Introduce access/{table.h, relation.h}, for generic functions from heapam.h.

access/heapam contains functions that are very storage specific (say
heap_insert() and a lot of lower level functions), and fairly generic
infrastructure like relation_open(), heap_open() etc.  In the upcoming
pluggable storage work we're introducing a layer between table
accesses in general and heapam, to allow for different storage
methods. For a bit cleaner separation it thus seems advantageous to
move generic functions like the aforementioned to their own headers.

access/relation.h will contain relation_open() etc, and access/table.h
will contain table_open() (formerly known as heap_open()). I've decided
for table.h not to include relation.h, but we might change that at a
later stage.

relation.h already exists in another directory, but the other
plausible name (rel.h) also conflicts. It'd be nice if there were a
non-conflicting name, but nobody came up with a suggestion. It's
possible that the appropriate way to address the naming conflict would
be to rename nodes/relation.h, which isn't particularly well named.

To avoid breaking a lot of extensions that just use heap_open() etc,
table.h has macros mapping the old names to the new ones, and heapam.h
includes relation, table.h.  That also allows to keep the
bulk renaming of existing callers in a separate commit.

Author: Andres Freund
Discussion: https://postgr.es/m/20190111000539.xbv7s6w7ilcvm7dp@alap3.anarazel.de

src/backend/access/Makefile

@@ -9,6 +9,6 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
-			  tablesample transam
+			  table tablesample transam
 
 include $(top_srcdir)/src/backend/common.mk

src/backend/access/common/Makefile

@@ -13,6 +13,6 @@ top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = bufmask.o heaptuple.o indextuple.o printsimple.o printtup.o \
-	reloptions.o scankey.o session.o tupconvert.o tupdesc.o
+	relation.o reloptions.o scankey.o session.o tupconvert.o tupdesc.o
 
 include $(top_srcdir)/src/backend/common.mk

src/backend/access/common/relation.c

+/*-------------------------------------------------------------------------
+ *
+ * relation.c
+ *	  Generic relation related routines.
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/common/relation.c
+ *
+ * NOTES
+ *	  This file contains relation_ routines that implement access to relations
+ *	  (tables, indexes, etc). Support that's specific to subtypes of relations
+ *	  should go into their respective files, not here.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/relation.h"
+#include "access/xact.h"
+#include "catalog/namespace.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "storage/lmgr.h"
+#include "utils/inval.h"
+#include "utils/syscache.h"
+
+
+/* ----------------
+ *		relation_open - open any relation by relation OID
+ *
+ *		If lockmode is not "NoLock", the specified kind of lock is
+ *		obtained on the relation.  (Generally, NoLock should only be
+ *		used if the caller knows it has some appropriate lock on the
+ *		relation already.)
+ *
+ *		An error is raised if the relation does not exist.
+ *
+ *		NB: a "relation" is anything with a pg_class entry.  The caller is
+ *		expected to check whether the relkind is something it can handle.
+ * ----------------
+ */
+Relation
+relation_open(Oid relationId, LOCKMODE lockmode)
+{
+	Relation	r;
+
+	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
+
+	/* Get the lock before trying to open the relcache entry */
+	if (lockmode != NoLock)
+		LockRelationOid(relationId, lockmode);
+
+	/* The relcache does all the real work... */
+	r = RelationIdGetRelation(relationId);
+
+	if (!RelationIsValid(r))
+		elog(ERROR, "could not open relation with OID %u", relationId);
+
+	/*
+	 * If we didn't get the lock ourselves, assert that caller holds one,
+	 * except in bootstrap mode where no locks are used.
+	 */
+	Assert(lockmode != NoLock ||
+		   IsBootstrapProcessingMode() ||
+		   CheckRelationLockedByMe(r, AccessShareLock, true));
+
+	/* Make note that we've accessed a temporary relation */
+	if (RelationUsesLocalBuffers(r))
+		MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPREL;
+
+	pgstat_initstats(r);
+
+	return r;
+}
+
+/* ----------------
+ *		try_relation_open - open any relation by relation OID
+ *
+ *		Same as relation_open, except return NULL instead of failing
+ *		if the relation does not exist.
+ * ----------------
+ */
+Relation
+try_relation_open(Oid relationId, LOCKMODE lockmode)
+{
+	Relation	r;
+
+	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
+
+	/* Get the lock first */
+	if (lockmode != NoLock)
+		LockRelationOid(relationId, lockmode);
+
+	/*
+	 * Now that we have the lock, probe to see if the relation really exists
+	 * or not.
+	 */
+	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relationId)))
+	{
+		/* Release useless lock */
+		if (lockmode != NoLock)
+			UnlockRelationOid(relationId, lockmode);
+
+		return NULL;
+	}
+
+	/* Should be safe to do a relcache load */
+	r = RelationIdGetRelation(relationId);
+
+	if (!RelationIsValid(r))
+		elog(ERROR, "could not open relation with OID %u", relationId);
+
+	/* If we didn't get the lock ourselves, assert that caller holds one */
+	Assert(lockmode != NoLock ||
+		   CheckRelationLockedByMe(r, AccessShareLock, true));
+
+	/* Make note that we've accessed a temporary relation */
+	if (RelationUsesLocalBuffers(r))
+		MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPREL;
+
+	pgstat_initstats(r);
+
+	return r;
+}
+
+/* ----------------
+ *		relation_openrv - open any relation specified by a RangeVar
+ *
+ *		Same as relation_open, but the relation is specified by a RangeVar.
+ * ----------------
+ */
+Relation
+relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
+{
+	Oid			relOid;
+
+	/*
+	 * Check for shared-cache-inval messages before trying to open the
+	 * relation.  This is needed even if we already hold a lock on the
+	 * relation, because GRANT/REVOKE are executed without taking any lock on
+	 * the target relation, and we want to be sure we see current ACL
+	 * information.  We can skip this if asked for NoLock, on the assumption
+	 * that such a call is not the first one in the current command, and so we
+	 * should be reasonably up-to-date already.  (XXX this all could stand to
+	 * be redesigned, but for the moment we'll keep doing this like it's been
+	 * done historically.)
+	 */
+	if (lockmode != NoLock)
+		AcceptInvalidationMessages();
+
+	/* Look up and lock the appropriate relation using namespace search */
+	relOid = RangeVarGetRelid(relation, lockmode, false);
+
+	/* Let relation_open do the rest */
+	return relation_open(relOid, NoLock);
+}
+
+/* ----------------
+ *		relation_openrv_extended - open any relation specified by a RangeVar
+ *
+ *		Same as relation_openrv, but with an additional missing_ok argument
+ *		allowing a NULL return rather than an error if the relation is not
+ *		found.  (Note that some other causes, such as permissions problems,
+ *		will still result in an ereport.)
+ * ----------------
+ */
+Relation
+relation_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
+						 bool missing_ok)
+{
+	Oid			relOid;
+
+	/*
+	 * Check for shared-cache-inval messages before trying to open the
+	 * relation.  See comments in relation_openrv().
+	 */
+	if (lockmode != NoLock)
+		AcceptInvalidationMessages();
+
+	/* Look up and lock the appropriate relation using namespace search */
+	relOid = RangeVarGetRelid(relation, lockmode, missing_ok);
+
+	/* Return NULL on not-found */
+	if (!OidIsValid(relOid))
+		return NULL;
+
+	/* Let relation_open do the rest */
+	return relation_open(relOid, NoLock);
+}
+
+/* ----------------
+ *		relation_close - close any relation
+ *
+ *		If lockmode is not "NoLock", we then release the specified lock.
+ *
+ *		Note that it is often sensible to hold a lock beyond relation_close;
+ *		in that case, the lock is released automatically at xact end.
+ * ----------------
+ */
+void
+relation_close(Relation relation, LOCKMODE lockmode)
+{
+	LockRelId	relid = relation->rd_lockInfo.lockRelId;
+
+	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
+
+	/* The relcache does the real work... */
+	RelationClose(relation);
+
+	if (lockmode != NoLock)
+		UnlockRelationId(&relid, lockmode);
+}

src/backend/access/heap/heapam.c

@@ -12,12 +12,6 @@
  *
  *
  * INTERFACE ROUTINES
- *		relation_open	- open any relation by relation OID
- *		relation_openrv - open any relation specified by a RangeVar
- *		relation_close	- close any relation
- *		heap_open		- open a heap relation by relation OID
- *		heap_openrv		- open a heap relation specified by a RangeVar
- *		heap_close		- (now just a macro for relation_close)
  *		heap_beginscan	- begin relation scan
  *		heap_rescan		- restart a relation scan
  *		heap_endscan	- end relation scan
@@ -56,7 +50,6 @@
 #include "access/xloginsert.h"
 #include "access/xlogutils.h"
 #include "catalog/catalog.h"
-#include "catalog/namespace.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "port/atomics.h"
@@ -73,7 +66,6 @@
 #include "utils/lsyscache.h"
 #include "utils/relcache.h"
 #include "utils/snapmgr.h"
-#include "utils/syscache.h"
 #include "utils/tqual.h"
 
 
@@ -1103,287 +1095,6 @@ fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
  * ----------------------------------------------------------------
  */
 
-/* ----------------
- *		relation_open - open any relation by relation OID
- *
- *		If lockmode is not "NoLock", the specified kind of lock is
- *		obtained on the relation.  (Generally, NoLock should only be
- *		used if the caller knows it has some appropriate lock on the
- *		relation already.)
- *
- *		An error is raised if the relation does not exist.
- *
- *		NB: a "relation" is anything with a pg_class entry.  The caller is
- *		expected to check whether the relkind is something it can handle.
- * ----------------
- */
-Relation
-relation_open(Oid relationId, LOCKMODE lockmode)
-{
-	Relation	r;
-
-	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
-
-	/* Get the lock before trying to open the relcache entry */
-	if (lockmode != NoLock)
-		LockRelationOid(relationId, lockmode);
-
-	/* The relcache does all the real work... */
-	r = RelationIdGetRelation(relationId);
-
-	if (!RelationIsValid(r))
-		elog(ERROR, "could not open relation with OID %u", relationId);
-
-	/*
-	 * If we didn't get the lock ourselves, assert that caller holds one,
-	 * except in bootstrap mode where no locks are used.
-	 */
-	Assert(lockmode != NoLock ||
-		   IsBootstrapProcessingMode() ||
-		   CheckRelationLockedByMe(r, AccessShareLock, true));
-
-	/* Make note that we've accessed a temporary relation */
-	if (RelationUsesLocalBuffers(r))
-		MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPREL;
-
-	pgstat_initstats(r);
-
-	return r;
-}
-
-/* ----------------
- *		try_relation_open - open any relation by relation OID
- *
- *		Same as relation_open, except return NULL instead of failing
- *		if the relation does not exist.
- * ----------------
- */
-Relation
-try_relation_open(Oid relationId, LOCKMODE lockmode)
-{
-	Relation	r;
-
-	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
-
-	/* Get the lock first */
-	if (lockmode != NoLock)
-		LockRelationOid(relationId, lockmode);
-
-	/*
-	 * Now that we have the lock, probe to see if the relation really exists
-	 * or not.
-	 */
-	if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relationId)))
-	{
-		/* Release useless lock */
-		if (lockmode != NoLock)
-			UnlockRelationOid(relationId, lockmode);
-
-		return NULL;
-	}
-
-	/* Should be safe to do a relcache load */
-	r = RelationIdGetRelation(relationId);
-
-	if (!RelationIsValid(r))
-		elog(ERROR, "could not open relation with OID %u", relationId);
-
-	/* If we didn't get the lock ourselves, assert that caller holds one */
-	Assert(lockmode != NoLock ||
-		   CheckRelationLockedByMe(r, AccessShareLock, true));
-
-	/* Make note that we've accessed a temporary relation */
-	if (RelationUsesLocalBuffers(r))
-		MyXactFlags |= XACT_FLAGS_ACCESSEDTEMPREL;
-
-	pgstat_initstats(r);
-
-	return r;
-}
-
-/* ----------------
- *		relation_openrv - open any relation specified by a RangeVar
- *
- *		Same as relation_open, but the relation is specified by a RangeVar.
- * ----------------
- */
-Relation
-relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
-{
-	Oid			relOid;
-
-	/*
-	 * Check for shared-cache-inval messages before trying to open the
-	 * relation.  This is needed even if we already hold a lock on the
-	 * relation, because GRANT/REVOKE are executed without taking any lock on
-	 * the target relation, and we want to be sure we see current ACL
-	 * information.  We can skip this if asked for NoLock, on the assumption
-	 * that such a call is not the first one in the current command, and so we
-	 * should be reasonably up-to-date already.  (XXX this all could stand to
-	 * be redesigned, but for the moment we'll keep doing this like it's been
-	 * done historically.)
-	 */
-	if (lockmode != NoLock)
-		AcceptInvalidationMessages();
-
-	/* Look up and lock the appropriate relation using namespace search */
-	relOid = RangeVarGetRelid(relation, lockmode, false);
-
-	/* Let relation_open do the rest */
-	return relation_open(relOid, NoLock);
-}
-
-/* ----------------
- *		relation_openrv_extended - open any relation specified by a RangeVar
- *
- *		Same as relation_openrv, but with an additional missing_ok argument
- *		allowing a NULL return rather than an error if the relation is not
- *		found.  (Note that some other causes, such as permissions problems,
- *		will still result in an ereport.)
- * ----------------
- */
-Relation
-relation_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
-						 bool missing_ok)
-{
-	Oid			relOid;
-
-	/*
-	 * Check for shared-cache-inval messages before trying to open the
-	 * relation.  See comments in relation_openrv().
-	 */
-	if (lockmode != NoLock)
-		AcceptInvalidationMessages();
-
-	/* Look up and lock the appropriate relation using namespace search */
-	relOid = RangeVarGetRelid(relation, lockmode, missing_ok);
-
-	/* Return NULL on not-found */
-	if (!OidIsValid(relOid))
-		return NULL;
-
-	/* Let relation_open do the rest */
-	return relation_open(relOid, NoLock);
-}
-
-/* ----------------
- *		relation_close - close any relation
- *
- *		If lockmode is not "NoLock", we then release the specified lock.
- *
- *		Note that it is often sensible to hold a lock beyond relation_close;
- *		in that case, the lock is released automatically at xact end.
- * ----------------
- */
-void
-relation_close(Relation relation, LOCKMODE lockmode)
-{
-	LockRelId	relid = relation->rd_lockInfo.lockRelId;
-
-	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
-
-	/* The relcache does the real work... */
-	RelationClose(relation);
-
-	if (lockmode != NoLock)
-		UnlockRelationId(&relid, lockmode);
-}
-
-
-/* ----------------
- *		heap_open - open a heap relation by relation OID
- *
- *		This is essentially relation_open plus check that the relation
- *		is not an index nor a composite type.  (The caller should also
- *		check that it's not a view or foreign table before assuming it has
- *		storage.)
- * ----------------
- */
-Relation
-heap_open(Oid relationId, LOCKMODE lockmode)
-{
-	Relation	r;
-
-	r = relation_open(relationId, lockmode);
-
-	if (r->rd_rel->relkind == RELKIND_INDEX ||
-		r->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is an index",
-						RelationGetRelationName(r))));
-	else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is a composite type",
-						RelationGetRelationName(r))));
-
-	return r;
-}
-
-/* ----------------
- *		heap_openrv - open a heap relation specified
- *		by a RangeVar node
- *
- *		As above, but relation is specified by a RangeVar.
- * ----------------
- */
-Relation
-heap_openrv(const RangeVar *relation, LOCKMODE lockmode)
-{
-	Relation	r;
-
-	r = relation_openrv(relation, lockmode);
-
-	if (r->rd_rel->relkind == RELKIND_INDEX ||
-		r->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is an index",
-						RelationGetRelationName(r))));
-	else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is a composite type",
-						RelationGetRelationName(r))));
-
-	return r;
-}
-
-/* ----------------
- *		heap_openrv_extended - open a heap relation specified
- *		by a RangeVar node
- *
- *		As above, but optionally return NULL instead of failing for
- *		relation-not-found.
- * ----------------
- */
-Relation
-heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
-					 bool missing_ok)
-{
-	Relation	r;
-
-	r = relation_openrv_extended(relation, lockmode, missing_ok);
-
-	if (r)
-	{
-		if (r->rd_rel->relkind == RELKIND_INDEX ||
-			r->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
-			ereport(ERROR,
-					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-					 errmsg("\"%s\" is an index",
-							RelationGetRelationName(r))));
-		else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
-			ereport(ERROR,
-					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-					 errmsg("\"%s\" is a composite type",
-							RelationGetRelationName(r))));
-	}
-
-	return r;
-}
-
 
 /* ----------------
  *		heap_beginscan	- begin relation scan

src/backend/access/table/Makefile

+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for access/table
+#
+# IDENTIFICATION
+#    src/backend/access/table/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/access/table
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = table.o
+
+include $(top_srcdir)/src/backend/common.mk

src/backend/access/table/table.c

+/*-------------------------------------------------------------------------
+ *
+ * table.c
+ *	  Generic routines for table related code.
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/table/table.c
+ *
+ *
+ * NOTES
+ *	  This file contains table_ routines that implement access to tables (in
+ *	  contrast to other relation types like indexes) that are independent of
+ *	  individual table access methods.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/relation.h"
+#include "access/table.h"
+#include "storage/lmgr.h"
+
+
+/* ----------------
+ *		table_open - open a table relation by relation OID
+ *
+ *		This is essentially relation_open plus check that the relation
+ *		is not an index nor a composite type.  (The caller should also
+ *		check that it's not a view or foreign table before assuming it has
+ *		storage.)
+ * ----------------
+ */
+Relation
+table_open(Oid relationId, LOCKMODE lockmode)
+{
+	Relation	r;
+
+	r = relation_open(relationId, lockmode);
+
+	if (r->rd_rel->relkind == RELKIND_INDEX ||
+		r->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is an index",
+						RelationGetRelationName(r))));
+	else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is a composite type",
+						RelationGetRelationName(r))));
+
+	return r;
+}
+
+/* ----------------
+ *		table_openrv - open a table relation specified
+ *		by a RangeVar node
+ *
+ *		As above, but relation is specified by a RangeVar.
+ * ----------------
+ */
+Relation
+table_openrv(const RangeVar *relation, LOCKMODE lockmode)
+{
+	Relation	r;
+
+	r = relation_openrv(relation, lockmode);
+
+	if (r->rd_rel->relkind == RELKIND_INDEX ||
+		r->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is an index",
+						RelationGetRelationName(r))));
+	else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is a composite type",
+						RelationGetRelationName(r))));
+
+	return r;
+}
+
+/* ----------------
+ *		table_openrv_extended - open a table relation specified
+ *		by a RangeVar node
+ *
+ *		As above, but optionally return NULL instead of failing for
+ *		relation-not-found.
+ * ----------------
+ */
+Relation
+table_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
+					  bool missing_ok)
+{
+	Relation	r;
+
+	r = relation_openrv_extended(relation, lockmode, missing_ok);
+
+	if (r)
+	{
+		if (r->rd_rel->relkind == RELKIND_INDEX ||
+			r->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("\"%s\" is an index",
+							RelationGetRelationName(r))));
+		else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("\"%s\" is a composite type",
+							RelationGetRelationName(r))));
+	}
+
+	return r;
+}
+
+/* ----------------
+ *		table_close - close a table
+ *
+ *		If lockmode is not "NoLock", we then release the specified lock.
+ *
+ *		Note that it is often sensible to hold a lock beyond relation_close;
+ *		in that case, the lock is released automatically at xact end.
+ *		----------------
+ */
+void
+table_close(Relation relation, LOCKMODE lockmode)
+{
+	relation_close(relation, lockmode);
+}

src/include/access/heapam.h

@@ -14,8 +14,10 @@
 #ifndef HEAPAM_H
 #define HEAPAM_H
 
+#include "access/relation.h"	/* for backward compatibility */
 #include "access/sdir.h"
 #include "access/skey.h"
+#include "access/table.h"		/* for backward compatibility */
 #include "nodes/lockoptions.h"
 #include "nodes/primnodes.h"
 #include "storage/bufpage.h"
@@ -67,20 +69,6 @@ typedef struct HeapUpdateFailureData
  * ----------------
  */
 
-/* in heap/heapam.c */
-extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
-extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
-extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
-extern Relation relation_openrv_extended(const RangeVar *relation,
-						 LOCKMODE lockmode, bool missing_ok);
-extern void relation_close(Relation relation, LOCKMODE lockmode);
-
-extern Relation heap_open(Oid relationId, LOCKMODE lockmode);
-extern Relation heap_openrv(const RangeVar *relation, LOCKMODE lockmode);
-extern Relation heap_openrv_extended(const RangeVar *relation,
-					 LOCKMODE lockmode, bool missing_ok);
-
-#define heap_close(r,l)  relation_close(r,l)
 
 /* struct definitions appear in relscan.h */
 typedef struct HeapScanDescData *HeapScanDesc;

src/include/access/relation.h

+/*-------------------------------------------------------------------------
+ *
+ * relation.h
+ *	  Generic relation related routines.
+ *
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/relation.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef ACCESS_RELATION_H
+#define ACCESS_RELATION_H
+
+#include "nodes/primnodes.h"
+#include "utils/relcache.h"
+#include "storage/lockdefs.h"
+
+
+extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
+extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
+extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
+extern Relation relation_openrv_extended(const RangeVar *relation,
+						 LOCKMODE lockmode, bool missing_ok);
+extern void relation_close(Relation relation, LOCKMODE lockmode);
+
+#endif							/* ACCESS_RELATION_H */

src/include/access/table.h

+/*-------------------------------------------------------------------------
+ *
+ * table.h
+ *	  Generic routines for table related code.
+ *
+ *
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/table.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef TABLE_H
+#define TABLE_H
+
+#include "nodes/primnodes.h"
+#include "utils/relcache.h"
+#include "storage/lockdefs.h"
+
+
+extern Relation table_open(Oid relationId, LOCKMODE lockmode);
+extern Relation table_openrv(const RangeVar *relation, LOCKMODE lockmode);
+extern Relation table_openrv_extended(const RangeVar *relation,
+					  LOCKMODE lockmode, bool missing_ok);
+extern void table_close(Relation relation, LOCKMODE lockmode);
+
+/*
+ * heap_ used to be the prefix for these routines, and a lot of code will just
+ * continue to work without adaptions after the introduction of pluggable
+ * storage, therefore just map these names.
+ */
+#define heap_open(r, l)					table_open(r, l)
+#define heap_openrv(r, l)				table_openrv(r, l)
+#define heap_openrv_extended(r, l, m)	table_openrv_extended(r, l, m)
+#define heap_close(r, l)				table_close(r, l)
+
+#endif							/* TABLE_H */