text: /* ----------
   * ri_triggers.c
   *
   *	Generic trigger procedures for referential integrity constraint
   *	checks.
   *
   *	Note about memory management: the private hashtables kept here live
   *	across query and transaction boundaries, in fact they live as long as
   *	the backend does.  This works because the hashtable structures
   *	themselves are allocated by dynahash.c in its permanent DynaHashCxt,
   *	and the SPI plans they point to are saved using SPI_keepplan().
   *	There is not currently any provision for throwing away a no-longer-needed
   *	plan --- consider improving this someday.
   *
   *
   * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
   *
   * src/backend/utils/adt/ri_triggers.c
   *
   * ----------
   */
  
  
  /* ----------
   * Internal TODO:
   *
   *		Add MATCH PARTIAL logic.
   * ----------
   */
  
  #include "postgres.h"
  
  #include "access/htup_details.h"
  #include "access/sysattr.h"
  #include "access/xact.h"
  #include "catalog/pg_collation.h"
  #include "catalog/pg_constraint.h"
  #include "catalog/pg_operator.h"
  #include "catalog/pg_type.h"
  #include "commands/trigger.h"
  #include "executor/executor.h"
  #include "executor/spi.h"
  #include "lib/ilist.h"
  #include "parser/parse_coerce.h"
  #include "parser/parse_relation.h"
  #include "miscadmin.h"
  #include "storage/bufmgr.h"
  #include "utils/acl.h"
  #include "utils/builtins.h"
  #include "utils/fmgroids.h"
  #include "utils/guc.h"
  #include "utils/inval.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/rel.h"
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/tqual.h"
  
  
  /* ----------
   * Local definitions
   * ----------
   */
  
  #define RI_MAX_NUMKEYS					INDEX_MAX_KEYS
  
  #define RI_INIT_CONSTRAINTHASHSIZE		64
  #define RI_INIT_QUERYHASHSIZE			(RI_INIT_CONSTRAINTHASHSIZE * 4)
  
  #define RI_KEYS_ALL_NULL				0
  #define RI_KEYS_SOME_NULL				1
  #define RI_KEYS_NONE_NULL				2
  
  /* RI query type codes */
  /* these queries are executed against the PK (referenced) table: */
  #define RI_PLAN_CHECK_LOOKUPPK			1
  #define RI_PLAN_CHECK_LOOKUPPK_FROM_PK	2
  #define RI_PLAN_LAST_ON_PK				RI_PLAN_CHECK_LOOKUPPK_FROM_PK
  /* these queries are executed against the FK (referencing) table: */
  #define RI_PLAN_CASCADE_DEL_DODELETE	3
  #define RI_PLAN_CASCADE_UPD_DOUPDATE	4
  #define RI_PLAN_RESTRICT_DEL_CHECKREF	5
  #define RI_PLAN_RESTRICT_UPD_CHECKREF	6
  #define RI_PLAN_SETNULL_DEL_DOUPDATE	7
  #define RI_PLAN_SETNULL_UPD_DOUPDATE	8
  #define RI_PLAN_SETDEFAULT_DEL_DOUPDATE 9
  #define RI_PLAN_SETDEFAULT_UPD_DOUPDATE 10
  
  #define MAX_QUOTED_NAME_LEN  (NAMEDATALEN*2+3)
  #define MAX_QUOTED_REL_NAME_LEN  (MAX_QUOTED_NAME_LEN*2)
  
  #define RIAttName(rel, attnum)	NameStr(*attnumAttName(rel, attnum))
  #define RIAttType(rel, attnum)	attnumTypeId(rel, attnum)
  #define RIAttCollation(rel, attnum) attnumCollationId(rel, attnum)
  
  #define RI_TRIGTYPE_INSERT 1
  #define RI_TRIGTYPE_UPDATE 2
  #define RI_TRIGTYPE_DELETE 3
  
  
  /* ----------
   * RI_ConstraintInfo
   *
   *	Information extracted from an FK pg_constraint entry.  This is cached in
   *	ri_constraint_cache.
   * ----------
   */
  typedef struct RI_ConstraintInfo
  {
  	Oid			constraint_id;	/* OID of pg_constraint entry (hash key) */
  	bool		valid;			/* successfully initialized? */
  	uint32		oidHashValue;	/* hash value of pg_constraint OID */
  	NameData	conname;		/* name of the FK constraint */
  	Oid			pk_relid;		/* referenced relation */
  	Oid			fk_relid;		/* referencing relation */
  	char		confupdtype;	/* foreign key's ON UPDATE action */
  	char		confdeltype;	/* foreign key's ON DELETE action */
  	char		confmatchtype;	/* foreign key's match type */
  	int			nkeys;			/* number of key columns */
  	int16		pk_attnums[RI_MAX_NUMKEYS];		/* attnums of referenced cols */
  	int16		fk_attnums[RI_MAX_NUMKEYS];		/* attnums of referencing cols */
  	Oid			pf_eq_oprs[RI_MAX_NUMKEYS];		/* equality operators (PK =
  												 * FK) */
  	Oid			pp_eq_oprs[RI_MAX_NUMKEYS];		/* equality operators (PK =
  												 * PK) */
  	Oid			ff_eq_oprs[RI_MAX_NUMKEYS];		/* equality operators (FK =
  												 * FK) */
  	dlist_node	valid_link;		/* Link in list of valid entries */
  } RI_ConstraintInfo;
  
  
  /* ----------
   * RI_QueryKey
   *
   *	The key identifying a prepared SPI plan in our query hashtable
   * ----------
   */
  typedef struct RI_QueryKey
  {
  	Oid			constr_id;		/* OID of pg_constraint entry */
  	int32		constr_queryno; /* query type ID, see RI_PLAN_XXX above */
  } RI_QueryKey;
  
  
  /* ----------
   * RI_QueryHashEntry
   * ----------
   */
  typedef struct RI_QueryHashEntry
  {
  	RI_QueryKey key;
  	SPIPlanPtr	plan;
  } RI_QueryHashEntry;
  
  
  /* ----------
   * RI_CompareKey
   *
   *	The key identifying an entry showing how to compare two values
   * ----------
   */
  typedef struct RI_CompareKey
  {
  	Oid			eq_opr;			/* the equality operator to apply */
  	Oid			typeid;			/* the data type to apply it to */
  } RI_CompareKey;
  
  
  /* ----------
   * RI_CompareHashEntry
   * ----------
   */
  typedef struct RI_CompareHashEntry
  {
  	RI_CompareKey key;
  	bool		valid;			/* successfully initialized? */
  	FmgrInfo	eq_opr_finfo;	/* call info for equality fn */
  	FmgrInfo	cast_func_finfo;	/* in case we must coerce input */
  } RI_CompareHashEntry;
  
  
  /* ----------
   * Local data
   * ----------
   */
  static HTAB *ri_constraint_cache = NULL;
  static HTAB *ri_query_cache = NULL;
  static HTAB *ri_compare_cache = NULL;
  static dlist_head ri_constraint_cache_valid_list;
  static int	ri_constraint_cache_valid_count = 0;
  
  
  /* ----------
   * Local function prototypes
   * ----------
   */
  static bool ri_Check_Pk_Match(Relation pk_rel, Relation fk_rel,
  				  HeapTuple old_row,
  				  const RI_ConstraintInfo *riinfo);
  static Datum ri_restrict_del(TriggerData *trigdata, bool is_no_action);
  static Datum ri_restrict_upd(TriggerData *trigdata, bool is_no_action);
  static void quoteOneName(char *buffer, const char *name);
  static void quoteRelationName(char *buffer, Relation rel);
  static void ri_GenerateQual(StringInfo buf,
  				const char *sep,
  				const char *leftop, Oid leftoptype,
  				Oid opoid,
  				const char *rightop, Oid rightoptype);
  static void ri_GenerateQualCollation(StringInfo buf, Oid collation);
  static int ri_NullCheck(HeapTuple tup,
  			 const RI_ConstraintInfo *riinfo, bool rel_is_pk);
  static void ri_BuildQueryKey(RI_QueryKey *key,
  				 const RI_ConstraintInfo *riinfo,
  				 int32 constr_queryno);
  static bool ri_KeysEqual(Relation rel, HeapTuple oldtup, HeapTuple newtup,
  			 const RI_ConstraintInfo *riinfo, bool rel_is_pk);
  static bool ri_AttributesEqual(Oid eq_opr, Oid typeid,
  				   Datum oldvalue, Datum newvalue);
  
  static void ri_InitHashTables(void);
  static void InvalidateConstraintCacheCallBack(Datum arg, int cacheid, uint32 hashvalue);
  static SPIPlanPtr ri_FetchPreparedPlan(RI_QueryKey *key);
  static void ri_HashPreparedPlan(RI_QueryKey *key, SPIPlanPtr plan);
  static RI_CompareHashEntry *ri_HashCompareOp(Oid eq_opr, Oid typeid);
  
  static void ri_CheckTrigger(FunctionCallInfo fcinfo, const char *funcname,
  				int tgkind);
  static const RI_ConstraintInfo *ri_FetchConstraintInfo(Trigger *trigger,
  					   Relation trig_rel, bool rel_is_pk);
  static const RI_ConstraintInfo *ri_LoadConstraintInfo(Oid constraintOid);
  static SPIPlanPtr ri_PlanCheck(const char *querystr, int nargs, Oid *argtypes,
  			 RI_QueryKey *qkey, Relation fk_rel, Relation pk_rel,
  			 bool cache_plan);
  static bool ri_PerformCheck(const RI_ConstraintInfo *riinfo,
  				RI_QueryKey *qkey, SPIPlanPtr qplan,
  				Relation fk_rel, Relation pk_rel,
  				HeapTuple old_tuple, HeapTuple new_tuple,
  				bool detectNewRows, int expect_OK);
  static void ri_ExtractValues(Relation rel, HeapTuple tup,
  				 const RI_ConstraintInfo *riinfo, bool rel_is_pk,
  				 Datum *vals, char *nulls);
  static void ri_ReportViolation(const RI_ConstraintInfo *riinfo,
  				   Relation pk_rel, Relation fk_rel,
  				   HeapTuple violator, TupleDesc tupdesc,
  				   int queryno, bool spi_err);
  
  
  /* ----------
   * RI_FKey_check -
   *
   *	Check foreign key existence (combined for INSERT and UPDATE).
   * ----------
   */
  static Datum
  RI_FKey_check(TriggerData *trigdata)
  {
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	new_row;
  	Buffer		new_row_buf;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, false);
  
  	if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
  	{
  		new_row = trigdata->tg_newtuple;
  		new_row_buf = trigdata->tg_newtuplebuf;
  	}
  	else
  	{
  		new_row = trigdata->tg_trigtuple;
  		new_row_buf = trigdata->tg_trigtuplebuf;
  	}
  
  	/*
  	 * We should not even consider checking the row if it is no longer valid,
  	 * since it was either deleted (so the deferred check should be skipped)
  	 * or updated (in which case only the latest version of the row should be
  	 * checked).  Test its liveness according to SnapshotSelf.  We need pin
  	 * and lock on the buffer to call HeapTupleSatisfiesVisibility.  Caller
  	 * should be holding pin, but not lock.
  	 */
  	LockBuffer(new_row_buf, BUFFER_LOCK_SHARE);
  	if (!HeapTupleSatisfiesVisibility(new_row, SnapshotSelf, new_row_buf))
  	{
  		LockBuffer(new_row_buf, BUFFER_LOCK_UNLOCK);
  		return PointerGetDatum(NULL);
  	}
  	LockBuffer(new_row_buf, BUFFER_LOCK_UNLOCK);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables.
  	 *
  	 * pk_rel is opened in RowShareLock mode since that's what our eventual
  	 * SELECT FOR KEY SHARE will get on it.
  	 */
  	fk_rel = trigdata->tg_relation;
  	pk_rel = heap_open(riinfo->pk_relid, RowShareLock);
  
  	if (riinfo->confmatchtype == FKCONSTR_MATCH_PARTIAL)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("MATCH PARTIAL not yet implemented")));
  
  	switch (ri_NullCheck(new_row, riinfo, false))
  	{
  		case RI_KEYS_ALL_NULL:
  
  			/*
  			 * No further check needed - an all-NULL key passes every type of
  			 * foreign key constraint.
  			 */
  			heap_close(pk_rel, RowShareLock);
  			return PointerGetDatum(NULL);
  
  		case RI_KEYS_SOME_NULL:
  
  			/*
  			 * This is the only case that differs between the three kinds of
  			 * MATCH.
  			 */
  			switch (riinfo->confmatchtype)
  			{
  				case FKCONSTR_MATCH_FULL:
  
  					/*
  					 * Not allowed - MATCH FULL says either all or none of the
  					 * attributes can be NULLs
  					 */
  					ereport(ERROR,
  							(errcode(ERRCODE_FOREIGN_KEY_VIOLATION),
  							 errmsg("insert or update on table \"%s\" violates foreign key constraint \"%s\"",
  									RelationGetRelationName(fk_rel),
  									NameStr(riinfo->conname)),
  							 errdetail("MATCH FULL does not allow mixing of null and nonnull key values."),
  							 errtableconstraint(fk_rel,
  												NameStr(riinfo->conname))));
  					heap_close(pk_rel, RowShareLock);
  					return PointerGetDatum(NULL);
  
  				case FKCONSTR_MATCH_SIMPLE:
  
  					/*
  					 * MATCH SIMPLE - if ANY column is null, the key passes
  					 * the constraint.
  					 */
  					heap_close(pk_rel, RowShareLock);
  					return PointerGetDatum(NULL);
  
  				case FKCONSTR_MATCH_PARTIAL:
  
  					/*
  					 * MATCH PARTIAL - all non-null columns must match. (not
  					 * implemented, can be done by modifying the query below
  					 * to only include non-null columns, or by writing a
  					 * special version here)
  					 */
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("MATCH PARTIAL not yet implemented")));
  					heap_close(pk_rel, RowShareLock);
  					return PointerGetDatum(NULL);
  
  				default:
  					elog(ERROR, "unrecognized confmatchtype: %d",
  						 riinfo->confmatchtype);
  					break;
  			}
  
  		case RI_KEYS_NONE_NULL:
  
  			/*
  			 * Have a full qualified key - continue below for all three kinds
  			 * of MATCH.
  			 */
  			break;
  	}
  
  	if (SPI_connect() != SPI_OK_CONNECT)
  		elog(ERROR, "SPI_connect failed");
  
  	/*
  	 * Fetch or prepare a saved plan for the real check
  	 */
  	ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_CHECK_LOOKUPPK);
  
  	if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  	{
  		StringInfoData querybuf;
  		char		pkrelname[MAX_QUOTED_REL_NAME_LEN];
  		char		attname[MAX_QUOTED_NAME_LEN];
  		char		paramname[16];
  		const char *querysep;
  		Oid			queryoids[RI_MAX_NUMKEYS];
  
  		/* ----------
  		 * The query string built is
  		 *	SELECT 1 FROM ONLY <pktable> x WHERE pkatt1 = $1 [AND ...]
  		 *		   FOR KEY SHARE OF x
  		 * The type id's for the $ parameters are those of the
  		 * corresponding FK attributes.
  		 * ----------
  		 */
  		initStringInfo(&querybuf);
  		quoteRelationName(pkrelname, pk_rel);
  		appendStringInfo(&querybuf, "SELECT 1 FROM ONLY %s x", pkrelname);
  		querysep = "WHERE";
  		for (i = 0; i < riinfo->nkeys; i++)
  		{
  			Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  			Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  			quoteOneName(attname,
  						 RIAttName(pk_rel, riinfo->pk_attnums[i]));
  			sprintf(paramname, "$%d", i + 1);
  			ri_GenerateQual(&querybuf, querysep,
  							attname, pk_type,
  							riinfo->pf_eq_oprs[i],
  							paramname, fk_type);
  			querysep = "AND";
  			queryoids[i] = fk_type;
  		}
  		appendStringInfoString(&querybuf, " FOR KEY SHARE OF x");
  
  		/* Prepare and save the plan */
  		qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  							 &qkey, fk_rel, pk_rel, true);
  	}
  
  	/*
  	 * Now check that foreign key exists in PK table
  	 */
  	ri_PerformCheck(riinfo, &qkey, qplan,
  					fk_rel, pk_rel,
  					NULL, new_row,
  					false,
  					SPI_OK_SELECT);
  
  	if (SPI_finish() != SPI_OK_FINISH)
  		elog(ERROR, "SPI_finish failed");
  
  	heap_close(pk_rel, RowShareLock);
  
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_check_ins -
   *
   *	Check foreign key existence at insert event on FK table.
   * ----------
   */
  Datum
  RI_FKey_check_ins(PG_FUNCTION_ARGS)
  {
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_check_ins", RI_TRIGTYPE_INSERT);
  
  	/*
  	 * Share code with UPDATE case.
  	 */
  	return RI_FKey_check((TriggerData *) fcinfo->context);
  }
  
  
  /* ----------
   * RI_FKey_check_upd -
   *
   *	Check foreign key existence at update event on FK table.
   * ----------
   */
  Datum
  RI_FKey_check_upd(PG_FUNCTION_ARGS)
  {
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_check_upd", RI_TRIGTYPE_UPDATE);
  
  	/*
  	 * Share code with INSERT case.
  	 */
  	return RI_FKey_check((TriggerData *) fcinfo->context);
  }
  
  
  /* ----------
   * ri_Check_Pk_Match
   *
   * Check to see if another PK row has been created that provides the same
   * key values as the "old_row" that's been modified or deleted in our trigger
   * event.  Returns true if a match is found in the PK table.
   *
   * We assume the caller checked that the old_row contains no NULL key values,
   * since otherwise a match is impossible.
   * ----------
   */
  static bool
  ri_Check_Pk_Match(Relation pk_rel, Relation fk_rel,
  				  HeapTuple old_row,
  				  const RI_ConstraintInfo *riinfo)
  {
  	SPIPlanPtr	qplan;
  	RI_QueryKey qkey;
  	int			i;
  	bool		result;
  
  	/* Only called for non-null rows */
  	Assert(ri_NullCheck(old_row, riinfo, true) == RI_KEYS_NONE_NULL);
  
  	if (SPI_connect() != SPI_OK_CONNECT)
  		elog(ERROR, "SPI_connect failed");
  
  	/*
  	 * Fetch or prepare a saved plan for checking PK table with values coming
  	 * from a PK row
  	 */
  	ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_CHECK_LOOKUPPK_FROM_PK);
  
  	if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  	{
  		StringInfoData querybuf;
  		char		pkrelname[MAX_QUOTED_REL_NAME_LEN];
  		char		attname[MAX_QUOTED_NAME_LEN];
  		char		paramname[16];
  		const char *querysep;
  		Oid			queryoids[RI_MAX_NUMKEYS];
  
  		/* ----------
  		 * The query string built is
  		 *	SELECT 1 FROM ONLY <pktable> x WHERE pkatt1 = $1 [AND ...]
  		 *		   FOR KEY SHARE OF x
  		 * The type id's for the $ parameters are those of the
  		 * PK attributes themselves.
  		 * ----------
  		 */
  		initStringInfo(&querybuf);
  		quoteRelationName(pkrelname, pk_rel);
  		appendStringInfo(&querybuf, "SELECT 1 FROM ONLY %s x", pkrelname);
  		querysep = "WHERE";
  		for (i = 0; i < riinfo->nkeys; i++)
  		{
  			Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  
  			quoteOneName(attname,
  						 RIAttName(pk_rel, riinfo->pk_attnums[i]));
  			sprintf(paramname, "$%d", i + 1);
  			ri_GenerateQual(&querybuf, querysep,
  							attname, pk_type,
  							riinfo->pp_eq_oprs[i],
  							paramname, pk_type);
  			querysep = "AND";
  			queryoids[i] = pk_type;
  		}
  		appendStringInfoString(&querybuf, " FOR KEY SHARE OF x");
  
  		/* Prepare and save the plan */
  		qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  							 &qkey, fk_rel, pk_rel, true);
  	}
  
  	/*
  	 * We have a plan now. Run it.
  	 */
  	result = ri_PerformCheck(riinfo, &qkey, qplan,
  							 fk_rel, pk_rel,
  							 old_row, NULL,
  							 true,		/* treat like update */
  							 SPI_OK_SELECT);
  
  	if (SPI_finish() != SPI_OK_FINISH)
  		elog(ERROR, "SPI_finish failed");
  
  	return result;
  }
  
  
  /* ----------
   * RI_FKey_noaction_del -
   *
   *	Give an error and roll back the current transaction if the
   *	delete has resulted in a violation of the given referential
   *	integrity constraint.
   * ----------
   */
  Datum
  RI_FKey_noaction_del(PG_FUNCTION_ARGS)
  {
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_noaction_del", RI_TRIGTYPE_DELETE);
  
  	/*
  	 * Share code with RESTRICT case.
  	 */
  	return ri_restrict_del((TriggerData *) fcinfo->context, true);
  }
  
  /* ----------
   * RI_FKey_restrict_del -
   *
   *	Restrict delete from PK table to rows unreferenced by foreign key.
   *
   *	The SQL standard intends that this referential action occur exactly when
   *	the delete is performed, rather than after.  This appears to be
   *	the only difference between "NO ACTION" and "RESTRICT".  In Postgres
   *	we still implement this as an AFTER trigger, but it's non-deferrable.
   * ----------
   */
  Datum
  RI_FKey_restrict_del(PG_FUNCTION_ARGS)
  {
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_restrict_del", RI_TRIGTYPE_DELETE);
  
  	/*
  	 * Share code with NO ACTION case.
  	 */
  	return ri_restrict_del((TriggerData *) fcinfo->context, false);
  }
  
  /* ----------
   * ri_restrict_del -
   *
   *	Common code for ON DELETE RESTRICT and ON DELETE NO ACTION.
   * ----------
   */
  static Datum
  ri_restrict_del(TriggerData *trigdata, bool is_no_action)
  {
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the old tuple.
  	 *
  	 * fk_rel is opened in RowShareLock mode since that's what our eventual
  	 * SELECT FOR KEY SHARE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowShareLock);
  	pk_rel = trigdata->tg_relation;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 9) a) iv):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON DELETE RESTRICT
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowShareLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			/*
  			 * If another PK row now exists providing the old key values, we
  			 * should not do anything.  However, this check should only be
  			 * made in the NO ACTION case; in RESTRICT cases we don't wish to
  			 * allow another row to be substituted.
  			 */
  			if (is_no_action &&
  				ri_Check_Pk_Match(pk_rel, fk_rel, old_row, riinfo))
  			{
  				heap_close(fk_rel, RowShareLock);
  				return PointerGetDatum(NULL);
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the restrict delete lookup
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_RESTRICT_DEL_CHECKREF);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  
  				/* ----------
  				 * The query string built is
  				 *	SELECT 1 FROM ONLY <fktable> x WHERE $1 = fkatt1 [AND ...]
  				 *		   FOR KEY SHARE OF x
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "SELECT 1 FROM ONLY %s x",
  								 fkrelname);
  				querysep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&querybuf, querysep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = "AND";
  					queryoids[i] = pk_type;
  				}
  				appendStringInfoString(&querybuf, " FOR KEY SHARE OF x");
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to check for existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_SELECT);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowShareLock);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL restrict delete.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_noaction_upd -
   *
   *	Give an error and roll back the current transaction if the
   *	update has resulted in a violation of the given referential
   *	integrity constraint.
   * ----------
   */
  Datum
  RI_FKey_noaction_upd(PG_FUNCTION_ARGS)
  {
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_noaction_upd", RI_TRIGTYPE_UPDATE);
  
  	/*
  	 * Share code with RESTRICT case.
  	 */
  	return ri_restrict_upd((TriggerData *) fcinfo->context, true);
  }
  
  /* ----------
   * RI_FKey_restrict_upd -
   *
   *	Restrict update of PK to rows unreferenced by foreign key.
   *
   *	The SQL standard intends that this referential action occur exactly when
   *	the update is performed, rather than after.  This appears to be
   *	the only difference between "NO ACTION" and "RESTRICT".  In Postgres
   *	we still implement this as an AFTER trigger, but it's non-deferrable.
   * ----------
   */
  Datum
  RI_FKey_restrict_upd(PG_FUNCTION_ARGS)
  {
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_restrict_upd", RI_TRIGTYPE_UPDATE);
  
  	/*
  	 * Share code with NO ACTION case.
  	 */
  	return ri_restrict_upd((TriggerData *) fcinfo->context, false);
  }
  
  /* ----------
   * ri_restrict_upd -
   *
   *	Common code for ON UPDATE RESTRICT and ON UPDATE NO ACTION.
   * ----------
   */
  static Datum
  ri_restrict_upd(TriggerData *trigdata, bool is_no_action)
  {
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	new_row;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the new and
  	 * old tuple.
  	 *
  	 * fk_rel is opened in RowShareLock mode since that's what our eventual
  	 * SELECT FOR KEY SHARE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowShareLock);
  	pk_rel = trigdata->tg_relation;
  	new_row = trigdata->tg_newtuple;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 10) a) iv):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON UPDATE RESTRICT
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowShareLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			/*
  			 * No need to check anything if old and new keys are equal
  			 */
  			if (ri_KeysEqual(pk_rel, old_row, new_row, riinfo, true))
  			{
  				heap_close(fk_rel, RowShareLock);
  				return PointerGetDatum(NULL);
  			}
  
  			/*
  			 * If another PK row now exists providing the old key values, we
  			 * should not do anything.  However, this check should only be
  			 * made in the NO ACTION case; in RESTRICT cases we don't wish to
  			 * allow another row to be substituted.
  			 */
  			if (is_no_action &&
  				ri_Check_Pk_Match(pk_rel, fk_rel, old_row, riinfo))
  			{
  				heap_close(fk_rel, RowShareLock);
  				return PointerGetDatum(NULL);
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the restrict update lookup
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_RESTRICT_UPD_CHECKREF);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  
  				/* ----------
  				 * The query string built is
  				 *	SELECT 1 FROM ONLY <fktable> WHERE $1 = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "SELECT 1 FROM ONLY %s x",
  								 fkrelname);
  				querysep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&querybuf, querysep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = "AND";
  					queryoids[i] = pk_type;
  				}
  				appendStringInfoString(&querybuf, " FOR KEY SHARE OF x");
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to check for existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_SELECT);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowShareLock);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL restrict update.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_cascade_del -
   *
   *	Cascaded delete foreign key references at delete event on PK table.
   * ----------
   */
  Datum
  RI_FKey_cascade_del(PG_FUNCTION_ARGS)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_cascade_del", RI_TRIGTYPE_DELETE);
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the old tuple.
  	 *
  	 * fk_rel is opened in RowExclusiveLock mode since that's what our
  	 * eventual DELETE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowExclusiveLock);
  	pk_rel = trigdata->tg_relation;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 9) a) i):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON DELETE CASCADE
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowExclusiveLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the cascaded delete
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_CASCADE_DEL_DODELETE);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  
  				/* ----------
  				 * The query string built is
  				 *	DELETE FROM ONLY <fktable> WHERE $1 = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "DELETE FROM ONLY %s", fkrelname);
  				querysep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&querybuf, querysep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = "AND";
  					queryoids[i] = pk_type;
  				}
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Build up the arguments from the key values
  			 * in the deleted PK tuple and delete the referencing rows
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_DELETE);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowExclusiveLock);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL cascaded delete.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_cascade_upd -
   *
   *	Cascaded update foreign key references at update event on PK table.
   * ----------
   */
  Datum
  RI_FKey_cascade_upd(PG_FUNCTION_ARGS)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	new_row;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  	int			j;
  
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_cascade_upd", RI_TRIGTYPE_UPDATE);
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the new and
  	 * old tuple.
  	 *
  	 * fk_rel is opened in RowExclusiveLock mode since that's what our
  	 * eventual UPDATE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowExclusiveLock);
  	pk_rel = trigdata->tg_relation;
  	new_row = trigdata->tg_newtuple;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 10) a) i):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON UPDATE CASCADE
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowExclusiveLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			/*
  			 * No need to do anything if old and new keys are equal
  			 */
  			if (ri_KeysEqual(pk_rel, old_row, new_row, riinfo, true))
  			{
  				heap_close(fk_rel, RowExclusiveLock);
  				return PointerGetDatum(NULL);
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the cascaded update
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_CASCADE_UPD_DOUPDATE);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				StringInfoData qualbuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				const char *qualsep;
  				Oid			queryoids[RI_MAX_NUMKEYS * 2];
  
  				/* ----------
  				 * The query string built is
  				 *	UPDATE ONLY <fktable> SET fkatt1 = $1 [, ...]
  				 *			WHERE $n = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.  Note that we are assuming
  				 * there is an assignment cast from the PK to the FK type;
  				 * else the parser will fail.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				initStringInfo(&qualbuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "UPDATE ONLY %s SET", fkrelname);
  				querysep = "";
  				qualsep = "WHERE";
  				for (i = 0, j = riinfo->nkeys; i < riinfo->nkeys; i++, j++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					appendStringInfo(&querybuf,
  									 "%s %s = $%d",
  									 querysep, attname, i + 1);
  					sprintf(paramname, "$%d", j + 1);
  					ri_GenerateQual(&qualbuf, qualsep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = ",";
  					qualsep = "AND";
  					queryoids[i] = pk_type;
  					queryoids[j] = pk_type;
  				}
  				appendStringInfoString(&querybuf, qualbuf.data);
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys * 2, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to update the existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, new_row,
  							true,		/* must detect new rows */
  							SPI_OK_UPDATE);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowExclusiveLock);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL cascade update.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_setnull_del -
   *
   *	Set foreign key references to NULL values at delete event on PK table.
   * ----------
   */
  Datum
  RI_FKey_setnull_del(PG_FUNCTION_ARGS)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_setnull_del", RI_TRIGTYPE_DELETE);
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the old tuple.
  	 *
  	 * fk_rel is opened in RowExclusiveLock mode since that's what our
  	 * eventual UPDATE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowExclusiveLock);
  	pk_rel = trigdata->tg_relation;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 9) a) ii):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON DELETE SET NULL
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowExclusiveLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the set null delete operation
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_SETNULL_DEL_DOUPDATE);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				StringInfoData qualbuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				const char *qualsep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  
  				/* ----------
  				 * The query string built is
  				 *	UPDATE ONLY <fktable> SET fkatt1 = NULL [, ...]
  				 *			WHERE $1 = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				initStringInfo(&qualbuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "UPDATE ONLY %s SET", fkrelname);
  				querysep = "";
  				qualsep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					appendStringInfo(&querybuf,
  									 "%s %s = NULL",
  									 querysep, attname);
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&qualbuf, qualsep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = ",";
  					qualsep = "AND";
  					queryoids[i] = pk_type;
  				}
  				appendStringInfoString(&querybuf, qualbuf.data);
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to check for existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_UPDATE);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowExclusiveLock);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL set null delete.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_setnull_upd -
   *
   *	Set foreign key references to NULL at update event on PK table.
   * ----------
   */
  Datum
  RI_FKey_setnull_upd(PG_FUNCTION_ARGS)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	new_row;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  	int			i;
  
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_setnull_upd", RI_TRIGTYPE_UPDATE);
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the old tuple.
  	 *
  	 * fk_rel is opened in RowExclusiveLock mode since that's what our
  	 * eventual UPDATE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowExclusiveLock);
  	pk_rel = trigdata->tg_relation;
  	new_row = trigdata->tg_newtuple;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 10) a) ii):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON UPDATE SET NULL
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowExclusiveLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			/*
  			 * No need to do anything if old and new keys are equal
  			 */
  			if (ri_KeysEqual(pk_rel, old_row, new_row, riinfo, true))
  			{
  				heap_close(fk_rel, RowExclusiveLock);
  				return PointerGetDatum(NULL);
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the set null update operation
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_SETNULL_UPD_DOUPDATE);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				StringInfoData qualbuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				const char *qualsep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  
  				/* ----------
  				 * The query string built is
  				 *	UPDATE ONLY <fktable> SET fkatt1 = NULL [, ...]
  				 *			WHERE $1 = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				initStringInfo(&qualbuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "UPDATE ONLY %s SET", fkrelname);
  				querysep = "";
  				qualsep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					appendStringInfo(&querybuf,
  									 "%s %s = NULL",
  									 querysep, attname);
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&qualbuf, qualsep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = ",";
  					qualsep = "AND";
  					queryoids[i] = pk_type;
  				}
  				appendStringInfoString(&querybuf, qualbuf.data);
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to update the existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_UPDATE);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowExclusiveLock);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL set null update.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_setdefault_del -
   *
   *	Set foreign key references to defaults at delete event on PK table.
   * ----------
   */
  Datum
  RI_FKey_setdefault_del(PG_FUNCTION_ARGS)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_setdefault_del", RI_TRIGTYPE_DELETE);
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the old tuple.
  	 *
  	 * fk_rel is opened in RowExclusiveLock mode since that's what our
  	 * eventual UPDATE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowExclusiveLock);
  	pk_rel = trigdata->tg_relation;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 9) a) iii):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON DELETE SET DEFAULT
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowExclusiveLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the set default delete
  			 * operation
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_SETDEFAULT_DEL_DOUPDATE);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				StringInfoData qualbuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				const char *qualsep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  				int			i;
  
  				/* ----------
  				 * The query string built is
  				 *	UPDATE ONLY <fktable> SET fkatt1 = DEFAULT [, ...]
  				 *			WHERE $1 = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				initStringInfo(&qualbuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "UPDATE ONLY %s SET", fkrelname);
  				querysep = "";
  				qualsep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					appendStringInfo(&querybuf,
  									 "%s %s = DEFAULT",
  									 querysep, attname);
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&qualbuf, qualsep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = ",";
  					qualsep = "AND";
  					queryoids[i] = pk_type;
  				}
  				appendStringInfoString(&querybuf, qualbuf.data);
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to update the existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_UPDATE);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowExclusiveLock);
  
  			/*
  			 * If we just deleted the PK row whose key was equal to the FK
  			 * columns' default values, and a referencing row exists in the FK
  			 * table, we would have updated that row to the same values it
  			 * already had --- and RI_FKey_fk_upd_check_required would hence
  			 * believe no check is necessary.  So we need to do another lookup
  			 * now and in case a reference still exists, abort the operation.
  			 * That is already implemented in the NO ACTION trigger, so just
  			 * run it.  (This recheck is only needed in the SET DEFAULT case,
  			 * since CASCADE would remove such rows, while SET NULL is certain
  			 * to result in rows that satisfy the FK constraint.)
  			 */
  			RI_FKey_noaction_del(fcinfo);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL set default delete.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_setdefault_upd -
   *
   *	Set foreign key references to defaults at update event on PK table.
   * ----------
   */
  Datum
  RI_FKey_setdefault_upd(PG_FUNCTION_ARGS)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  	const RI_ConstraintInfo *riinfo;
  	Relation	fk_rel;
  	Relation	pk_rel;
  	HeapTuple	new_row;
  	HeapTuple	old_row;
  	RI_QueryKey qkey;
  	SPIPlanPtr	qplan;
  
  	/*
  	 * Check that this is a valid trigger call on the right time and event.
  	 */
  	ri_CheckTrigger(fcinfo, "RI_FKey_setdefault_upd", RI_TRIGTYPE_UPDATE);
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigdata->tg_trigger,
  									trigdata->tg_relation, true);
  
  	/*
  	 * Get the relation descriptors of the FK and PK tables and the old tuple.
  	 *
  	 * fk_rel is opened in RowExclusiveLock mode since that's what our
  	 * eventual UPDATE will get on it.
  	 */
  	fk_rel = heap_open(riinfo->fk_relid, RowExclusiveLock);
  	pk_rel = trigdata->tg_relation;
  	new_row = trigdata->tg_newtuple;
  	old_row = trigdata->tg_trigtuple;
  
  	switch (riinfo->confmatchtype)
  	{
  			/* ----------
  			 * SQL:2008 15.17 <Execution of referential actions>
  			 *	General rules 10) a) iii):
  			 *		MATCH SIMPLE/FULL
  			 *			... ON UPDATE SET DEFAULT
  			 * ----------
  			 */
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  			switch (ri_NullCheck(old_row, riinfo, true))
  			{
  				case RI_KEYS_ALL_NULL:
  				case RI_KEYS_SOME_NULL:
  
  					/*
  					 * No check needed - there cannot be any reference to old
  					 * key if it contains a NULL
  					 */
  					heap_close(fk_rel, RowExclusiveLock);
  					return PointerGetDatum(NULL);
  
  				case RI_KEYS_NONE_NULL:
  
  					/*
  					 * Have a full qualified key - continue below
  					 */
  					break;
  			}
  
  			/*
  			 * No need to do anything if old and new keys are equal
  			 */
  			if (ri_KeysEqual(pk_rel, old_row, new_row, riinfo, true))
  			{
  				heap_close(fk_rel, RowExclusiveLock);
  				return PointerGetDatum(NULL);
  			}
  
  			if (SPI_connect() != SPI_OK_CONNECT)
  				elog(ERROR, "SPI_connect failed");
  
  			/*
  			 * Fetch or prepare a saved plan for the set default update
  			 * operation
  			 */
  			ri_BuildQueryKey(&qkey, riinfo, RI_PLAN_SETDEFAULT_UPD_DOUPDATE);
  
  			if ((qplan = ri_FetchPreparedPlan(&qkey)) == NULL)
  			{
  				StringInfoData querybuf;
  				StringInfoData qualbuf;
  				char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  				char		attname[MAX_QUOTED_NAME_LEN];
  				char		paramname[16];
  				const char *querysep;
  				const char *qualsep;
  				Oid			queryoids[RI_MAX_NUMKEYS];
  				int			i;
  
  				/* ----------
  				 * The query string built is
  				 *	UPDATE ONLY <fktable> SET fkatt1 = DEFAULT [, ...]
  				 *			WHERE $1 = fkatt1 [AND ...]
  				 * The type id's for the $ parameters are those of the
  				 * corresponding PK attributes.
  				 * ----------
  				 */
  				initStringInfo(&querybuf);
  				initStringInfo(&qualbuf);
  				quoteRelationName(fkrelname, fk_rel);
  				appendStringInfo(&querybuf, "UPDATE ONLY %s SET", fkrelname);
  				querysep = "";
  				qualsep = "WHERE";
  				for (i = 0; i < riinfo->nkeys; i++)
  				{
  					Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  					Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  
  					quoteOneName(attname,
  								 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  					appendStringInfo(&querybuf,
  									 "%s %s = DEFAULT",
  									 querysep, attname);
  					sprintf(paramname, "$%d", i + 1);
  					ri_GenerateQual(&qualbuf, qualsep,
  									paramname, pk_type,
  									riinfo->pf_eq_oprs[i],
  									attname, fk_type);
  					querysep = ",";
  					qualsep = "AND";
  					queryoids[i] = pk_type;
  				}
  				appendStringInfoString(&querybuf, qualbuf.data);
  
  				/* Prepare and save the plan */
  				qplan = ri_PlanCheck(querybuf.data, riinfo->nkeys, queryoids,
  									 &qkey, fk_rel, pk_rel, true);
  			}
  
  			/*
  			 * We have a plan now. Run it to update the existing references.
  			 */
  			ri_PerformCheck(riinfo, &qkey, qplan,
  							fk_rel, pk_rel,
  							old_row, NULL,
  							true,		/* must detect new rows */
  							SPI_OK_UPDATE);
  
  			if (SPI_finish() != SPI_OK_FINISH)
  				elog(ERROR, "SPI_finish failed");
  
  			heap_close(fk_rel, RowExclusiveLock);
  
  			/*
  			 * If we just updated the PK row whose key was equal to the FK
  			 * columns' default values, and a referencing row exists in the FK
  			 * table, we would have updated that row to the same values it
  			 * already had --- and RI_FKey_fk_upd_check_required would hence
  			 * believe no check is necessary.  So we need to do another lookup
  			 * now and in case a reference still exists, abort the operation.
  			 * That is already implemented in the NO ACTION trigger, so just
  			 * run it.  (This recheck is only needed in the SET DEFAULT case,
  			 * since CASCADE must change the FK key values, while SET NULL is
  			 * certain to result in rows that satisfy the FK constraint.)
  			 */
  			RI_FKey_noaction_upd(fcinfo);
  
  			return PointerGetDatum(NULL);
  
  			/*
  			 * Handle MATCH PARTIAL set default update.
  			 */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			return PointerGetDatum(NULL);
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return PointerGetDatum(NULL);
  }
  
  
  /* ----------
   * RI_FKey_pk_upd_check_required -
   *
   *	Check if we really need to fire the RI trigger for an update to a PK
   *	relation.  This is called by the AFTER trigger queue manager to see if
   *	it can skip queuing an instance of an RI trigger.  Returns TRUE if the
   *	trigger must be fired, FALSE if we can prove the constraint will still
   *	be satisfied.
   * ----------
   */
  bool
  RI_FKey_pk_upd_check_required(Trigger *trigger, Relation pk_rel,
  							  HeapTuple old_row, HeapTuple new_row)
  {
  	const RI_ConstraintInfo *riinfo;
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigger, pk_rel, true);
  
  	switch (riinfo->confmatchtype)
  	{
  		case FKCONSTR_MATCH_SIMPLE:
  		case FKCONSTR_MATCH_FULL:
  
  			/*
  			 * If any old key value is NULL, the row could not have been
  			 * referenced by an FK row, so no check is needed.
  			 */
  			if (ri_NullCheck(old_row, riinfo, true) != RI_KEYS_NONE_NULL)
  				return false;
  
  			/* If all old and new key values are equal, no check is needed */
  			if (ri_KeysEqual(pk_rel, old_row, new_row, riinfo, true))
  				return false;
  
  			/* Else we need to fire the trigger. */
  			return true;
  
  			/* Handle MATCH PARTIAL check. */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			break;
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return false;
  }
  
  /* ----------
   * RI_FKey_fk_upd_check_required -
   *
   *	Check if we really need to fire the RI trigger for an update to an FK
   *	relation.  This is called by the AFTER trigger queue manager to see if
   *	it can skip queuing an instance of an RI trigger.  Returns TRUE if the
   *	trigger must be fired, FALSE if we can prove the constraint will still
   *	be satisfied.
   * ----------
   */
  bool
  RI_FKey_fk_upd_check_required(Trigger *trigger, Relation fk_rel,
  							  HeapTuple old_row, HeapTuple new_row)
  {
  	const RI_ConstraintInfo *riinfo;
  
  	/*
  	 * Get arguments.
  	 */
  	riinfo = ri_FetchConstraintInfo(trigger, fk_rel, false);
  
  	switch (riinfo->confmatchtype)
  	{
  		case FKCONSTR_MATCH_SIMPLE:
  
  			/*
  			 * If any new key value is NULL, the row must satisfy the
  			 * constraint, so no check is needed.
  			 */
  			if (ri_NullCheck(new_row, riinfo, false) != RI_KEYS_NONE_NULL)
  				return false;
  
  			/*
  			 * If the original row was inserted by our own transaction, we
  			 * must fire the trigger whether or not the keys are equal.  This
  			 * is because our UPDATE will invalidate the INSERT so that the
  			 * INSERT RI trigger will not do anything; so we had better do the
  			 * UPDATE check.  (We could skip this if we knew the INSERT
  			 * trigger already fired, but there is no easy way to know that.)
  			 */
  			if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetXmin(old_row->t_data)))
  				return true;
  
  			/* If all old and new key values are equal, no check is needed */
  			if (ri_KeysEqual(fk_rel, old_row, new_row, riinfo, false))
  				return false;
  
  			/* Else we need to fire the trigger. */
  			return true;
  
  		case FKCONSTR_MATCH_FULL:
  
  			/*
  			 * If all new key values are NULL, the row must satisfy the
  			 * constraint, so no check is needed.  On the other hand, if only
  			 * some of them are NULL, the row must fail the constraint.  We
  			 * must not throw error here, because the row might get
  			 * invalidated before the constraint is to be checked, but we
  			 * should queue the event to apply the check later.
  			 */
  			switch (ri_NullCheck(new_row, riinfo, false))
  			{
  				case RI_KEYS_ALL_NULL:
  					return false;
  				case RI_KEYS_SOME_NULL:
  					return true;
  				case RI_KEYS_NONE_NULL:
  					break;		/* continue with the check */
  			}
  
  			/*
  			 * If the original row was inserted by our own transaction, we
  			 * must fire the trigger whether or not the keys are equal.  This
  			 * is because our UPDATE will invalidate the INSERT so that the
  			 * INSERT RI trigger will not do anything; so we had better do the
  			 * UPDATE check.  (We could skip this if we knew the INSERT
  			 * trigger already fired, but there is no easy way to know that.)
  			 */
  			if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetXmin(old_row->t_data)))
  				return true;
  
  			/* If all old and new key values are equal, no check is needed */
  			if (ri_KeysEqual(fk_rel, old_row, new_row, riinfo, false))
  				return false;
  
  			/* Else we need to fire the trigger. */
  			return true;
  
  			/* Handle MATCH PARTIAL check. */
  		case FKCONSTR_MATCH_PARTIAL:
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("MATCH PARTIAL not yet implemented")));
  			break;
  
  		default:
  			elog(ERROR, "unrecognized confmatchtype: %d",
  				 riinfo->confmatchtype);
  			break;
  	}
  
  	/* Never reached */
  	return false;
  }
  
  /* ----------
   * RI_Initial_Check -
   *
   *	Check an entire table for non-matching values using a single query.
   *	This is not a trigger procedure, but is called during ALTER TABLE
   *	ADD FOREIGN KEY to validate the initial table contents.
   *
   *	We expect that the caller has made provision to prevent any problems
   *	caused by concurrent actions. This could be either by locking rel and
   *	pkrel at ShareRowExclusiveLock or higher, or by otherwise ensuring
   *	that triggers implementing the checks are already active.
   *	Hence, we do not need to lock individual rows for the check.
   *
   *	If the check fails because the current user doesn't have permissions
   *	to read both tables, return false to let our caller know that they will
   *	need to do something else to check the constraint.
   * ----------
   */
  bool
  RI_Initial_Check(Trigger *trigger, Relation fk_rel, Relation pk_rel)
  {
  	const RI_ConstraintInfo *riinfo;
  	StringInfoData querybuf;
  	char		pkrelname[MAX_QUOTED_REL_NAME_LEN];
  	char		fkrelname[MAX_QUOTED_REL_NAME_LEN];
  	char		pkattname[MAX_QUOTED_NAME_LEN + 3];
  	char		fkattname[MAX_QUOTED_NAME_LEN + 3];
  	RangeTblEntry *pkrte;
  	RangeTblEntry *fkrte;
  	const char *sep;
  	int			i;
  	int			save_nestlevel;
  	char		workmembuf[32];
  	int			spi_result;
  	SPIPlanPtr	qplan;
  
  	/* Fetch constraint info. */
  	riinfo = ri_FetchConstraintInfo(trigger, fk_rel, false);
  
  	/*
  	 * Check to make sure current user has enough permissions to do the test
  	 * query.  (If not, caller can fall back to the trigger method, which
  	 * works because it changes user IDs on the fly.)
  	 *
  	 * XXX are there any other show-stopper conditions to check?
  	 */
  	pkrte = makeNode(RangeTblEntry);
  	pkrte->rtekind = RTE_RELATION;
  	pkrte->relid = RelationGetRelid(pk_rel);
  	pkrte->relkind = pk_rel->rd_rel->relkind;
  	pkrte->requiredPerms = ACL_SELECT;
  
  	fkrte = makeNode(RangeTblEntry);
  	fkrte->rtekind = RTE_RELATION;
  	fkrte->relid = RelationGetRelid(fk_rel);
  	fkrte->relkind = fk_rel->rd_rel->relkind;
  	fkrte->requiredPerms = ACL_SELECT;
  
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		int			attno;
  
  		attno = riinfo->pk_attnums[i] - FirstLowInvalidHeapAttributeNumber;
  		pkrte->selectedCols = bms_add_member(pkrte->selectedCols, attno);
  
  		attno = riinfo->fk_attnums[i] - FirstLowInvalidHeapAttributeNumber;
  		fkrte->selectedCols = bms_add_member(fkrte->selectedCols, attno);
  	}
  
  	if (!ExecCheckRTPerms(list_make2(fkrte, pkrte), false))
  		return false;
  
  	/*----------
  	 * The query string built is:
  	 *	SELECT fk.keycols FROM ONLY relname fk
  	 *	 LEFT OUTER JOIN ONLY pkrelname pk
  	 *	 ON (pk.pkkeycol1=fk.keycol1 [AND ...])
  	 *	 WHERE pk.pkkeycol1 IS NULL AND
  	 * For MATCH SIMPLE:
  	 *	 (fk.keycol1 IS NOT NULL [AND ...])
  	 * For MATCH FULL:
  	 *	 (fk.keycol1 IS NOT NULL [OR ...])
  	 *
  	 * We attach COLLATE clauses to the operators when comparing columns
  	 * that have different collations.
  	 *----------
  	 */
  	initStringInfo(&querybuf);
  	appendStringInfoString(&querybuf, "SELECT ");
  	sep = "";
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		quoteOneName(fkattname,
  					 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  		appendStringInfo(&querybuf, "%sfk.%s", sep, fkattname);
  		sep = ", ";
  	}
  
  	quoteRelationName(pkrelname, pk_rel);
  	quoteRelationName(fkrelname, fk_rel);
  	appendStringInfo(&querybuf,
  					 " FROM ONLY %s fk LEFT OUTER JOIN ONLY %s pk ON",
  					 fkrelname, pkrelname);
  
  	strcpy(pkattname, "pk.");
  	strcpy(fkattname, "fk.");
  	sep = "(";
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		Oid			pk_type = RIAttType(pk_rel, riinfo->pk_attnums[i]);
  		Oid			fk_type = RIAttType(fk_rel, riinfo->fk_attnums[i]);
  		Oid			pk_coll = RIAttCollation(pk_rel, riinfo->pk_attnums[i]);
  		Oid			fk_coll = RIAttCollation(fk_rel, riinfo->fk_attnums[i]);
  
  		quoteOneName(pkattname + 3,
  					 RIAttName(pk_rel, riinfo->pk_attnums[i]));
  		quoteOneName(fkattname + 3,
  					 RIAttName(fk_rel, riinfo->fk_attnums[i]));
  		ri_GenerateQual(&querybuf, sep,
  						pkattname, pk_type,
  						riinfo->pf_eq_oprs[i],
  						fkattname, fk_type);
  		if (pk_coll != fk_coll)
  			ri_GenerateQualCollation(&querybuf, pk_coll);
  		sep = "AND";
  	}
  
  	/*
  	 * It's sufficient to test any one pk attribute for null to detect a join
  	 * failure.
  	 */
  	quoteOneName(pkattname, RIAttName(pk_rel, riinfo->pk_attnums[0]));
  	appendStringInfo(&querybuf, ") WHERE pk.%s IS NULL AND (", pkattname);
  
  	sep = "";
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		quoteOneName(fkattname, RIAttName(fk_rel, riinfo->fk_attnums[i]));
  		appendStringInfo(&querybuf,
  						 "%sfk.%s IS NOT NULL",
  						 sep, fkattname);
  		switch (riinfo->confmatchtype)
  		{
  			case FKCONSTR_MATCH_SIMPLE:
  				sep = " AND ";
  				break;
  			case FKCONSTR_MATCH_FULL:
  				sep = " OR ";
  				break;
  			case FKCONSTR_MATCH_PARTIAL:
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("MATCH PARTIAL not yet implemented")));
  				break;
  			default:
  				elog(ERROR, "unrecognized confmatchtype: %d",
  					 riinfo->confmatchtype);
  				break;
  		}
  	}
  	appendStringInfoChar(&querybuf, ')');
  
  	/*
  	 * Temporarily increase work_mem so that the check query can be executed
  	 * more efficiently.  It seems okay to do this because the query is simple
  	 * enough to not use a multiple of work_mem, and one typically would not
  	 * have many large foreign-key validations happening concurrently.  So
  	 * this seems to meet the criteria for being considered a "maintenance"
  	 * operation, and accordingly we use maintenance_work_mem.
  	 *
  	 * We use the equivalent of a function SET option to allow the setting to
  	 * persist for exactly the duration of the check query.  guc.c also takes
  	 * care of undoing the setting on error.
  	 */
  	save_nestlevel = NewGUCNestLevel();
  
  	snprintf(workmembuf, sizeof(workmembuf), "%d", maintenance_work_mem);
  	(void) set_config_option("work_mem", workmembuf,
  							 PGC_USERSET, PGC_S_SESSION,
  							 GUC_ACTION_SAVE, true, 0);
  
  	if (SPI_connect() != SPI_OK_CONNECT)
  		elog(ERROR, "SPI_connect failed");
  
  	/*
  	 * Generate the plan.  We don't need to cache it, and there are no
  	 * arguments to the plan.
  	 */
  	qplan = SPI_prepare(querybuf.data, 0, NULL);
  
  	if (qplan == NULL)
  		elog(ERROR, "SPI_prepare returned %d for %s",
  			 SPI_result, querybuf.data);
  
  	/*
  	 * Run the plan.  For safety we force a current snapshot to be used. (In
  	 * transaction-snapshot mode, this arguably violates transaction isolation
  	 * rules, but we really haven't got much choice.) We don't need to
  	 * register the snapshot, because SPI_execute_snapshot will see to it. We
  	 * need at most one tuple returned, so pass limit = 1.
  	 */
  	spi_result = SPI_execute_snapshot(qplan,
  									  NULL, NULL,
  									  GetLatestSnapshot(),
  									  InvalidSnapshot,
  									  true, false, 1);
  
  	/* Check result */
  	if (spi_result != SPI_OK_SELECT)
  		elog(ERROR, "SPI_execute_snapshot returned %d", spi_result);
  
  	/* Did we find a tuple violating the constraint? */
  	if (SPI_processed > 0)
  	{
  		HeapTuple	tuple = SPI_tuptable->vals[0];
  		TupleDesc	tupdesc = SPI_tuptable->tupdesc;
  		RI_ConstraintInfo fake_riinfo;
  
  		/*
  		 * The columns to look at in the result tuple are 1..N, not whatever
  		 * they are in the fk_rel.  Hack up riinfo so that the subroutines
  		 * called here will behave properly.
  		 *
  		 * In addition to this, we have to pass the correct tupdesc to
  		 * ri_ReportViolation, overriding its normal habit of using the pk_rel
  		 * or fk_rel's tupdesc.
  		 */
  		memcpy(&fake_riinfo, riinfo, sizeof(RI_ConstraintInfo));
  		for (i = 0; i < fake_riinfo.nkeys; i++)
  			fake_riinfo.fk_attnums[i] = i + 1;
  
  		/*
  		 * If it's MATCH FULL, and there are any nulls in the FK keys,
  		 * complain about that rather than the lack of a match.  MATCH FULL
  		 * disallows partially-null FK rows.
  		 */
  		if (fake_riinfo.confmatchtype == FKCONSTR_MATCH_FULL &&
  			ri_NullCheck(tuple, &fake_riinfo, false) != RI_KEYS_NONE_NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_FOREIGN_KEY_VIOLATION),
  					 errmsg("insert or update on table \"%s\" violates foreign key constraint \"%s\"",
  							RelationGetRelationName(fk_rel),
  							NameStr(fake_riinfo.conname)),
  					 errdetail("MATCH FULL does not allow mixing of null and nonnull key values."),
  					 errtableconstraint(fk_rel,
  										NameStr(fake_riinfo.conname))));
  
  		/*
  		 * We tell ri_ReportViolation we were doing the RI_PLAN_CHECK_LOOKUPPK
  		 * query, which isn't true, but will cause it to use
  		 * fake_riinfo.fk_attnums as we need.
  		 */
  		ri_ReportViolation(&fake_riinfo,
  						   pk_rel, fk_rel,
  						   tuple, tupdesc,
  						   RI_PLAN_CHECK_LOOKUPPK, false);
  	}
  
  	if (SPI_finish() != SPI_OK_FINISH)
  		elog(ERROR, "SPI_finish failed");
  
  	/*
  	 * Restore work_mem.
  	 */
  	AtEOXact_GUC(true, save_nestlevel);
  
  	return true;
  }
  
  
  /* ----------
   * Local functions below
   * ----------
   */
  
  
  /*
   * quoteOneName --- safely quote a single SQL name
   *
   * buffer must be MAX_QUOTED_NAME_LEN long (includes room for \0)
   */
  static void
  quoteOneName(char *buffer, const char *name)
  {
  	/* Rather than trying to be smart, just always quote it. */
  	*buffer++ = '"';
  	while (*name)
  	{
  		if (*name == '"')
  			*buffer++ = '"';
  		*buffer++ = *name++;
  	}
  	*buffer++ = '"';
  	*buffer = '\0';
  }
  
  /*
   * quoteRelationName --- safely quote a fully qualified relation name
   *
   * buffer must be MAX_QUOTED_REL_NAME_LEN long (includes room for \0)
   */
  static void
  quoteRelationName(char *buffer, Relation rel)
  {
  	quoteOneName(buffer, get_namespace_name(RelationGetNamespace(rel)));
  	buffer += strlen(buffer);
  	*buffer++ = '.';
  	quoteOneName(buffer, RelationGetRelationName(rel));
  }
  
  /*
   * ri_GenerateQual --- generate a WHERE clause equating two variables
   *
   * This basically appends " sep leftop op rightop" to buf, adding casts
   * and schema qualification as needed to ensure that the parser will select
   * the operator we specify.  leftop and rightop should be parenthesized
   * if they aren't variables or parameters.
   */
  static void
  ri_GenerateQual(StringInfo buf,
  				const char *sep,
  				const char *leftop, Oid leftoptype,
  				Oid opoid,
  				const char *rightop, Oid rightoptype)
  {
  	appendStringInfo(buf, " %s ", sep);
  	generate_operator_clause(buf, leftop, leftoptype, opoid,
  							 rightop, rightoptype);
  }
  
  /*
   * ri_GenerateQualCollation --- add a COLLATE spec to a WHERE clause
   *
   * At present, we intentionally do not use this function for RI queries that
   * compare a variable to a $n parameter.  Since parameter symbols always have
   * default collation, the effect will be to use the variable's collation.
   * Now that is only strictly correct when testing the referenced column, since
   * the SQL standard specifies that RI comparisons should use the referenced
   * column's collation.  However, so long as all collations have the same
   * notion of equality (which they do, because texteq reduces to bitwise
   * equality), there's no visible semantic impact from using the referencing
   * column's collation when testing it, and this is a good thing to do because
   * it lets us use a normal index on the referencing column.  However, we do
   * have to use this function when directly comparing the referencing and
   * referenced columns, if they are of different collations; else the parser
   * will fail to resolve the collation to use.
   */
  static void
  ri_GenerateQualCollation(StringInfo buf, Oid collation)
  {
  	HeapTuple	tp;
  	Form_pg_collation colltup;
  	char	   *collname;
  	char		onename[MAX_QUOTED_NAME_LEN];
  
  	/* Nothing to do if it's a noncollatable data type */
  	if (!OidIsValid(collation))
  		return;
  
  	tp = SearchSysCache1(COLLOID, ObjectIdGetDatum(collation));
  	if (!HeapTupleIsValid(tp))
  		elog(ERROR, "cache lookup failed for collation %u", collation);
  	colltup = (Form_pg_collation) GETSTRUCT(tp);
  	collname = NameStr(colltup->collname);
  
  	/*
  	 * We qualify the name always, for simplicity and to ensure the query is
  	 * not search-path-dependent.
  	 */
  	quoteOneName(onename, get_namespace_name(colltup->collnamespace));
  	appendStringInfo(buf, " COLLATE %s", onename);
  	quoteOneName(onename, collname);
  	appendStringInfo(buf, ".%s", onename);
  
  	ReleaseSysCache(tp);
  }
  
  /* ----------
   * ri_BuildQueryKey -
   *
   *	Construct a hashtable key for a prepared SPI plan of an FK constraint.
   *
   *		key: output argument, *key is filled in based on the other arguments
   *		riinfo: info from pg_constraint entry
   *		constr_queryno: an internal number identifying the query type
   *			(see RI_PLAN_XXX constants at head of file)
   * ----------
   */
  static void
  ri_BuildQueryKey(RI_QueryKey *key, const RI_ConstraintInfo *riinfo,
  				 int32 constr_queryno)
  {
  	/*
  	 * We assume struct RI_QueryKey contains no padding bytes, else we'd need
  	 * to use memset to clear them.
  	 */
  	key->constr_id = riinfo->constraint_id;
  	key->constr_queryno = constr_queryno;
  }
  
  /*
   * Check that RI trigger function was called in expected context
   */
  static void
  ri_CheckTrigger(FunctionCallInfo fcinfo, const char *funcname, int tgkind)
  {
  	TriggerData *trigdata = (TriggerData *) fcinfo->context;
  
  	if (!CALLED_AS_TRIGGER(fcinfo))
  		ereport(ERROR,
  				(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
  				 errmsg("function \"%s\" was not called by trigger manager", funcname)));
  
  	/*
  	 * Check proper event
  	 */
  	if (!TRIGGER_FIRED_AFTER(trigdata->tg_event) ||
  		!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
  		ereport(ERROR,
  				(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
  			   errmsg("function \"%s\" must be fired AFTER ROW", funcname)));
  
  	switch (tgkind)
  	{
  		case RI_TRIGTYPE_INSERT:
  			if (!TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
  				ereport(ERROR,
  						(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
  						 errmsg("function \"%s\" must be fired for INSERT", funcname)));
  			break;
  		case RI_TRIGTYPE_UPDATE:
  			if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
  				ereport(ERROR,
  						(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
  						 errmsg("function \"%s\" must be fired for UPDATE", funcname)));
  			break;
  		case RI_TRIGTYPE_DELETE:
  			if (!TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
  				ereport(ERROR,
  						(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
  						 errmsg("function \"%s\" must be fired for DELETE", funcname)));
  			break;
  	}
  }
  
  
  /*
   * Fetch the RI_ConstraintInfo struct for the trigger's FK constraint.
   */
  static const RI_ConstraintInfo *
  ri_FetchConstraintInfo(Trigger *trigger, Relation trig_rel, bool rel_is_pk)
  {
  	Oid			constraintOid = trigger->tgconstraint;
  	const RI_ConstraintInfo *riinfo;
  
  	/*
  	 * Check that the FK constraint's OID is available; it might not be if
  	 * we've been invoked via an ordinary trigger or an old-style "constraint
  	 * trigger".
  	 */
  	if (!OidIsValid(constraintOid))
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  		  errmsg("no pg_constraint entry for trigger \"%s\" on table \"%s\"",
  				 trigger->tgname, RelationGetRelationName(trig_rel)),
  				 errhint("Remove this referential integrity trigger and its mates, then do ALTER TABLE ADD CONSTRAINT.")));
  
  	/* Find or create a hashtable entry for the constraint */
  	riinfo = ri_LoadConstraintInfo(constraintOid);
  
  	/* Do some easy cross-checks against the trigger call data */
  	if (rel_is_pk)
  	{
  		if (riinfo->fk_relid != trigger->tgconstrrelid ||
  			riinfo->pk_relid != RelationGetRelid(trig_rel))
  			elog(ERROR, "wrong pg_constraint entry for trigger \"%s\" on table \"%s\"",
  				 trigger->tgname, RelationGetRelationName(trig_rel));
  	}
  	else
  	{
  		if (riinfo->fk_relid != RelationGetRelid(trig_rel) ||
  			riinfo->pk_relid != trigger->tgconstrrelid)
  			elog(ERROR, "wrong pg_constraint entry for trigger \"%s\" on table \"%s\"",
  				 trigger->tgname, RelationGetRelationName(trig_rel));
  	}
  
  	return riinfo;
  }
  
  /*
   * Fetch or create the RI_ConstraintInfo struct for an FK constraint.
   */
  static const RI_ConstraintInfo *
  ri_LoadConstraintInfo(Oid constraintOid)
  {
  	RI_ConstraintInfo *riinfo;
  	bool		found;
  	HeapTuple	tup;
  	Form_pg_constraint conForm;
  	Datum		adatum;
  	bool		isNull;
  	ArrayType  *arr;
  	int			numkeys;
  
  	/*
  	 * On the first call initialize the hashtable
  	 */
  	if (!ri_constraint_cache)
  		ri_InitHashTables();
  
  	/*
  	 * Find or create a hash entry.  If we find a valid one, just return it.
  	 */
  	riinfo = (RI_ConstraintInfo *) hash_search(ri_constraint_cache,
  											   (void *) &constraintOid,
  											   HASH_ENTER, &found);
  	if (!found)
  		riinfo->valid = false;
  	else if (riinfo->valid)
  		return riinfo;
  
  	/*
  	 * Fetch the pg_constraint row so we can fill in the entry.
  	 */
  	tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constraintOid));
  	if (!HeapTupleIsValid(tup)) /* should not happen */
  		elog(ERROR, "cache lookup failed for constraint %u", constraintOid);
  	conForm = (Form_pg_constraint) GETSTRUCT(tup);
  
  	if (conForm->contype != CONSTRAINT_FOREIGN) /* should not happen */
  		elog(ERROR, "constraint %u is not a foreign key constraint",
  			 constraintOid);
  
  	/* And extract data */
  	Assert(riinfo->constraint_id == constraintOid);
  	riinfo->oidHashValue = GetSysCacheHashValue1(CONSTROID,
  											ObjectIdGetDatum(constraintOid));
  	memcpy(&riinfo->conname, &conForm->conname, sizeof(NameData));
  	riinfo->pk_relid = conForm->confrelid;
  	riinfo->fk_relid = conForm->conrelid;
  	riinfo->confupdtype = conForm->confupdtype;
  	riinfo->confdeltype = conForm->confdeltype;
  	riinfo->confmatchtype = conForm->confmatchtype;
  
  	/*
  	 * We expect the arrays to be 1-D arrays of the right types; verify that.
  	 * We don't need to use deconstruct_array() since the array data is just
  	 * going to look like a C array of values.
  	 */
  	adatum = SysCacheGetAttr(CONSTROID, tup,
  							 Anum_pg_constraint_conkey, &isNull);
  	if (isNull)
  		elog(ERROR, "null conkey for constraint %u", constraintOid);
  	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
  	if (ARR_NDIM(arr) != 1 ||
  		ARR_HASNULL(arr) ||
  		ARR_ELEMTYPE(arr) != INT2OID)
  		elog(ERROR, "conkey is not a 1-D smallint array");
  	numkeys = ARR_DIMS(arr)[0];
  	if (numkeys <= 0 || numkeys > RI_MAX_NUMKEYS)
  		elog(ERROR, "foreign key constraint cannot have %d columns", numkeys);
  	riinfo->nkeys = numkeys;
  	memcpy(riinfo->fk_attnums, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
  	if ((Pointer) arr != DatumGetPointer(adatum))
  		pfree(arr);				/* free de-toasted copy, if any */
  
  	adatum = SysCacheGetAttr(CONSTROID, tup,
  							 Anum_pg_constraint_confkey, &isNull);
  	if (isNull)
  		elog(ERROR, "null confkey for constraint %u", constraintOid);
  	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
  	if (ARR_NDIM(arr) != 1 ||
  		ARR_DIMS(arr)[0] != numkeys ||
  		ARR_HASNULL(arr) ||
  		ARR_ELEMTYPE(arr) != INT2OID)
  		elog(ERROR, "confkey is not a 1-D smallint array");
  	memcpy(riinfo->pk_attnums, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
  	if ((Pointer) arr != DatumGetPointer(adatum))
  		pfree(arr);				/* free de-toasted copy, if any */
  
  	adatum = SysCacheGetAttr(CONSTROID, tup,
  							 Anum_pg_constraint_conpfeqop, &isNull);
  	if (isNull)
  		elog(ERROR, "null conpfeqop for constraint %u", constraintOid);
  	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
  	/* see TryReuseForeignKey if you change the test below */
  	if (ARR_NDIM(arr) != 1 ||
  		ARR_DIMS(arr)[0] != numkeys ||
  		ARR_HASNULL(arr) ||
  		ARR_ELEMTYPE(arr) != OIDOID)
  		elog(ERROR, "conpfeqop is not a 1-D Oid array");
  	memcpy(riinfo->pf_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
  	if ((Pointer) arr != DatumGetPointer(adatum))
  		pfree(arr);				/* free de-toasted copy, if any */
  
  	adatum = SysCacheGetAttr(CONSTROID, tup,
  							 Anum_pg_constraint_conppeqop, &isNull);
  	if (isNull)
  		elog(ERROR, "null conppeqop for constraint %u", constraintOid);
  	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
  	if (ARR_NDIM(arr) != 1 ||
  		ARR_DIMS(arr)[0] != numkeys ||
  		ARR_HASNULL(arr) ||
  		ARR_ELEMTYPE(arr) != OIDOID)
  		elog(ERROR, "conppeqop is not a 1-D Oid array");
  	memcpy(riinfo->pp_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
  	if ((Pointer) arr != DatumGetPointer(adatum))
  		pfree(arr);				/* free de-toasted copy, if any */
  
  	adatum = SysCacheGetAttr(CONSTROID, tup,
  							 Anum_pg_constraint_conffeqop, &isNull);
  	if (isNull)
  		elog(ERROR, "null conffeqop for constraint %u", constraintOid);
  	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
  	if (ARR_NDIM(arr) != 1 ||
  		ARR_DIMS(arr)[0] != numkeys ||
  		ARR_HASNULL(arr) ||
  		ARR_ELEMTYPE(arr) != OIDOID)
  		elog(ERROR, "conffeqop is not a 1-D Oid array");
  	memcpy(riinfo->ff_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
  	if ((Pointer) arr != DatumGetPointer(adatum))
  		pfree(arr);				/* free de-toasted copy, if any */
  
  	ReleaseSysCache(tup);
  
  	/*
  	 * For efficient processing of invalidation messages below, we keep a
  	 * doubly-linked list, and a count, of all currently valid entries.
  	 */
  	dlist_push_tail(&ri_constraint_cache_valid_list, &riinfo->valid_link);
  	ri_constraint_cache_valid_count++;
  
  	riinfo->valid = true;
  
  	return riinfo;
  }
  
  /*
   * Callback for pg_constraint inval events
   *
   * While most syscache callbacks just flush all their entries, pg_constraint
   * gets enough update traffic that it's probably worth being smarter.
   * Invalidate any ri_constraint_cache entry associated with the syscache
   * entry with the specified hash value, or all entries if hashvalue == 0.
   *
   * Note: at the time a cache invalidation message is processed there may be
   * active references to the cache.  Because of this we never remove entries
   * from the cache, but only mark them invalid, which is harmless to active
   * uses.  (Any query using an entry should hold a lock sufficient to keep that
   * data from changing under it --- but we may get cache flushes anyway.)
   */
  static void
  InvalidateConstraintCacheCallBack(Datum arg, int cacheid, uint32 hashvalue)
  {
  	dlist_mutable_iter iter;
  
  	Assert(ri_constraint_cache != NULL);
  
  	/*
  	 * If the list of currently valid entries gets excessively large, we mark
  	 * them all invalid so we can empty the list.  This arrangement avoids
  	 * O(N^2) behavior in situations where a session touches many foreign keys
  	 * and also does many ALTER TABLEs, such as a restore from pg_dump.
  	 */
  	if (ri_constraint_cache_valid_count > 1000)
  		hashvalue = 0;			/* pretend it's a cache reset */
  
  	dlist_foreach_modify(iter, &ri_constraint_cache_valid_list)
  	{
  		RI_ConstraintInfo *riinfo = dlist_container(RI_ConstraintInfo,
  													valid_link, iter.cur);
  
  		if (hashvalue == 0 || riinfo->oidHashValue == hashvalue)
  		{
  			riinfo->valid = false;
  			/* Remove invalidated entries from the list, too */
  			dlist_delete(iter.cur);
  			ri_constraint_cache_valid_count--;
  		}
  	}
  }
  
  
  /*
   * Prepare execution plan for a query to enforce an RI restriction
   *
   * If cache_plan is true, the plan is saved into our plan hashtable
   * so that we don't need to plan it again.
   */
  static SPIPlanPtr
  ri_PlanCheck(const char *querystr, int nargs, Oid *argtypes,
  			 RI_QueryKey *qkey, Relation fk_rel, Relation pk_rel,
  			 bool cache_plan)
  {
  	SPIPlanPtr	qplan;
  	Relation	query_rel;
  	Oid			save_userid;
  	int			save_sec_context;
  
  	/*
  	 * Use the query type code to determine whether the query is run against
  	 * the PK or FK table; we'll do the check as that table's owner
  	 */
  	if (qkey->constr_queryno <= RI_PLAN_LAST_ON_PK)
  		query_rel = pk_rel;
  	else
  		query_rel = fk_rel;
  
  	/* Switch to proper UID to perform check as */
  	GetUserIdAndSecContext(&save_userid, &save_sec_context);
  	SetUserIdAndSecContext(RelationGetForm(query_rel)->relowner,
  						   save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
  
  	/* Create the plan */
  	qplan = SPI_prepare(querystr, nargs, argtypes);
  
  	if (qplan == NULL)
  		elog(ERROR, "SPI_prepare returned %d for %s", SPI_result, querystr);
  
  	/* Restore UID and security context */
  	SetUserIdAndSecContext(save_userid, save_sec_context);
  
  	/* Save the plan if requested */
  	if (cache_plan)
  	{
  		SPI_keepplan(qplan);
  		ri_HashPreparedPlan(qkey, qplan);
  	}
  
  	return qplan;
  }
  
  /*
   * Perform a query to enforce an RI restriction
   */
  static bool
  ri_PerformCheck(const RI_ConstraintInfo *riinfo,
  				RI_QueryKey *qkey, SPIPlanPtr qplan,
  				Relation fk_rel, Relation pk_rel,
  				HeapTuple old_tuple, HeapTuple new_tuple,
  				bool detectNewRows, int expect_OK)
  {
  	Relation	query_rel,
  				source_rel;
  	bool		source_is_pk;
  	Snapshot	test_snapshot;
  	Snapshot	crosscheck_snapshot;
  	int			limit;
  	int			spi_result;
  	Oid			save_userid;
  	int			save_sec_context;
  	Datum		vals[RI_MAX_NUMKEYS * 2];
  	char		nulls[RI_MAX_NUMKEYS * 2];
  
  	/*
  	 * Use the query type code to determine whether the query is run against
  	 * the PK or FK table; we'll do the check as that table's owner
  	 */
  	if (qkey->constr_queryno <= RI_PLAN_LAST_ON_PK)
  		query_rel = pk_rel;
  	else
  		query_rel = fk_rel;
  
  	/*
  	 * The values for the query are taken from the table on which the trigger
  	 * is called - it is normally the other one with respect to query_rel. An
  	 * exception is ri_Check_Pk_Match(), which uses the PK table for both (and
  	 * sets queryno to RI_PLAN_CHECK_LOOKUPPK_FROM_PK).  We might eventually
  	 * need some less klugy way to determine this.
  	 */
  	if (qkey->constr_queryno == RI_PLAN_CHECK_LOOKUPPK)
  	{
  		source_rel = fk_rel;
  		source_is_pk = false;
  	}
  	else
  	{
  		source_rel = pk_rel;
  		source_is_pk = true;
  	}
  
  	/* Extract the parameters to be passed into the query */
  	if (new_tuple)
  	{
  		ri_ExtractValues(source_rel, new_tuple, riinfo, source_is_pk,
  						 vals, nulls);
  		if (old_tuple)
  			ri_ExtractValues(source_rel, old_tuple, riinfo, source_is_pk,
  							 vals + riinfo->nkeys, nulls + riinfo->nkeys);
  	}
  	else
  	{
  		ri_ExtractValues(source_rel, old_tuple, riinfo, source_is_pk,
  						 vals, nulls);
  	}
  
  	/*
  	 * In READ COMMITTED mode, we just need to use an up-to-date regular
  	 * snapshot, and we will see all rows that could be interesting. But in
  	 * transaction-snapshot mode, we can't change the transaction snapshot. If
  	 * the caller passes detectNewRows == false then it's okay to do the query
  	 * with the transaction snapshot; otherwise we use a current snapshot, and
  	 * tell the executor to error out if it finds any rows under the current
  	 * snapshot that wouldn't be visible per the transaction snapshot.  Note
  	 * that SPI_execute_snapshot will register the snapshots, so we don't need
  	 * to bother here.
  	 */
  	if (IsolationUsesXactSnapshot() && detectNewRows)
  	{
  		CommandCounterIncrement();		/* be sure all my own work is visible */
  		test_snapshot = GetLatestSnapshot();
  		crosscheck_snapshot = GetTransactionSnapshot();
  	}
  	else
  	{
  		/* the default SPI behavior is okay */
  		test_snapshot = InvalidSnapshot;
  		crosscheck_snapshot = InvalidSnapshot;
  	}
  
  	/*
  	 * If this is a select query (e.g., for a 'no action' or 'restrict'
  	 * trigger), we only need to see if there is a single row in the table,
  	 * matching the key.  Otherwise, limit = 0 - because we want the query to
  	 * affect ALL the matching rows.
  	 */
  	limit = (expect_OK == SPI_OK_SELECT) ? 1 : 0;
  
  	/* Switch to proper UID to perform check as */
  	GetUserIdAndSecContext(&save_userid, &save_sec_context);
  	SetUserIdAndSecContext(RelationGetForm(query_rel)->relowner,
  						   save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
  
  	/* Finally we can run the query. */
  	spi_result = SPI_execute_snapshot(qplan,
  									  vals, nulls,
  									  test_snapshot, crosscheck_snapshot,
  									  false, false, limit);
  
  	/* Restore UID and security context */
  	SetUserIdAndSecContext(save_userid, save_sec_context);
  
  	/* Check result */
  	if (spi_result < 0)
  		elog(ERROR, "SPI_execute_snapshot returned %d", spi_result);
  
  	if (expect_OK >= 0 && spi_result != expect_OK)
  		ri_ReportViolation(riinfo,
  						   pk_rel, fk_rel,
  						   new_tuple ? new_tuple : old_tuple,
  						   NULL,
  						   qkey->constr_queryno, true);
  
  	/* XXX wouldn't it be clearer to do this part at the caller? */
  	if (qkey->constr_queryno != RI_PLAN_CHECK_LOOKUPPK_FROM_PK &&
  		expect_OK == SPI_OK_SELECT &&
  	(SPI_processed == 0) == (qkey->constr_queryno == RI_PLAN_CHECK_LOOKUPPK))
  		ri_ReportViolation(riinfo,
  						   pk_rel, fk_rel,
  						   new_tuple ? new_tuple : old_tuple,
  						   NULL,
  						   qkey->constr_queryno, false);
  
  	return SPI_processed != 0;
  }
  
  /*
   * Extract fields from a tuple into Datum/nulls arrays
   */
  static void
  ri_ExtractValues(Relation rel, HeapTuple tup,
  				 const RI_ConstraintInfo *riinfo, bool rel_is_pk,
  				 Datum *vals, char *nulls)
  {
  	TupleDesc	tupdesc = rel->rd_att;
  	const int16 *attnums;
  	int			i;
  	bool		isnull;
  
  	if (rel_is_pk)
  		attnums = riinfo->pk_attnums;
  	else
  		attnums = riinfo->fk_attnums;
  
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		vals[i] = heap_getattr(tup, attnums[i], tupdesc,
  							   &isnull);
  		nulls[i] = isnull ? 'n' : ' ';
  	}
  }
  
  /*
   * Produce an error report
   *
   * If the failed constraint was on insert/update to the FK table,
   * we want the key names and values extracted from there, and the error
   * message to look like 'key blah is not present in PK'.
   * Otherwise, the attr names and values come from the PK table and the
   * message looks like 'key blah is still referenced from FK'.
   */
  static void
  ri_ReportViolation(const RI_ConstraintInfo *riinfo,
  				   Relation pk_rel, Relation fk_rel,
  				   HeapTuple violator, TupleDesc tupdesc,
  				   int queryno, bool spi_err)
  {
  	StringInfoData key_names;
  	StringInfoData key_values;
  	bool		onfk;
  	const int16 *attnums;
  	int			idx;
  	Oid			rel_oid;
  	AclResult	aclresult;
  	bool		has_perm = true;
  
  	if (spi_err)
  		ereport(ERROR,
  				(errcode(ERRCODE_INTERNAL_ERROR),
  				 errmsg("referential integrity query on \"%s\" from constraint \"%s\" on \"%s\" gave unexpected result",
  						RelationGetRelationName(pk_rel),
  						NameStr(riinfo->conname),
  						RelationGetRelationName(fk_rel)),
  				 errhint("This is most likely due to a rule having rewritten the query.")));
  
  	/*
  	 * Determine which relation to complain about.  If tupdesc wasn't passed
  	 * by caller, assume the violator tuple came from there.
  	 */
  	onfk = (queryno == RI_PLAN_CHECK_LOOKUPPK);
  	if (onfk)
  	{
  		attnums = riinfo->fk_attnums;
  		rel_oid = fk_rel->rd_id;
  		if (tupdesc == NULL)
  			tupdesc = fk_rel->rd_att;
  	}
  	else
  	{
  		attnums = riinfo->pk_attnums;
  		rel_oid = pk_rel->rd_id;
  		if (tupdesc == NULL)
  			tupdesc = pk_rel->rd_att;
  	}
  
  	/*
  	 * Check permissions- if the user does not have access to view the data in
  	 * any of the key columns then we don't include the errdetail() below.
  	 *
  	 * Check table-level permissions first and, failing that, column-level
  	 * privileges.
  	 */
  	aclresult = pg_class_aclcheck(rel_oid, GetUserId(), ACL_SELECT);
  	if (aclresult != ACLCHECK_OK)
  	{
  		/* Try for column-level permissions */
  		for (idx = 0; idx < riinfo->nkeys; idx++)
  		{
  			aclresult = pg_attribute_aclcheck(rel_oid, attnums[idx],
  											  GetUserId(),
  											  ACL_SELECT);
  
  			/* No access to the key */
  			if (aclresult != ACLCHECK_OK)
  			{
  				has_perm = false;
  				break;
  			}
  		}
  	}
  
  	if (has_perm)
  	{
  		/* Get printable versions of the keys involved */
  		initStringInfo(&key_names);
  		initStringInfo(&key_values);
  		for (idx = 0; idx < riinfo->nkeys; idx++)
  		{
  			int			fnum = attnums[idx];
  			char	   *name,
  				   *val;
  
  			name = SPI_fname(tupdesc, fnum);
  			val = SPI_getvalue(violator, tupdesc, fnum);
  			if (!val)
  				val = "null";
  
  			if (idx > 0)
  			{
  				appendStringInfoString(&key_names, ", ");
  				appendStringInfoString(&key_values, ", ");
  			}
  			appendStringInfoString(&key_names, name);
  			appendStringInfoString(&key_values, val);
  		}
  	}
  
  	if (onfk)
  		ereport(ERROR,
  				(errcode(ERRCODE_FOREIGN_KEY_VIOLATION),
  				 errmsg("insert or update on table \"%s\" violates foreign key constraint \"%s\"",
  						RelationGetRelationName(fk_rel),
  						NameStr(riinfo->conname)),
  				 has_perm ?
  					 errdetail("Key (%s)=(%s) is not present in table \"%s\".",
  							   key_names.data, key_values.data,
  							   RelationGetRelationName(pk_rel)) :
  					 errdetail("Key is not present in table \"%s\".",
  							   RelationGetRelationName(pk_rel)),
  				 errtableconstraint(fk_rel, NameStr(riinfo->conname))));
  	else
  		ereport(ERROR,
  				(errcode(ERRCODE_FOREIGN_KEY_VIOLATION),
  				 errmsg("update or delete on table \"%s\" violates foreign key constraint \"%s\" on table \"%s\"",
  						RelationGetRelationName(pk_rel),
  						NameStr(riinfo->conname),
  						RelationGetRelationName(fk_rel)),
  				 has_perm ?
  			errdetail("Key (%s)=(%s) is still referenced from table \"%s\".",
  					  key_names.data, key_values.data,
  					  RelationGetRelationName(fk_rel)) :
  					errdetail("Key is still referenced from table \"%s\".",
  					  RelationGetRelationName(fk_rel)),
  				 errtableconstraint(fk_rel, NameStr(riinfo->conname))));
  }
  
  
  /* ----------
   * ri_NullCheck -
   *
   *	Determine the NULL state of all key values in a tuple
   *
   *	Returns one of RI_KEYS_ALL_NULL, RI_KEYS_NONE_NULL or RI_KEYS_SOME_NULL.
   * ----------
   */
  static int
  ri_NullCheck(HeapTuple tup,
  			 const RI_ConstraintInfo *riinfo, bool rel_is_pk)
  {
  	const int16 *attnums;
  	int			i;
  	bool		allnull = true;
  	bool		nonenull = true;
  
  	if (rel_is_pk)
  		attnums = riinfo->pk_attnums;
  	else
  		attnums = riinfo->fk_attnums;
  
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		if (heap_attisnull(tup, attnums[i]))
  			nonenull = false;
  		else
  			allnull = false;
  	}
  
  	if (allnull)
  		return RI_KEYS_ALL_NULL;
  
  	if (nonenull)
  		return RI_KEYS_NONE_NULL;
  
  	return RI_KEYS_SOME_NULL;
  }
  
  
  /* ----------
   * ri_InitHashTables -
   *
   *	Initialize our internal hash tables.
   * ----------
   */
  static void
  ri_InitHashTables(void)
  {
  	HASHCTL		ctl;
  
  	memset(&ctl, 0, sizeof(ctl));
  	ctl.keysize = sizeof(Oid);
  	ctl.entrysize = sizeof(RI_ConstraintInfo);
  	ctl.hash = oid_hash;
  	ri_constraint_cache = hash_create("RI constraint cache",
  									  RI_INIT_CONSTRAINTHASHSIZE,
  									  &ctl, HASH_ELEM | HASH_FUNCTION);
  
  	/* Arrange to flush cache on pg_constraint changes */
  	CacheRegisterSyscacheCallback(CONSTROID,
  								  InvalidateConstraintCacheCallBack,
  								  (Datum) 0);
  
  	memset(&ctl, 0, sizeof(ctl));
  	ctl.keysize = sizeof(RI_QueryKey);
  	ctl.entrysize = sizeof(RI_QueryHashEntry);
  	ctl.hash = tag_hash;
  	ri_query_cache = hash_create("RI query cache",
  								 RI_INIT_QUERYHASHSIZE,
  								 &ctl, HASH_ELEM | HASH_FUNCTION);
  
  	memset(&ctl, 0, sizeof(ctl));
  	ctl.keysize = sizeof(RI_CompareKey);
  	ctl.entrysize = sizeof(RI_CompareHashEntry);
  	ctl.hash = tag_hash;
  	ri_compare_cache = hash_create("RI compare cache",
  								   RI_INIT_QUERYHASHSIZE,
  								   &ctl, HASH_ELEM | HASH_FUNCTION);
  }
  
  
  /* ----------
   * ri_FetchPreparedPlan -
   *
   *	Lookup for a query key in our private hash table of prepared
   *	and saved SPI execution plans. Return the plan if found or NULL.
   * ----------
   */
  static SPIPlanPtr
  ri_FetchPreparedPlan(RI_QueryKey *key)
  {
  	RI_QueryHashEntry *entry;
  	SPIPlanPtr	plan;
  
  	/*
  	 * On the first call initialize the hashtable
  	 */
  	if (!ri_query_cache)
  		ri_InitHashTables();
  
  	/*
  	 * Lookup for the key
  	 */
  	entry = (RI_QueryHashEntry *) hash_search(ri_query_cache,
  											  (void *) key,
  											  HASH_FIND, NULL);
  	if (entry == NULL)
  		return NULL;
  
  	/*
  	 * Check whether the plan is still valid.  If it isn't, we don't want to
  	 * simply rely on plancache.c to regenerate it; rather we should start
  	 * from scratch and rebuild the query text too.  This is to cover cases
  	 * such as table/column renames.  We depend on the plancache machinery to
  	 * detect possible invalidations, though.
  	 *
  	 * CAUTION: this check is only trustworthy if the caller has already
  	 * locked both FK and PK rels.
  	 */
  	plan = entry->plan;
  	if (plan && SPI_plan_is_valid(plan))
  		return plan;
  
  	/*
  	 * Otherwise we might as well flush the cached plan now, to free a little
  	 * memory space before we make a new one.
  	 */
  	entry->plan = NULL;
  	if (plan)
  		SPI_freeplan(plan);
  
  	return NULL;
  }
  
  
  /* ----------
   * ri_HashPreparedPlan -
   *
   *	Add another plan to our private SPI query plan hashtable.
   * ----------
   */
  static void
  ri_HashPreparedPlan(RI_QueryKey *key, SPIPlanPtr plan)
  {
  	RI_QueryHashEntry *entry;
  	bool		found;
  
  	/*
  	 * On the first call initialize the hashtable
  	 */
  	if (!ri_query_cache)
  		ri_InitHashTables();
  
  	/*
  	 * Add the new plan.  We might be overwriting an entry previously found
  	 * invalid by ri_FetchPreparedPlan.
  	 */
  	entry = (RI_QueryHashEntry *) hash_search(ri_query_cache,
  											  (void *) key,
  											  HASH_ENTER, &found);
  	Assert(!found || entry->plan == NULL);
  	entry->plan = plan;
  }
  
  
  /* ----------
   * ri_KeysEqual -
   *
   *	Check if all key values in OLD and NEW are equal.
   *
   *	Note: at some point we might wish to redefine this as checking for
   *	"IS NOT DISTINCT" rather than "=", that is, allow two nulls to be
   *	considered equal.  Currently there is no need since all callers have
   *	previously found at least one of the rows to contain no nulls.
   * ----------
   */
  static bool
  ri_KeysEqual(Relation rel, HeapTuple oldtup, HeapTuple newtup,
  			 const RI_ConstraintInfo *riinfo, bool rel_is_pk)
  {
  	TupleDesc	tupdesc = RelationGetDescr(rel);
  	const int16 *attnums;
  	const Oid  *eq_oprs;
  	int			i;
  
  	if (rel_is_pk)
  	{
  		attnums = riinfo->pk_attnums;
  		eq_oprs = riinfo->pp_eq_oprs;
  	}
  	else
  	{
  		attnums = riinfo->fk_attnums;
  		eq_oprs = riinfo->ff_eq_oprs;
  	}
  
  	for (i = 0; i < riinfo->nkeys; i++)
  	{
  		Datum		oldvalue;
  		Datum		newvalue;
  		bool		isnull;
  
  		/*
  		 * Get one attribute's oldvalue. If it is NULL - they're not equal.
  		 */
  		oldvalue = heap_getattr(oldtup, attnums[i], tupdesc, &isnull);
  		if (isnull)
  			return false;
  
  		/*
  		 * Get one attribute's newvalue. If it is NULL - they're not equal.
  		 */
  		newvalue = heap_getattr(newtup, attnums[i], tupdesc, &isnull);
  		if (isnull)
  			return false;
  
  		/*
  		 * Compare them with the appropriate equality operator.
  		 */
  		if (!ri_AttributesEqual(eq_oprs[i], RIAttType(rel, attnums[i]),
  								oldvalue, newvalue))
  			return false;
  	}
  
  	return true;
  }
  
  
  /* ----------
   * ri_AttributesEqual -
   *
   *	Call the appropriate equality comparison operator for two values.
   *
   *	NB: we have already checked that neither value is null.
   * ----------
   */
  static bool
  ri_AttributesEqual(Oid eq_opr, Oid typeid,
  				   Datum oldvalue, Datum newvalue)
  {
  	RI_CompareHashEntry *entry = ri_HashCompareOp(eq_opr, typeid);
  
  	/* Do we need to cast the values? */
  	if (OidIsValid(entry->cast_func_finfo.fn_oid))
  	{
  		oldvalue = FunctionCall3(&entry->cast_func_finfo,
  								 oldvalue,
  								 Int32GetDatum(-1),		/* typmod */
  								 BoolGetDatum(false));	/* implicit coercion */
  		newvalue = FunctionCall3(&entry->cast_func_finfo,
  								 newvalue,
  								 Int32GetDatum(-1),		/* typmod */
  								 BoolGetDatum(false));	/* implicit coercion */
  	}
  
  	/*
  	 * Apply the comparison operator.  We assume it doesn't care about
  	 * collations.
  	 */
  	return DatumGetBool(FunctionCall2(&entry->eq_opr_finfo,
  									  oldvalue, newvalue));
  }
  
  /* ----------
   * ri_HashCompareOp -
   *
   *	See if we know how to compare two values, and create a new hash entry
   *	if not.
   * ----------
   */
  static RI_CompareHashEntry *
  ri_HashCompareOp(Oid eq_opr, Oid typeid)
  {
  	RI_CompareKey key;
  	RI_CompareHashEntry *entry;
  	bool		found;
  
  	/*
  	 * On the first call initialize the hashtable
  	 */
  	if (!ri_compare_cache)
  		ri_InitHashTables();
  
  	/*
  	 * Find or create a hash entry.  Note we're assuming RI_CompareKey
  	 * contains no struct padding.
  	 */
  	key.eq_opr = eq_opr;
  	key.typeid = typeid;
  	entry = (RI_CompareHashEntry *) hash_search(ri_compare_cache,
  												(void *) &key,
  												HASH_ENTER, &found);
  	if (!found)
  		entry->valid = false;
  
  	/*
  	 * If not already initialized, do so.  Since we'll keep this hash entry
  	 * for the life of the backend, put any subsidiary info for the function
  	 * cache structs into TopMemoryContext.
  	 */
  	if (!entry->valid)
  	{
  		Oid			lefttype,
  					righttype,
  					castfunc;
  		CoercionPathType pathtype;
  
  		/* We always need to know how to call the equality operator */
  		fmgr_info_cxt(get_opcode(eq_opr), &entry->eq_opr_finfo,
  					  TopMemoryContext);
  
  		/*
  		 * If we chose to use a cast from FK to PK type, we may have to apply
  		 * the cast function to get to the operator's input type.
  		 *
  		 * XXX eventually it would be good to support array-coercion cases
  		 * here and in ri_AttributesEqual().  At the moment there is no point
  		 * because cases involving nonidentical array types will be rejected
  		 * at constraint creation time.
  		 *
  		 * XXX perhaps also consider supporting CoerceViaIO?  No need at the
  		 * moment since that will never be generated for implicit coercions.
  		 */
  		op_input_types(eq_opr, &lefttype, &righttype);
  		Assert(lefttype == righttype);
  		if (typeid == lefttype)
  			castfunc = InvalidOid;		/* simplest case */
  		else
  		{
  			pathtype = find_coercion_pathway(lefttype, typeid,
  											 COERCION_IMPLICIT,
  											 &castfunc);
  			if (pathtype != COERCION_PATH_FUNC &&
  				pathtype != COERCION_PATH_RELABELTYPE)
  			{
  				/*
  				 * The declared input type of the eq_opr might be a
  				 * polymorphic type such as ANYARRAY or ANYENUM, or other
  				 * special cases such as RECORD; find_coercion_pathway
  				 * currently doesn't subsume these special cases.
  				 */
  				if (!IsBinaryCoercible(typeid, lefttype))
  					elog(ERROR, "no conversion function from %s to %s",
  						 format_type_be(typeid),
  						 format_type_be(lefttype));
  			}
  		}
  		if (OidIsValid(castfunc))
  			fmgr_info_cxt(castfunc, &entry->cast_func_finfo,
  						  TopMemoryContext);
  		else
  			entry->cast_func_finfo.fn_oid = InvalidOid;
  		entry->valid = true;
  	}
  
  	return entry;
  }
  
  
  /*
   * Given a trigger function OID, determine whether it is an RI trigger,
   * and if so whether it is attached to PK or FK relation.
   */
  int
  RI_FKey_trigger_type(Oid tgfoid)
  {
  	switch (tgfoid)
  	{
  		case F_RI_FKEY_CASCADE_DEL:
  		case F_RI_FKEY_CASCADE_UPD:
  		case F_RI_FKEY_RESTRICT_DEL:
  		case F_RI_FKEY_RESTRICT_UPD:
  		case F_RI_FKEY_SETNULL_DEL:
  		case F_RI_FKEY_SETNULL_UPD:
  		case F_RI_FKEY_SETDEFAULT_DEL:
  		case F_RI_FKEY_SETDEFAULT_UPD:
  		case F_RI_FKEY_NOACTION_DEL:
  		case F_RI_FKEY_NOACTION_UPD:
  			return RI_TRIGGER_PK;
  
  		case F_RI_FKEY_CHECK_INS:
  		case F_RI_FKEY_CHECK_UPD:
  			return RI_TRIGGER_FK;
  	}
  
  	return RI_TRIGGER_NONE;
  }
  