text: /*-------------------------------------------------------------------------
   *
   * toasting.c
   *	  This file contains routines to support creation of toast tables
   *
   *
   * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
   *	  src/backend/catalog/toasting.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/heapam.h"
  #include "access/toast_compression.h"
  #include "access/xact.h"
  #include "catalog/binary_upgrade.h"
  #include "catalog/catalog.h"
  #include "catalog/dependency.h"
  #include "catalog/heap.h"
  #include "catalog/index.h"
  #include "catalog/namespace.h"
  #include "catalog/pg_am.h"
  #include "catalog/pg_namespace.h"
  #include "catalog/pg_opclass.h"
  #include "catalog/pg_type.h"
  #include "catalog/toasting.h"
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "storage/lock.h"
  #include "utils/builtins.h"
  #include "utils/rel.h"
  #include "utils/syscache.h"
  
  static void CheckAndCreateToastTable(Oid relOid, Datum reloptions,
  									 LOCKMODE lockmode, bool check,
  									 Oid OIDOldToast);
  static bool create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
  							   Datum reloptions, LOCKMODE lockmode, bool check,
  							   Oid OIDOldToast);
  static bool needs_toast_table(Relation rel);
  
  
  /*
   * CreateToastTable variants
   *		If the table needs a toast table, and doesn't already have one,
   *		then create a toast table for it.
   *
   * reloptions for the toast table can be passed, too.  Pass (Datum) 0
   * for default reloptions.
   *
   * We expect the caller to have verified that the relation is a table and have
   * already done any necessary permission checks.  Callers expect this function
   * to end with CommandCounterIncrement if it makes any changes.
   */
  void
  AlterTableCreateToastTable(Oid relOid, Datum reloptions, LOCKMODE lockmode)
  {
  	CheckAndCreateToastTable(relOid, reloptions, lockmode, true, InvalidOid);
  }
  
  void
  NewHeapCreateToastTable(Oid relOid, Datum reloptions, LOCKMODE lockmode,
  						Oid OIDOldToast)
  {
  	CheckAndCreateToastTable(relOid, reloptions, lockmode, false, OIDOldToast);
  }
  
  void
  NewRelationCreateToastTable(Oid relOid, Datum reloptions)
  {
  	CheckAndCreateToastTable(relOid, reloptions, AccessExclusiveLock, false,
  							 InvalidOid);
  }
  
  static void
  CheckAndCreateToastTable(Oid relOid, Datum reloptions, LOCKMODE lockmode,
  						 bool check, Oid OIDOldToast)
  {
  	Relation	rel;
  
  	rel = table_open(relOid, lockmode);
  
  	/* create_toast_table does all the work */
  	(void) create_toast_table(rel, InvalidOid, InvalidOid, reloptions, lockmode,
  							  check, OIDOldToast);
  
  	table_close(rel, NoLock);
  }
  
  /*
   * Create a toast table during bootstrap
   *
   * Here we need to prespecify the OIDs of the toast table and its index
   */
  void
  BootstrapToastTable(char *relName, Oid toastOid, Oid toastIndexOid)
  {
  	Relation	rel;
  
  	rel = table_openrv(makeRangeVar(NULL, relName, -1), AccessExclusiveLock);
  
  	if (rel->rd_rel->relkind != RELKIND_RELATION &&
  		rel->rd_rel->relkind != RELKIND_MATVIEW)
  		elog(ERROR, "\"%s\" is not a table or materialized view",
  			 relName);
  
  	/* create_toast_table does all the work */
  	if (!create_toast_table(rel, toastOid, toastIndexOid, (Datum) 0,
  							AccessExclusiveLock, false, InvalidOid))
  		elog(ERROR, "\"%s\" does not require a toast table",
  			 relName);
  
  	table_close(rel, NoLock);
  }
  
  
  /*
   * create_toast_table --- internal workhorse
   *
   * rel is already opened and locked
   * toastOid and toastIndexOid are normally InvalidOid, but during
   * bootstrap they can be nonzero to specify hand-assigned OIDs
   */
  static bool
  create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
  				   Datum reloptions, LOCKMODE lockmode, bool check,
  				   Oid OIDOldToast)
  {
  	Oid			relOid = RelationGetRelid(rel);
  	HeapTuple	reltup;
  	TupleDesc	tupdesc;
  	bool		shared_relation;
  	bool		mapped_relation;
  	Relation	toast_rel;
  	Relation	class_rel;
  	Oid			toast_relid;
  	Oid			namespaceid;
  	char		toast_relname[NAMEDATALEN];
  	char		toast_idxname[NAMEDATALEN];
  	IndexInfo  *indexInfo;
  	Oid			collationObjectId[2];
  	Oid			classObjectId[2];
  	int16		coloptions[2];
  	ObjectAddress baseobject,
  				toastobject;
  
  	/*
  	 * Is it already toasted?
  	 */
  	if (rel->rd_rel->reltoastrelid != InvalidOid)
  		return false;
  
  	/*
  	 * Check to see whether the table actually needs a TOAST table.
  	 */
  	if (!IsBinaryUpgrade)
  	{
  		/* Normal mode, normal check */
  		if (!needs_toast_table(rel))
  			return false;
  	}
  	else
  	{
  		/*
  		 * In binary-upgrade mode, create a TOAST table if and only if
  		 * pg_upgrade told us to (ie, a TOAST table OID has been provided).
  		 *
  		 * This indicates that the old cluster had a TOAST table for the
  		 * current table.  We must create a TOAST table to receive the old
  		 * TOAST file, even if the table seems not to need one.
  		 *
  		 * Contrariwise, if the old cluster did not have a TOAST table, we
  		 * should be able to get along without one even if the new version's
  		 * needs_toast_table rules suggest we should have one.  There is a lot
  		 * of daylight between where we will create a TOAST table and where
  		 * one is really necessary to avoid failures, so small cross-version
  		 * differences in the when-to-create heuristic shouldn't be a problem.
  		 * If we tried to create a TOAST table anyway, we would have the
  		 * problem that it might take up an OID that will conflict with some
  		 * old-cluster table we haven't seen yet.
  		 */
  		if (!OidIsValid(binary_upgrade_next_toast_pg_class_oid))
  			return false;
  	}
  
  	/*
  	 * If requested check lockmode is sufficient. This is a cross check in
  	 * case of errors or conflicting decisions in earlier code.
  	 */
  	if (check && lockmode != AccessExclusiveLock)
  		elog(ERROR, "AccessExclusiveLock required to add toast table.");
  
  	/*
  	 * Create the toast table and its index
  	 */
  	snprintf(toast_relname, sizeof(toast_relname),
  			 "pg_toast_%u", relOid);
  	snprintf(toast_idxname, sizeof(toast_idxname),
  			 "pg_toast_%u_index", relOid);
  
  	/* this is pretty painful...  need a tuple descriptor */
  	tupdesc = CreateTemplateTupleDesc(3);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 1,
  					   "chunk_id",
  					   OIDOID,
  					   -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 2,
  					   "chunk_seq",
  					   INT4OID,
  					   -1, 0);
  	TupleDescInitEntry(tupdesc, (AttrNumber) 3,
  					   "chunk_data",
  					   BYTEAOID,
  					   -1, 0);
  
  	/*
  	 * Ensure that the toast table doesn't itself get toasted, or we'll be
  	 * toast :-(.  This is essential for chunk_data because type bytea is
  	 * toastable; hit the other two just to be sure.
  	 */
  	TupleDescAttr(tupdesc, 0)->attstorage = TYPSTORAGE_PLAIN;
  	TupleDescAttr(tupdesc, 1)->attstorage = TYPSTORAGE_PLAIN;
  	TupleDescAttr(tupdesc, 2)->attstorage = TYPSTORAGE_PLAIN;
  
  	/* Toast field should not be compressed */
  	TupleDescAttr(tupdesc, 0)->attcompression = InvalidCompressionMethod;
  	TupleDescAttr(tupdesc, 1)->attcompression = InvalidCompressionMethod;
  	TupleDescAttr(tupdesc, 2)->attcompression = InvalidCompressionMethod;
  
  	/*
  	 * Toast tables for regular relations go in pg_toast; those for temp
  	 * relations go into the per-backend temp-toast-table namespace.
  	 */
  	if (isTempOrTempToastNamespace(rel->rd_rel->relnamespace))
  		namespaceid = GetTempToastNamespace();
  	else
  		namespaceid = PG_TOAST_NAMESPACE;
  
  	/* Toast table is shared if and only if its parent is. */
  	shared_relation = rel->rd_rel->relisshared;
  
  	/* It's mapped if and only if its parent is, too */
  	mapped_relation = RelationIsMapped(rel);
  
  	toast_relid = heap_create_with_catalog(toast_relname,
  										   namespaceid,
  										   rel->rd_rel->reltablespace,
  										   toastOid,
  										   InvalidOid,
  										   InvalidOid,
  										   rel->rd_rel->relowner,
  										   table_relation_toast_am(rel),
  										   tupdesc,
  										   NIL,
  										   RELKIND_TOASTVALUE,
  										   rel->rd_rel->relpersistence,
  										   shared_relation,
  										   mapped_relation,
  										   ONCOMMIT_NOOP,
  										   reloptions,
  										   false,
  										   true,
  										   true,
  										   OIDOldToast,
  										   NULL,
  										   NON_PACKAGE_MEMBER);
  	Assert(toast_relid != InvalidOid);
  
  	/* make the toast relation visible, else table_open will fail */
  	CommandCounterIncrement();
  
  	/* ShareLock is not really needed here, but take it anyway */
  	toast_rel = table_open(toast_relid, ShareLock);
  
  	/*
  	 * Create unique index on chunk_id, chunk_seq.
  	 *
  	 * NOTE: the normal TOAST access routines could actually function with a
  	 * single-column index on chunk_id only. However, the slice access
  	 * routines use both columns for faster access to an individual chunk. In
  	 * addition, we want it to be unique as a check against the possibility of
  	 * duplicate TOAST chunk OIDs. The index might also be a little more
  	 * efficient this way, since btree isn't all that happy with large numbers
  	 * of equal keys.
  	 */
  
  	indexInfo = makeNode(IndexInfo);
  	indexInfo->ii_NumIndexAttrs = 2;
  	indexInfo->ii_NumIndexKeyAttrs = 2;
  	indexInfo->ii_IndexAttrNumbers[0] = 1;
  	indexInfo->ii_IndexAttrNumbers[1] = 2;
  	indexInfo->ii_Expressions = NIL;
  	indexInfo->ii_ExpressionsState = NIL;
  	indexInfo->ii_Predicate = NIL;
  	indexInfo->ii_PredicateState = NULL;
  	indexInfo->ii_ExclusionOps = NULL;
  	indexInfo->ii_ExclusionProcs = NULL;
  	indexInfo->ii_ExclusionStrats = NULL;
  	indexInfo->ii_OpclassOptions = NULL;
  	indexInfo->ii_Unique = true;
  	indexInfo->ii_NullsNotDistinct = false;
  	indexInfo->ii_ReadyForInserts = true;
  	indexInfo->ii_CheckedUnchanged = false;
  	indexInfo->ii_IndexUnchanged = false;
  	indexInfo->ii_Concurrent = false;
  	indexInfo->ii_BrokenHotChain = false;
  	indexInfo->ii_ParallelWorkers = 0;
  	indexInfo->ii_Am = BTREE_AM_OID;
  	indexInfo->ii_AmCache = NULL;
  	indexInfo->ii_Context = CurrentMemoryContext;
  
  	collationObjectId[0] = InvalidOid;
  	collationObjectId[1] = InvalidOid;
  
  	classObjectId[0] = OID_BTREE_OPS_OID;
  	classObjectId[1] = INT4_BTREE_OPS_OID;
  
  	coloptions[0] = 0;
  	coloptions[1] = 0;
  
  	index_create(toast_rel, toast_idxname, toastIndexOid, InvalidOid,
  				 InvalidOid, InvalidOid,
  				 indexInfo,
  				 list_make2("chunk_id", "chunk_seq"),
  				 BTREE_AM_OID,
  				 rel->rd_rel->reltablespace,
  				 collationObjectId, classObjectId, coloptions, (Datum) 0,
  				 INDEX_CREATE_IS_PRIMARY, 0, true, true, NULL);
  
  	table_close(toast_rel, NoLock);
  
  	/*
  	 * Store the toast table's OID in the parent relation's pg_class row
  	 */
  	class_rel = table_open(RelationRelationId, RowExclusiveLock);
  
  	reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relOid));
  	if (!HeapTupleIsValid(reltup))
  		elog(ERROR, "cache lookup failed for relation %u", relOid);
  
  	((Form_pg_class) GETSTRUCT(reltup))->reltoastrelid = toast_relid;
  
  	if (!IsBootstrapProcessingMode())
  	{
  		/* normal case, use a transactional update */
  		CatalogTupleUpdate(class_rel, &reltup->t_self, reltup);
  	}
  	else
  	{
  		/* While bootstrapping, we cannot UPDATE, so overwrite in-place */
  		heap_inplace_update(class_rel, reltup);
  	}
  
  	heap_freetuple(reltup);
  
  	table_close(class_rel, RowExclusiveLock);
  
  	/*
  	 * Register dependency from the toast table to the main, so that the toast
  	 * table will be deleted if the main is.  Skip this in bootstrap mode.
  	 */
  	if (!IsBootstrapProcessingMode())
  	{
  		baseobject.classId = RelationRelationId;
  		baseobject.objectId = relOid;
  		baseobject.objectSubId = 0;
  		toastobject.classId = RelationRelationId;
  		toastobject.objectId = toast_relid;
  		toastobject.objectSubId = 0;
  
  		recordDependencyOn(&toastobject, &baseobject, DEPENDENCY_INTERNAL);
  	}
  
  	/*
  	 * Make changes visible
  	 */
  	CommandCounterIncrement();
  
  	return true;
  }
  
  /*
   * Check to see whether the table needs a TOAST table.
   */
  static bool
  needs_toast_table(Relation rel)
  {
  	/*
  	 * No need to create a TOAST table for partitioned tables.
  	 */
  	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		return false;
  
  	/*
  	 * We cannot allow toasting a shared relation after initdb (because
  	 * there's no way to mark it toasted in other databases' pg_class).
  	 */
  	if (rel->rd_rel->relisshared && !IsBootstrapProcessingMode())
  		return false;
  
  	/*
  	 * Ignore attempts to create toast tables on catalog tables after initdb.
  	 * Which catalogs get toast tables is explicitly chosen in catalog/pg_*.h.
  	 * (We could get here via some ALTER TABLE command if the catalog doesn't
  	 * have a toast table.)
  	 */
  	if (IsCatalogRelation(rel) && !IsBootstrapProcessingMode())
  		return false;
  
  	/* Otherwise, let the AM decide. */
  	return table_relation_needs_toast_table(rel);
  }
  