	/* not a multirange type */
  				/* we'll consider the subtype below */
  			}
  		}
  	}
  
  	/* Get the element type based on the array type, if we have one */
  	if (OidIsValid(array_typeid))
  	{
  		if (array_typeid == ANYARRAYOID)
  		{
  			/*
  			 * Special case for matching ANYARRAY input to an ANYARRAY
  			 * argument: allow it for now.  enforce_generic_type_consistency()
  			 * might complain later, depending on the presence of other
  			 * polymorphic arguments or results, but it will deliver a less
  			 * surprising error message than "function does not exist".
  			 *
  			 * (If you think to change this, note that can_coerce_type will
  			 * consider such a situation as a match, so that we might not even
  			 * get here.)
  			 */
  		}
  		else
  		{
  			Oid			array_typelem;
  
  			array_typelem = get_element_type(array_typeid);
  			if (!OidIsValid(array_typelem))
  				return false;	/* should be an array, but isn't */
  
  			if (!OidIsValid(elem_typeid))
  			{
  				/*
  				 * if we don't have an element type yet, use the one we just
  				 * got
  				 */
  				elem_typeid = array_typelem;
  			}
  			else if (array_typelem != elem_typeid)
  			{
  				/* otherwise, they better match */
  				return false;
  			}
  		}
  	}
  
  	/* Deduce range type from multirange type, or check that they agree */
  	if (OidIsValid(multirange_typeid))
  	{
  		Oid			multirange_typelem;
  
  		multirange_typelem = get_multirange_range(multirange_typeid);
  		if (!OidIsValid(multirange_typelem))
  			return false;		/* should be a multirange, but isn't */
  
  		if (!OidIsValid(range_typeid))
  		{
  			/* If we don't have a range type yet, use the one we just got */
  			range_typeid = multirange_typelem;
  			range_typelem = get_range_subtype(multirange_typelem);
  			if (!OidIsValid(range_typelem))
  				return false;	/* should be a range, but isn't */
  		}
  		else if (multirange_typelem != range_typeid)
  		{
  			/* otherwise, they better match */
  			return false;
  		}
  	}
  
  	/* Get the element type based on the range type, if we have one */
  	if (OidIsValid(range_typeid))
  	{
  		range_typelem = get_range_subtype(range_typeid);
  		if (!OidIsValid(range_typelem))
  			return false;		/* should be a range, but isn't */
  
  		if (!OidIsValid(elem_typeid))
  		{
  			/*
  			 * If we don't have an element type yet, use the one we just got
  			 */
  			elem_typeid = range_typelem;
  		}
  		else if (range_typelem != elem_typeid)
  		{
  			/* otherwise, they better match */
  			return false;
  		}
  	}
  
  	if (have_anynonarray)
  	{
  		/* require the element type to not be an array or domain over array */
  		if (type_is_array_domain(elem_typeid))
  			return false;
  	}
  
  	if (have_anyenum)
  	{
  		/* require the element type to be an enum */
  		if (!type_is_enum(elem_typeid))
  			return false;
  	}
  
  	/* Deduce range type from multirange type, or check that they agree */
  	if (OidIsValid(anycompatible_multirange_typeid))
  	{
  		if (OidIsValid(anycompatible_range_typeid))
  		{
  			if (anycompatible_multirange_typelem !=
  				anycompatible_range_typeid)
  				return false;
  		}
  		else
  		{
  			anycompatible_range_typeid = anycompatible_multirange_typelem;
  			anycompatible_range_typelem = get_range_subtype(anycompatible_range_typeid);
  			if (!OidIsValid(anycompatible_range_typelem))
  				return false;	/* not a range type */
  			/* collect the subtype for common-supertype choice */
  			anycompatible_actual_types[n_anycompatible_args++] =
  				anycompatible_range_typelem;
  		}
  	}
  
  	/* Check matching of ANYCOMPATIBLE-family arguments, if any */
  	if (n_anycompatible_args > 0)
  	{
  		Oid			anycompatible_typeid;
  
  		anycompatible_typeid =
  			select_common_type_from_oids(n_anycompatible_args,
  										 anycompatible_actual_types,
  										 true);
  
  		if (!OidIsValid(anycompatible_typeid))
  			return false;		/* there's no common supertype */
  
  		if (have_anycompatible_nonarray)
  		{
  			/*
  			 * require the anycompatible type to not be an array or domain
  			 * over array
  			 */
  			if (type_is_array_domain(anycompatible_typeid))
  				return false;
  		}
  
  		/*
  		 * The anycompatible type must exactly match the range element type,
  		 * if we were able to identify one. This checks compatibility for
  		 * anycompatiblemultirange too since that also sets
  		 * anycompatible_range_typelem above.
  		 */
  		if (OidIsValid(anycompatible_range_typelem) &&
  			anycompatible_range_typelem != anycompatible_typeid)
  			return false;
  	}
  
  	/* Looks valid */
  	return true;
  }
  
  /*
   * enforce_generic_type_consistency()
   *		Make sure a polymorphic function is legally callable, and
   *		deduce actual argument and result types.
   *
   * If any polymorphic pseudotype is used in a function's arguments or
   * return type, we make sure the actual data types are consistent with
   * each other.  The argument consistency rules are shown above for
   * check_generic_type_consistency().
   *
   * If we have UNKNOWN input (ie, an untyped literal) for any polymorphic
   * argument, we attempt to deduce the actual type it should have.  If
   * successful, we alter that position of declared_arg_types[] so that
   * make_fn_arguments will coerce the literal to the right thing.
   *
   * If we have polymorphic arguments of the ANYCOMPATIBLE family,
   * we similarly alter declared_arg_types[] entries to show the resolved
   * common supertype, so that make_fn_arguments will coerce the actual
   * arguments to the proper type.
   *
   * Rules are applied to the function's return type (possibly altering it)
   * if it is declared as a polymorphic type and there is at least one
   * polymorphic argument type:
   *
   * 1) If return type is ANYELEMENT, and any argument is ANYELEMENT, use the
   *	  argument's actual type as the function's return type.
   * 2) If return type is ANYARRAY, and any argument is ANYARRAY, use the
   *	  argument's actual type as the function's return type.
   * 3) Similarly, if return type is ANYRANGE or ANYMULTIRANGE, and any
   *	  argument is ANYRANGE or ANYMULTIRANGE, use that argument's actual type
   *	  (or the corresponding range or multirange type) as the function's return
   *	  type.
   * 4) Otherwise, if return type is ANYELEMENT or ANYARRAY, and there is
   *	  at least one ANYELEMENT, ANYARRAY, ANYRANGE, or ANYMULTIRANGE input,
   *	  deduce the return type from those inputs, or throw error if we can't.
   * 5) Otherwise, if return type is ANYRANGE or ANYMULTIRANGE, throw error.
   *	  (We have no way to select a specific range type if the arguments don't
   *	  include ANYRANGE or ANYMULTIRANGE.)
   * 6) ANYENUM is treated the same as ANYELEMENT except that if it is used
   *	  (alone or in combination with plain ANYELEMENT), we add the extra
   *	  condition that the ANYELEMENT type must be an enum.
   * 7) ANYNONARRAY is treated the same as ANYELEMENT except that if it is used,
   *	  we add the extra condition that the ANYELEMENT type must not be an array.
   *	  (This is a no-op if used in combination with ANYARRAY or ANYENUM, but
   *	  is an extra restriction if not.)
   * 8) ANYCOMPATIBLE, ANYCOMPATIBLEARRAY, and ANYCOMPATIBLENONARRAY are handled
   *	  by resolving the common supertype of those arguments (or their element
   *	  types, for array inputs), and then coercing all those arguments to the
   *	  common supertype, or the array type over the common supertype for
   *	  ANYCOMPATIBLEARRAY.
   * 9) For ANYCOMPATIBLERANGE and ANYCOMPATIBLEMULTIRANGE, there must be at
   *	  least one non-UNKNOWN input matching those arguments, and all such
   *	  inputs must be the same range type (or its multirange type, as
   *	  appropriate), since we cannot deduce a range type from non-range types.
   *	  Furthermore, the range type's subtype is included while choosing the
   *	  common supertype for ANYCOMPATIBLE et al, and it must exactly match
   *	  that common supertype.
   *
   * Domains over arrays or ranges match ANYARRAY or ANYRANGE arguments,
   * respectively, and are immediately flattened to their base type.  (In
   * particular, if the return type is also ANYARRAY or ANYRANGE, we'll set
   * it to the base type not the domain type.)  The same is true for
   * ANYMULTIRANGE, ANYCOMPATIBLEARRAY, ANYCOMPATIBLERANGE, and
   * ANYCOMPATIBLEMULTIRANGE.
   *
   * When allow_poly is false, we are not expecting any of the actual_arg_types
   * to be polymorphic, and we should not return a polymorphic result type
   * either.  When allow_poly is true, it is okay to have polymorphic "actual"
   * arg types, and we can return a matching polymorphic type as the result.
   * (This case is currently used only to check compatibility of an aggregate's
   * declaration with the underlying transfn.)
   *
   * A special case is that we could see ANYARRAY as an actual_arg_type even
   * when allow_poly is false (this is possible only because pg_statistic has
   * columns shown as anyarray in the catalogs).  We allow this to match a
   * declared ANYARRAY argument, but only if there is no other polymorphic
   * argument that we would need to match it with, and no need to determine
   * the element type to infer the result type.  Note this means that functions
   * taking ANYARRAY had better behave sanely if applied to the pg_statistic
   * columns; they can't just assume that successive inputs are of the same
   * actual element type.  There is no similar logic for ANYCOMPATIBLEARRAY;
   * there isn't a need for it since there are no catalog columns of that type,
   * so we won't see it as input.  We could consider matching an actual ANYARRAY
   * input to an ANYCOMPATIBLEARRAY argument, but at present that seems useless
   * as well, since there's no value in using ANYCOMPATIBLEARRAY unless there's
   * at least one other ANYCOMPATIBLE-family argument or result.
   *
   * Also, if there are no arguments declared to be of polymorphic types,
   * we'll return the rettype unmodified even if it's polymorphic.  This should
   * never occur for user-declared functions, because CREATE FUNCTION prevents
   * it.  But it does happen for some built-in functions, such as array_in().
   */
  Oid
  enforce_generic_type_consistency(const Oid *actual_arg_types,
  								 Oid *declared_arg_types,
  								 int nargs,
  								 Oid rettype,
  								 bool allow_poly)
  {
  	bool		have_poly_anycompatible = false;
  	bool		have_poly_unknowns = false;
  	Oid			elem_typeid = InvalidOid;
  	Oid			array_typeid = InvalidOid;
  	Oid			range_typeid = InvalidOid;
  	Oid			multirange_typeid = InvalidOid;
  	Oid			anycompatible_typeid = InvalidOid;
  	Oid			anycompatible_array_typeid = InvalidOid;
  	Oid			anycompatible_range_typeid = InvalidOid;
  	Oid			anycompatible_range_typelem = InvalidOid;
  	Oid			anycompatible_multirange_typeid = InvalidOid;
  	Oid			anycompatible_multirange_typelem = InvalidOid;
  	bool		have_anynonarray = (rettype == ANYNONARRAYOID);
  	bool		have_anyenum = (rettype == ANYENUMOID);
  	bool		have_anymultirange = (rettype == ANYMULTIRANGEOID);
  	bool		have_anycompatible_nonarray = (rettype == ANYCOMPATIBLENONARRAYOID);
  	bool		have_anycompatible_array = (rettype == ANYCOMPATIBLEARRAYOID);
  	bool		have_anycompatible_range = (rettype == ANYCOMPATIBLERANGEOID);
  	bool		have_anycompatible_multirange = (rettype == ANYCOMPATIBLEMULTIRANGEOID);
  	int			n_poly_args = 0;	/* this counts all family-1 arguments */
  	int			n_anycompatible_args = 0;	/* this counts only non-unknowns */
  	Oid			anycompatible_actual_types[FUNC_MAX_ARGS];
  
  	/*
  	 * Loop through the arguments to see if we have any that are polymorphic.
  	 * If so, require the actual types to be consistent.
  	 */
  	Assert(nargs <= FUNC_MAX_ARGS);
  	for (int j = 0; j < nargs; j++)
  	{
  		Oid			decl_type = declared_arg_types[j];
  		Oid			actual_type = actual_arg_types[j];
  
  		if (decl_type == ANYELEMENTOID ||
  			decl_type == ANYNONARRAYOID ||
  			decl_type == ANYENUMOID)
  		{
  			n_poly_args++;
  			if (decl_type == ANYNONARRAYOID)
  				have_anynonarray = true;
  			else if (decl_type == ANYENUMOID)
  				have_anyenum = true;
  			if (actual_type == UNKNOWNOID)
  			{
  				have_poly_unknowns = true;
  				continue;
  			}
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			if (OidIsValid(elem_typeid) && actual_type != elem_typeid)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("arguments declared \"%s\" are not all alike", "anyelement"),
  						 errdetail("%s versus %s",
  								   format_type_be(elem_typeid),
  								   format_type_be(actual_type))));
  			elem_typeid = actual_type;
  		}
  		else if (decl_type == ANYARRAYOID)
  		{
  			n_poly_args++;
  			if (actual_type == UNKNOWNOID)
  			{
  				have_poly_unknowns = true;
  				continue;
  			}
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(array_typeid) && actual_type != array_typeid)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("arguments declared \"%s\" are not all alike", "anyarray"),
  						 errdetail("%s versus %s",
  								   format_type_be(array_typeid),
  								   format_type_be(actual_type))));
  			array_typeid = actual_type;
  		}
  		else if (decl_type == ANYRANGEOID)
  		{
  			n_poly_args++;
  			if (actual_type == UNKNOWNOID)
  			{
  				have_poly_unknowns = true;
  				continue;
  			}
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(range_typeid) && actual_type != range_typeid)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("arguments declared \"%s\" are not all alike", "anyrange"),
  						 errdetail("%s versus %s",
  								   format_type_be(range_typeid),
  								   format_type_be(actual_type))));
  			range_typeid = actual_type;
  		}
  		else if (decl_type == ANYMULTIRANGEOID)
  		{
  			n_poly_args++;
  			have_anymultirange = true;
  			if (actual_type == UNKNOWNOID)
  			{
  				have_poly_unknowns = true;
  				continue;
  			}
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(multirange_typeid) && actual_type != multirange_typeid)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("arguments declared \"%s\" are not all alike", "anymultirange"),
  						 errdetail("%s versus %s",
  								   format_type_be(multirange_typeid),
  								   format_type_be(actual_type))));
  			multirange_typeid = actual_type;
  		}
  		else if (decl_type == ANYCOMPATIBLEOID ||
  				 decl_type == ANYCOMPATIBLENONARRAYOID)
  		{
  			have_poly_anycompatible = true;
  			if (decl_type == ANYCOMPATIBLENONARRAYOID)
  				have_anycompatible_nonarray = true;
  			if (actual_type == UNKNOWNOID)
  				continue;
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			/* collect the actual types of non-unknown COMPATIBLE args */
  			anycompatible_actual_types[n_anycompatible_args++] = actual_type;
  		}
  		else if (decl_type == ANYCOMPATIBLEARRAYOID)
  		{
  			Oid			anycompatible_elem_type;
  
  			have_poly_anycompatible = true;
  			have_anycompatible_array = true;
  			if (actual_type == UNKNOWNOID)
  				continue;
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			anycompatible_elem_type = get_element_type(actual_type);
  			if (!OidIsValid(anycompatible_elem_type))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument declared %s is not an array but type %s",
  								"anycompatiblearray",
  								format_type_be(actual_type))));
  			/* collect the element type for common-supertype choice */
  			anycompatible_actual_types[n_anycompatible_args++] = anycompatible_elem_type;
  		}
  		else if (decl_type == ANYCOMPATIBLERANGEOID)
  		{
  			have_poly_anycompatible = true;
  			have_anycompatible_range = true;
  			if (actual_type == UNKNOWNOID)
  				continue;
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(anycompatible_range_typeid))
  			{
  				/* All ANYCOMPATIBLERANGE arguments must be the same type */
  				if (anycompatible_range_typeid != actual_type)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("arguments declared \"%s\" are not all alike", "anycompatiblerange"),
  							 errdetail("%s versus %s",
  									   format_type_be(anycompatible_range_typeid),
  									   format_type_be(actual_type))));
  			}
  			else
  			{
  				anycompatible_range_typeid = actual_type;
  				anycompatible_range_typelem = get_range_subtype(actual_type);
  				if (!OidIsValid(anycompatible_range_typelem))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("argument declared %s is not a range type but type %s",
  									"anycompatiblerange",
  									format_type_be(actual_type))));
  				/* collect the subtype for common-supertype choice */
  				anycompatible_actual_types[n_anycompatible_args++] = anycompatible_range_typelem;
  			}
  		}
  		else if (decl_type == ANYCOMPATIBLEMULTIRANGEOID)
  		{
  			have_poly_anycompatible = true;
  			have_anycompatible_multirange = true;
  			if (actual_type == UNKNOWNOID)
  				continue;
  			if (allow_poly && decl_type == actual_type)
  				continue;		/* no new information here */
  			actual_type = getBaseType(actual_type); /* flatten domains */
  			if (OidIsValid(anycompatible_multirange_typeid))
  			{
  				/* All ANYCOMPATIBLEMULTIRANGE arguments must be the same type */
  				if (anycompatible_multirange_typeid != actual_type)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("arguments declared \"%s\" are not all alike", "anycompatiblemultirange"),
  							 errdetail("%s versus %s",
  									   format_type_be(anycompatible_multirange_typeid),
  									   format_type_be(actual_type))));
  			}
  			else
  			{
  				anycompatible_multirange_typeid = actual_type;
  				anycompatible_multirange_typelem = get_multirange_range(actual_type);
  				if (!OidIsValid(anycompatible_multirange_typelem))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("argument declared %s is not a multirange type but type %s",
  									"anycompatiblemultirange",
  									format_type_be(actual_type))));
  				/* we'll consider the subtype below */
  			}
  		}
  	}
  
  	/*
  	 * Fast Track: if none of the arguments are polymorphic, return the
  	 * unmodified rettype.  Not our job to resolve it if it's polymorphic.
  	 */
  	if (n_poly_args == 0 && !have_poly_anycompatible)
  		return rettype;
  
  	/* Check matching of family-1 polymorphic arguments, if any */
  	if (n_poly_args)
  	{
  		/* Get the element type based on the array type, if we have one */
  		if (OidIsValid(array_typeid))
  		{
  			Oid			array_typelem;
  
  			if (array_typeid == ANYARRAYOID)
  			{
  				/*
  				 * Special case for matching ANYARRAY input to an ANYARRAY
  				 * argument: allow it iff no other arguments are family-1
  				 * polymorphics (otherwise we couldn't be sure whether the
  				 * array element type matches up) and the result type doesn't
  				 * require us to infer a specific element type.
  				 */
  				if (n_poly_args != 1 ||
  					(rettype != ANYARRAYOID &&
  					 IsPolymorphicTypeFamily1(rettype)))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("cannot determine element type of \"anyarray\" argument")));
  				array_typelem = ANYELEMENTOID;
  			}
  			else
  			{
  				array_typelem = get_element_type(array_typeid);
  				if (!OidIsValid(array_typelem))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("argument declared %s is not an array but type %s",
  									"anyarray", format_type_be(array_typeid))));
  			}
  
  			if (!OidIsValid(elem_typeid))
  			{
  				/*
  				 * if we don't have an element type yet, use the one we just
  				 * got
  				 */
  				elem_typeid = array_typelem;
  			}
  			else if (array_typelem != elem_typeid)
  			{
  				/* otherwise, they better match */
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument declared %s is not consistent with argument declared %s",
  								"anyarray", "anyelement"),
  						 errdetail("%s versus %s",
  								   format_type_be(array_typeid),
  								   format_type_be(elem_typeid))));
  			}
  		}
  
  		/* Deduce range type from multirange type, or vice versa */
  		if (OidIsValid(multirange_typeid))
  		{
  			Oid			multirange_typelem;
  
  			multirange_typelem = get_multirange_range(multirange_typeid);
  			if (!OidIsValid(multirange_typelem))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument declared %s is not a multirange type but type %s",
  								"anymultirange",
  								format_type_be(multirange_typeid))));
  
  			if (!OidIsValid(range_typeid))
  			{
  				/* if we don't have a range type yet, use the one we just got */
  				range_typeid = multirange_typelem;
  			}
  			else if (multirange_typelem != range_typeid)
  			{
  				/* otherwise, they better match */
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument declared %s is not consistent with argument declared %s",
  								"anymultirange", "anyrange"),
  						 errdetail("%s versus %s",
  								   format_type_be(multirange_typeid),
  								   format_type_be(range_typeid))));
  			}
  		}
  		else if (have_anymultirange && OidIsValid(range_typeid))
  		{
  			multirange_typeid = get_range_multirange(range_typeid);
  			/* We'll complain below if that didn't work */
  		}
  
  		/* Get the element type based on the range type, if we have one */
  		if (OidIsValid(range_typeid))
  		{
  			Oid			range_typelem;
  
  			range_typelem = get_range_subtype(range_typeid);
  			if (!OidIsValid(range_typelem))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument declared %s is not a range type but type %s",
  								"anyrange",
  								format_type_be(range_typeid))));
  
  			if (!OidIsValid(elem_typeid))
  			{
  				/*
  				 * if we don't have an element type yet, use the one we just
  				 * got
  				 */
  				elem_typeid = range_typelem;
  			}
  			else if (range_typelem != elem_typeid)
  			{
  				/* otherwise, they better match */
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("argument declared %s is not consistent with argument declared %s",
  								"anyrange", "anyelement"),
  						 errdetail("%s versus %s",
  								   format_type_be(range_typeid),
  								   format_type_be(elem_typeid))));
  			}
  		}
  
  		if (!OidIsValid(elem_typeid))
  		{
  			if (allow_poly)
  			{
  				elem_typeid = ANYELEMENTOID;
  				array_typeid = ANYARRAYOID;
  				range_typeid = ANYRANGEOID;
  				multirange_typeid = ANYMULTIRANGEOID;
  			}
  			else
  			{
  				/*
  				 * Only way to get here is if all the family-1 polymorphic
  				 * arguments have UNKNOWN inputs.
  				 */
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("could not determine polymorphic type because input has type %s",
  								"unknown")));
  			}
  		}
  
  		if (have_anynonarray && elem_typeid != ANYELEMENTOID)
  		{
  			/*
  			 * require the element type to not be an array or domain over
  			 * array
  			 */
  			if (type_is_array_domain(elem_typeid))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("type matched to anynonarray is an array type: %s",
  								format_type_be(elem_typeid))));
  		}
  
  		if (have_anyenum && elem_typeid != ANYELEMENTOID)
  		{
  			/* require the element type to be an enum */
  			if (!type_is_enum(elem_typeid))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("type matched to anyenum is not an enum type: %s",
  								format_type_be(elem_typeid))));
  		}
  	}
  
  	/* Check matching of family-2 polymorphic arguments, if any */
  	if (have_poly_anycompatible)
  	{
  		/* Deduce range type from multirange type, or vice versa */
  		if (OidIsValid(anycompatible_multirange_typeid))
  		{
  			if (OidIsValid(anycompatible_range_typeid))
  			{
  				if (anycompatible_multirange_typelem !=
  					anycompatible_range_typeid)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("argument declared %s is not consistent with argument declared %s",
  									"anycompatiblemultirange",
  									"anycompatiblerange"),
  							 errdetail("%s versus %s",
  									   format_type_be(anycompatible_multirange_typeid),
  									   format_type_be(anycompatible_range_typeid))));
  			}
  			else
  			{
  				anycompatible_range_typeid = anycompatible_multirange_typelem;
  				anycompatible_range_typelem = get_range_subtype(anycompatible_range_typeid);
  				if (!OidIsValid(anycompatible_range_typelem))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("argument declared %s is not a multirange type but type %s",
  									"anycompatiblemultirange",
  									format_type_be(anycompatible_multirange_typeid))));
  				/* this enables element type matching check below */
  				have_anycompatible_range = true;
  				/* collect the subtype for common-supertype choice */
  				anycompatible_actual_types[n_anycompatible_args++] =
  					anycompatible_range_typelem;
  			}
  		}
  		else if (have_anycompatible_multirange &&
  				 OidIsValid(anycompatible_range_typeid))
  		{
  			anycompatible_multirange_typeid = get_range_multirange(anycompatible_range_typeid);
  			/* We'll complain below if that didn't work */
  		}
  
  		if (n_anycompatible_args > 0)
  		{
  			anycompatible_typeid =
  				select_common_type_from_oids(n_anycompatible_args,
  											 anycompatible_actual_types,
  											 false);
  
  			if (have_anycompatible_array)
  			{
  				anycompatible_array_typeid = get_array_type(anycompatible_typeid);
  				if (!OidIsValid(anycompatible_array_typeid))
  					ereport(ERROR,
  							(errcode(ERRCODE_UNDEFINED_OBJECT),
  							 errmsg("could not find array type for data type %s",
  									format_type_be(anycompatible_typeid))));
  			}
  
  			if (have_anycompatible_range)
  			{
  				/* we can't infer a range type from the others */
  				if (!OidIsValid(anycompatible_range_typeid))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine polymorphic type %s because input has type %s",
  									"anycompatiblerange", "unknown")));
  
  				/*
  				 * the anycompatible type must exactly match the range element
  				 * type
  				 */
  				if (anycompatible_range_typelem != anycompatible_typeid)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("anycompatiblerange type %s does not match anycompatible type %s",
  									format_type_be(anycompatible_range_typeid),
  									format_type_be(anycompatible_typeid))));
  			}
  
  			if (have_anycompatible_multirange)
  			{
  				/* we can't infer a multirange type from the others */
  				if (!OidIsValid(anycompatible_multirange_typeid))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine polymorphic type %s because input has type %s",
  									"anycompatiblemultirange", "unknown")));
  
  				/*
  				 * the anycompatible type must exactly match the multirange
  				 * element type
  				 */
  				if (anycompatible_range_typelem != anycompatible_typeid)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("anycompatiblemultirange type %s does not match anycompatible type %s",
  									format_type_be(anycompatible_multirange_typeid),
  									format_type_be(anycompatible_typeid))));
  			}
  
  			if (have_anycompatible_nonarray)
  			{
  				/*
  				 * require the element type to not be an array or domain over
  				 * array
  				 */
  				if (type_is_array_domain(anycompatible_typeid))
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("type matched to anycompatiblenonarray is an array type: %s",
  									format_type_be(anycompatible_typeid))));
  			}
  		}
  		else
  		{
  			if (allow_poly)
  			{
  				anycompatible_typeid = ANYCOMPATIBLEOID;
  				anycompatible_array_typeid = ANYCOMPATIBLEARRAYOID;
  				anycompatible_range_typeid = ANYCOMPATIBLERANGEOID;
  				anycompatible_multirange_typeid = ANYCOMPATIBLEMULTIRANGEOID;
  			}
  			else
  			{
  				/*
  				 * Only way to get here is if all the family-2 polymorphic
  				 * arguments have UNKNOWN inputs.  Resolve to TEXT as
  				 * select_common_type() would do.  That doesn't license us to
  				 * use TEXTRANGE or TEXTMULTIRANGE, though.
  				 */
  				anycompatible_typeid = TEXTOID;
  				anycompatible_array_typeid = TEXTARRAYOID;
  				if (have_anycompatible_range)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine polymorphic type %s because input has type %s",
  									"anycompatiblerange", "unknown")));
  				if (have_anycompatible_multirange)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine polymorphic type %s because input has type %s",
  									"anycompatiblemultirange", "unknown")));
  			}
  		}
  
  		/* replace family-2 polymorphic types by selected types */
  		for (int j = 0; j < nargs; j++)
  		{
  			Oid			decl_type = declared_arg_types[j];
  
  			if (decl_type == ANYCOMPATIBLEOID ||
  				decl_type == ANYCOMPATIBLENONARRAYOID)
  				declared_arg_types[j] = anycompatible_typeid;
  			else if (decl_type == ANYCOMPATIBLEARRAYOID)
  				declared_arg_types[j] = anycompatible_array_typeid;
  			else if (decl_type == ANYCOMPATIBLERANGEOID)
  				declared_arg_types[j] = anycompatible_range_typeid;
  			else if (decl_type == ANYCOMPATIBLEMULTIRANGEOID)
  				declared_arg_types[j] = anycompatible_multirange_typeid;
  		}
  	}
  
  	/*
  	 * If we had any UNKNOWN inputs for family-1 polymorphic arguments,
  	 * re-scan to assign correct types to them.
  	 *
  	 * Note: we don't have to consider unknown inputs that were matched to
  	 * family-2 polymorphic arguments, because we forcibly updated their
  	 * declared_arg_types[] positions just above.
  	 */
  	if (have_poly_unknowns)
  	{
  		for (int j = 0; j < nargs; j++)
  		{
  			Oid			decl_type = declared_arg_types[j];
  			Oid			actual_type = actual_arg_types[j];
  
  			if (actual_type != UNKNOWNOID)
  				continue;
  
  			if (decl_type == ANYELEMENTOID ||
  				decl_type == ANYNONARRAYOID ||
  				decl_type == ANYENUMOID)
  				declared_arg_types[j] = elem_typeid;
  			else if (decl_type == ANYARRAYOID)
  			{
  				if (!OidIsValid(array_typeid))
  				{
  					array_typeid = get_array_type(elem_typeid);
  					if (!OidIsValid(array_typeid))
  						ereport(ERROR,
  								(errcode(ERRCODE_UNDEFINED_OBJECT),
  								 errmsg("could not find array type for data type %s",
  										format_type_be(elem_typeid))));
  				}
  				declared_arg_types[j] = array_typeid;
  			}
  			else if (decl_type == ANYRANGEOID)
  			{
  				if (!OidIsValid(range_typeid))
  				{
  					/* we can't infer a range type from the others */
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine polymorphic type %s because input has type %s",
  									"anyrange", "unknown")));
  				}
  				declared_arg_types[j] = range_typeid;
  			}
  			else if (decl_type == ANYMULTIRANGEOID)
  			{
  				if (!OidIsValid(multirange_typeid))
  				{
  					/* we can't infer a multirange type from the others */
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine polymorphic type %s because input has type %s",
  									"anymultirange", "unknown")));
  				}
  				declared_arg_types[j] = multirange_typeid;
  			}
  		}
  	}
  
  	/* if we return ANYELEMENT use the appropriate argument type */
  	if (rettype == ANYELEMENTOID ||
  		rettype == ANYNONARRAYOID ||
  		rettype == ANYENUMOID)
  		return elem_typeid;
  
  	/* if we return ANYARRAY use the appropriate argument type */
  	if (rettype == ANYARRAYOID)
  	{
  		if (!OidIsValid(array_typeid))
  		{
  			array_typeid = get_array_type(elem_typeid);
  			if (!OidIsValid(array_typeid))
  				ereport(ERROR,
  						(errcode(ERRCODE_UNDEFINED_OBJECT),
  						 errmsg("could not find array type for data type %s",
  								format_type_be(elem_typeid))));
  		}
  		return array_typeid;
  	}
  
  	/* if we return ANYRANGE use the appropriate argument type */
  	if (rettype == ANYRANGEOID)
  	{
  		/* this error is unreachable if the function signature is valid: */
  		if (!OidIsValid(range_typeid))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg_internal("could not determine polymorphic type %s because input has type %s",
  									 "anyrange", "unknown")));
  		return range_typeid;
  	}
  
  	/* if we return ANYMULTIRANGE use the appropriate argument type */
  	if (rettype == ANYMULTIRANGEOID)
  	{
  		/* this error is unreachable if the function signature is valid: */
  		if (!OidIsValid(multirange_typeid))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg_internal("could not determine polymorphic type %s because input has type %s",
  									 "anymultirange", "unknown")));
  		return multirange_typeid;
  	}
  
  	/* if we return ANYCOMPATIBLE use the appropriate type */
  	if (rettype == ANYCOMPATIBLEOID ||
  		rettype == ANYCOMPATIBLENONARRAYOID)
  	{
  		/* this error is unreachable if the function signature is valid: */
  		if (!OidIsValid(anycompatible_typeid))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg_internal("could not identify anycompatible type")));
  		return anycompatible_typeid;
  	}
  
  	/* if we return ANYCOMPATIBLEARRAY use the appropriate type */
  	if (rettype == ANYCOMPATIBLEARRAYOID)
  	{
  		/* this error is unreachable if the function signature is valid: */
  		if (!OidIsValid(anycompatible_array_typeid))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg_internal("could not identify anycompatiblearray type")));
  		return anycompatible_array_typeid;
  	}
  
  	/* if we return ANYCOMPATIBLERANGE use the appropriate argument type */
  	if (rettype == ANYCOMPATIBLERANGEOID)
  	{
  		/* this error is unreachable if the function signature is valid: */
  		if (!OidIsValid(anycompatible_range_typeid))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg_internal("could not identify anycompatiblerange type")));
  		return anycompatible_range_typeid;
  	}
  
  	/* if we return ANYCOMPATIBLEMULTIRANGE use the appropriate argument type */
  	if (rettype == ANYCOMPATIBLEMULTIRANGEOID)
  	{
  		/* this error is unreachable if the function signature is valid: */
  		if (!OidIsValid(anycompatible_multirange_typeid))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg_internal("could not identify anycompatiblemultirange type")));
  		return anycompatible_multirange_typeid;
  	}
  
  	/* we don't return a generic type; send back the original return type */
  	return rettype;
  }
  
  /*
   * check_valid_polymorphic_signature()
   *		Is a proposed function signature valid per polymorphism rules?
   *
   * Returns NULL if the signature is valid (either ret_type is not polymorphic,
   * or it can be deduced from the given declared argument types).  Otherwise,
   * returns a palloc'd, already translated errdetail string saying why not.
   */
  char *
  check_valid_polymorphic_signature(Oid ret_type,
  								  const Oid *declared_arg_types,
  								  int nargs)
  {
  	if (ret_type == ANYRANGEOID || ret_type == ANYMULTIRANGEOID)
  	{
  		/*
  		 * ANYRANGE and ANYMULTIRANGE require an ANYRANGE or ANYMULTIRANGE
  		 * input, else we can't tell which of several range types with the
  		 * same element type to use.
  		 */
  		for (int i = 0; i < nargs; i++)
  		{
  			if (declared_arg_types[i] == ANYRANGEOID ||
  				declared_arg_types[i] == ANYMULTIRANGEOID)
  				return NULL;	/* OK */
  		}
  		return psprintf(_("A result of type %s requires at least one input of type anyrange or anymultirange."),
  						format_type_be(ret_type));
  	}
  	else if (ret_type == ANYCOMPATIBLERANGEOID || ret_type == ANYCOMPATIBLEMULTIRANGEOID)
  	{
  		/*
  		 * ANYCOMPATIBLERANGE and ANYCOMPATIBLEMULTIRANGE require an
  		 * ANYCOMPATIBLERANGE or ANYCOMPATIBLEMULTIRANGE input, else we can't
  		 * tell which of several range types with the same element type to
  		 * use.
  		 */
  		for (int i = 0; i < nargs; i++)
  		{
  			if (declared_arg_types[i] == ANYCOMPATIBLERANGEOID ||
  				declared_arg_types[i] == ANYCOMPATIBLEMULTIRANGEOID)
  				return NULL;	/* OK */
  		}
  		return psprintf(_("A result of type %s requires at least one input of type anycompatiblerange or anycompatiblemultirange."),
  						format_type_be(ret_type));
  	}
  	else if (IsPolymorphicTypeFamily1(ret_type))
  	{
  		/* Otherwise, any family-1 type can be deduced from any other */
  		for (int i = 0; i < nargs; i++)
  		{
  			if (IsPolymorphicTypeFamily1(declared_arg_types[i]))
  				return NULL;	/* OK */
  		}
  		/* Keep this list in sync with IsPolymorphicTypeFamily1! */
  		return psprintf(_("A result of type %s requires at least one input of type anyelement, anyarray, anynonarray, anyenum, anyrange, or anymultirange."),
  						format_type_be(ret_type));
  	}
  	else if (IsPolymorphicTypeFamily2(ret_type))
  	{
  		/* Otherwise, any family-2 type can be deduced from any other */
  		for (int i = 0; i < nargs; i++)
  		{
  			if (IsPolymorphicTypeFamily2(declared_arg_types[i]))
  				return NULL;	/* OK */
  		}
  		/* Keep this list in sync with IsPolymorphicTypeFamily2! */
  		return psprintf(_("A result of type %s requires at least one input of type anycompatible, anycompatiblearray, anycompatiblenonarray, anycompatiblerange, or anycompatiblemultirange."),
  						format_type_be(ret_type));
  	}
  	else
  		return NULL;			/* OK, ret_type is not polymorphic */
  }
  
  /*
   * check_valid_internal_signature()
   *		Is a proposed function signature valid per INTERNAL safety rules?
   *
   * Returns NULL if OK, or a suitable error message if ret_type is INTERNAL but
   * none of the declared arg types are.  (It's unsafe to create such a function
   * since it would allow invocation of INTERNAL-consuming functions directly
   * from SQL.)  It's overkill to return the error detail message, since there
   * is only one possibility, but we do it like this to keep the API similar to
   * check_valid_polymorphic_signature().
   */
  char *
  check_valid_internal_signature(Oid ret_type,
  							   const Oid *declared_arg_types,
  							   int nargs)
  {
  	if (ret_type == INTERNALOID)
  	{
  		for (int i = 0; i < nargs; i++)
  		{
  			if (declared_arg_types[i] == ret_type)
  				return NULL;	/* OK */
  		}
  		return pstrdup(_("A result of type internal requires at least one input of type internal."));
  	}
  	else
  		return NULL;			/* OK, ret_type is not INTERNAL */
  }
  
  
  /* TypeCategory()
   *		Assign a category to the specified type OID.
   *
   * NB: this must not return TYPCATEGORY_INVALID.
   */
  TYPCATEGORY
  TypeCategory(Oid type)
  {
  	char		typcategory;
  	bool		typispreferred;
  
  	get_type_category_preferred(type, &typcategory, &typispreferred);
  	Assert(typcategory != TYPCATEGORY_INVALID);
  	return (TYPCATEGORY) typcategory;
  }
  
  
  /* IsPreferredType()
   *		Check if this type is a preferred type for the given category.
   *
   * If category is TYPCATEGORY_INVALID, then we'll return true for preferred
   * types of any category; otherwise, only for preferred types of that
   * category.
   */
  bool
  IsPreferredType(TYPCATEGORY category, Oid type)
  {
  	char		typcategory;
  	bool		typispreferred;
  
  	get_type_category_preferred(type, &typcategory, &typispreferred);
  	if (category == typcategory || category == TYPCATEGORY_INVALID)
  		return typispreferred;
  	else
  		return false;
  }
  
  
  /* IsBinaryCoercible()
   *		Check if srctype is binary-coercible to targettype.
   *
   * This notion allows us to cheat and directly exchange values without
   * going through the trouble of calling a conversion function.  Note that
   * in general, this should only be an implementation shortcut.  Before 7.4,
   * this was also used as a heuristic for resolving overloaded functions and
   * operators, but that's basically a bad idea.
   *
   * As of 7.3, binary coercibility isn't hardwired into the code anymore.
   * We consider two types binary-coercible if there is an implicitly
   * invokable, no-function-needed pg_cast entry.  Also, a domain is always
   * binary-coercible to its base type, though *not* vice versa (in the other
   * direction, one must apply domain constraint checks before accepting the
   * value as legitimate).  We also need to special-case various polymorphic
   * types.
   *
   * This function replaces IsBinaryCompatible(), which was an inherently
   * symmetric test.  Since the pg_cast entries aren't necessarily symmetric,
   * the order of the operands is now significant.
   */
  bool
  IsBinaryCoercible(Oid srctype, Oid targettype)
  {
  	HeapTuple	tuple;
  	Form_pg_cast castForm;
  	bool		result;
  
  	/* Fast path if same type */
  	if (srctype == targettype)
  		return true;
  
  	/* Anything is coercible to ANY or ANYELEMENT or ANYCOMPATIBLE */
  	if (targettype == ANYOID || targettype == ANYELEMENTOID ||
  		targettype == ANYCOMPATIBLEOID)
  		return true;
  
  	/* If srctype is a domain, reduce to its base type */
  	if (OidIsValid(srctype))
  		srctype = getBaseType(srctype);
  
  	/* Somewhat-fast path for domain -> base type case */
  	if (srctype == targettype)
  		return true;
  
  	/* Also accept any array type as coercible to ANY[COMPATIBLE]ARRAY */
  	if (targettype == ANYARRAYOID || targettype == ANYCOMPATIBLEARRAYOID)
  		if (type_is_array(srctype))
  			return true;
  
  	/* Also accept any non-array type as coercible to ANY[COMPATIBLE]NONARRAY */
  	if (targettype == ANYNONARRAYOID || targettype == ANYCOMPATIBLENONARRAYOID)
  		if (!type_is_array(srctype))
  			return true;
  
  	/* Also accept any enum type as coercible to ANYENUM */
  	if (targettype == ANYENUMOID)
  		if (type_is_enum(srctype))
  			return true;
  
  	/* Also accept any range type as coercible to ANY[COMPATIBLE]RANGE */
  	if (targettype == ANYRANGEOID || targettype == ANYCOMPATIBLERANGEOID)
  		if (type_is_range(srctype))
  			return true;
  
  	/* Also, any multirange type is coercible to ANY[COMPATIBLE]MULTIRANGE */
  	if (targettype == ANYMULTIRANGEOID || targettype == ANYCOMPATIBLEMULTIRANGEOID)
  		if (type_is_multirange(srctype))
  			return true;
  
  	/* Also accept any composite type as coercible to RECORD */
  	if (targettype == RECORDOID)
  		if (ISCOMPLEX(srctype))
  			return true;
  
  	/* Also accept any composite array type as coercible to RECORD[] */
  	if (targettype == RECORDARRAYOID)
  		if (is_complex_array(srctype))
  			return true;
  
  	/* Else look in pg_cast */
  	tuple = SearchSysCache2(CASTSOURCETARGET,
  							ObjectIdGetDatum(srctype),
  							ObjectIdGetDatum(targettype));
  	if (!HeapTupleIsValid(tuple))
  		return false;			/* no cast */
  	castForm = (Form_pg_cast) GETSTRUCT(tuple);
  
  	result = (castForm->castmethod == COERCION_METHOD_BINARY &&
  			  castForm->castcontext == COERCION_CODE_IMPLICIT);
  
  	ReleaseSysCache(tuple);
  
  	return result;
  }
  
  
  /*
   * find_coercion_pathway
   *		Look for a coercion pathway between two types.
   *
   * Currently, this deals only with scalar-type cases; it does not consider
   * polymorphic types nor casts between composite types.  (Perhaps fold
   * those in someday?)
   *
   * ccontext determines the set of available casts.
   *
   * The possible result codes are:
   *	COERCION_PATH_NONE: failed to find any coercion pathway
   *				*funcid is set to InvalidOid
   *	COERCION_PATH_FUNC: apply the coercion function returned in *funcid
   *	COERCION_PATH_RELABELTYPE: binary-compatible cast, no function needed
   *				*funcid is set to InvalidOid
   *	COERCION_PATH_ARRAYCOERCE: need an ArrayCoerceExpr node
   *				*funcid is set to InvalidOid
   *	COERCION_PATH_COERCEVIAIO: need a CoerceViaIO node
   *				*funcid is set to InvalidOid
   *
   * Note: COERCION_PATH_RELABELTYPE does not necessarily mean that no work is
   * needed to do the coercion; if the target is a domain then we may need to
   * apply domain constraint checking.  If you want to check for a zero-effort
   * conversion then use IsBinaryCoercible().
   */
  CoercionPathType
  find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
  					  CoercionContext ccontext,
  					  Oid *funcid)
  {
  	CoercionPathType result = COERCION_PATH_NONE;
  	HeapTuple	tuple;
  
  	*funcid = InvalidOid;
  
  	/* Perhaps the types are domains; if so, look at their base types */
  	if (OidIsValid(sourceTypeId))
  		sourceTypeId = getBaseType(sourceTypeId);
  	if (OidIsValid(targetTypeId))
  		targetTypeId = getBaseType(targetTypeId);
  
  	/* Domains are always coercible to and from their base type */
  	if (sourceTypeId == targetTypeId)
  		return COERCION_PATH_RELABELTYPE;
  
  	/* Look in pg_cast */
  	tuple = SearchSysCache2(CASTSOURCETARGET,
  							ObjectIdGetDatum(sourceTypeId),
  							ObjectIdGetDatum(targetTypeId));
  
  	if (HeapTupleIsValid(tuple))
  	{
  		Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
  		CoercionContext castcontext;
  
  		/* convert char value for castcontext to CoercionContext enum */
  		switch (castForm->castcontext)
  		{
  			case COERCION_CODE_IMPLICIT:
  				castcontext = COERCION_IMPLICIT;
  				break;
  			case COERCION_CODE_ASSIGNMENT:
  				castcontext = COERCION_ASSIGNMENT;
  				break;
  			case COERCION_CODE_EXPLICIT:
  				castcontext = COERCION_EXPLICIT;
  				break;
  			default:
  				elog(ERROR, "unrecognized castcontext: %d",
  					 (int) castForm->castcontext);
  				castcontext = 0;	/* keep compiler quiet */
  				break;
  		}
  
  		/* Rely on ordering of enum for correct behavior here */
  		if (ccontext >= castcontext)
  		{
  			switch (castForm->castmethod)
  			{
  				case COERCION_METHOD_FUNCTION:
  					result = COERCION_PATH_FUNC;
  					*funcid = castForm->castfunc;
  					break;
  				case COERCION_METHOD_INOUT:
  					result = COERCION_PATH_COERCEVIAIO;
  					break;
  				case COERCION_METHOD_BINARY:
  					result = COERCION_PATH_RELABELTYPE;
  					break;
  				default:
  					elog(ERROR, "unrecognized castmethod: %d",
  						 (int) castForm->castmethod);
  					break;
  			}
  		}
  
  		ReleaseSysCache(tuple);
  	}
  	else
  	{
  		/*
  		 * If there's no pg_cast entry, perhaps we are dealing with a pair of
  		 * array types.  If so, and if their element types have a conversion
  		 * pathway, report that we can coerce with an ArrayCoerceExpr.
  		 *
  		 * Hack: disallow coercions to oidvector and int2vector, which
  		 * otherwise tend to capture coercions that should go to "real" array
  		 * types.  We want those types to be considered "real" arrays for many
  		 * purposes, but not this one.  (Also, ArrayCoerceExpr isn't
  		 * guaranteed to produce an output that meets the restrictions of
  		 * these datatypes, such as being 1-dimensional.)
  		 */
  		if (targetTypeId != OIDVECTOROID && targetTypeId != INT2VECTOROID)
  		{
  			Oid			targetElem;
  			Oid			sourceElem;
  
  			if ((targetElem = get_element_type(targetTypeId)) != InvalidOid &&
  				(sourceElem = get_element_type(sourceTypeId)) != InvalidOid)
  			{
  				CoercionPathType elempathtype;
  				Oid			elemfuncid;
  
  				elempathtype = find_coercion_pathway(targetElem,
  													 sourceElem,
  													 ccontext,
  													 &elemfuncid);
  				if (elempathtype != COERCION_PATH_NONE)
  				{
  					result = COERCION_PATH_ARRAYCOERCE;
  				}
  			}
  		}
  
  		/*
  		 * If we still haven't found a possibility, consider automatic casting
  		 * using I/O functions.  We allow assignment casts to string types and
  		 * explicit casts from string types to be handled this way. (The
  		 * CoerceViaIO mechanism is a lot more general than that, but this is
  		 * all we want to allow in the absence of a pg_cast entry.) It would
  		 * probably be better to insist on explicit casts in both directions,
  		 * but this is a compromise to preserve something of the pre-8.3
  		 * behavior that many types had implicit (yipes!) casts to text.
  		 */
  		if (result == COERCION_PATH_NONE)
  		{
  			if (ccontext >= COERCION_ASSIGNMENT &&
  				TypeCategory(targetTypeId) == TYPCATEGORY_STRING)
  				result = COERCION_PATH_COERCEVIAIO;
  			else if (ccontext >= COERCION_EXPLICIT &&
  					 TypeCategory(sourceTypeId) == TYPCATEGORY_STRING)
  				result = COERCION_PATH_COERCEVIAIO;
  		}
  	}
  
  	/*
  	 * When parsing PL/pgSQL assignments, allow an I/O cast to be used
  	 * whenever no normal coercion is available.
  	 */
  	if (result == COERCION_PATH_NONE &&
  		ccontext == COERCION_PLPGSQL)
  		result = COERCION_PATH_COERCEVIAIO;
  
  	return result;
  }
  
  
  /*
   * find_typmod_coercion_function -- does the given type need length coercion?
   *
   * If the target type possesses a pg_cast function from itself to itself,
   * it must need length coercion.
   *
   * "bpchar" (ie, char(N)) and "numeric" are examples of such types.
   *
   * If the given type is a varlena array type, we do not look for a coercion
   * function associated directly with the array type, but instead look for
   * one associated with the element type.  An ArrayCoerceExpr node must be
   * used to apply such a function.  (Note: currently, it's pointless to
   * return the funcid in this case, because it'll just get looked up again
   * in the recursive construction of the ArrayCoerceExpr's elemexpr.)
   *
   * We use the same result enum as find_coercion_pathway, but the only possible
   * result codes are:
   *	COERCION_PATH_NONE: no length coercion needed
   *	COERCION_PATH_FUNC: apply the function returned in *funcid
   *	COERCION_PATH_ARRAYCOERCE: apply the function using ArrayCoerceExpr
   */
  CoercionPathType
  find_typmod_coercion_function(Oid typeId,
  							  Oid *funcid)
  {
  	CoercionPathType result;
  	Type		targetType;
  	Form_pg_type typeForm;
  	HeapTuple	tuple;
  
  	*funcid = InvalidOid;
  	result = COERCION_PATH_FUNC;
  
  	targetType = typeidType(typeId);
  	typeForm = (Form_pg_type) GETSTRUCT(targetType);
  
  	/* Check for a "true" array type */
  	if (IsTrueArrayType(typeForm))
  	{
  		/* Yes, switch our attention to the element type */
  		typeId = typeForm->typelem;
  		result = COERCION_PATH_ARRAYCOERCE;
  	}
  	ReleaseSysCache(targetType);
  
  	/* Look in pg_cast */
  	tuple = SearchSysCache2(CASTSOURCETARGET,
  							ObjectIdGetDatum(typeId),
  							ObjectIdGetDatum(typeId));
  
  	if (HeapTupleIsValid(tuple))
  	{
  		Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
  
  		*funcid = castForm->castfunc;
  		ReleaseSysCache(tuple);
  	}
  
  	if (!OidIsValid(*funcid))
  		result = COERCION_PATH_NONE;
  
  	return result;
  }
  
  /*
   * is_complex_array
   *		Is this type an array of composite?
   *
   * Note: this will not return true for record[]; check for RECORDARRAYOID
   * separately if needed.
   */
  static bool
  is_complex_array(Oid typid)
  {
  	Oid			elemtype = get_element_type(typid);
  
  	return (OidIsValid(elemtype) && ISCOMPLEX(elemtype));
  }
  
  
  /*
   * Check whether reltypeId is the row type of a typed table of type
   * reloftypeId, or is a domain over such a row type.  (This is conceptually
   * similar to the subtype relationship checked by typeInheritsFrom().)
   */
  static bool
  typeIsOfTypedTable(Oid reltypeId, Oid reloftypeId)
  {
  	Oid			relid = typeOrDomainTypeRelid(reltypeId);
  	bool		result = false;
  
  	if (relid)
  	{
  		HeapTuple	tp;
  		Form_pg_class reltup;
  
  		tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
  		if (!HeapTupleIsValid(tp))
  			elog(ERROR, "cache lookup failed for relation %u", relid);
  
  		reltup = (Form_pg_class) GETSTRUCT(tp);
  		if (reltup->reloftype == reloftypeId)
  			result = true;
  
  		ReleaseSysCache(tp);
  	}
  
  	return result;
  }
  