tableam: introduce table AM infrastructure.

This introduces the concept of table access methods, i.e. CREATE
  ACCESS METHOD ... TYPE TABLE and
  CREATE TABLE ... USING (storage-engine).
No table access functionality is delegated to table AMs as of this
commit, that'll be done in following commits.

Subsequent commits will incrementally abstract table access
functionality to be routed through table access methods. That change
is too large to be reviewed & committed at once, so it'll be done
incrementally.

Docs will be updated at the end, as adding them incrementally would
likely make them less coherent, and definitely is a lot more work,
without a lot of benefit.

Table access methods are specified similar to index access methods,
i.e. pg_am.amhandler returns, as INTERNAL, a pointer to a struct with
callbacks. In contrast to index AMs that struct needs to live as long
as a backend, typically that's achieved by just returning a pointer to
a constant struct.

Psql's \d+ now displays a table's access method. That can be disabled
with HIDE_TABLEAM=true, which is mainly useful so regression tests can
be run against different AMs.  It's quite possible that this behaviour
still needs to be fine tuned.

For now it's not allowed to set a table AM for a partitioned table, as
we've not resolved how partitions would inherit that. Disallowing
allows us to introduce, if we decide that's the way forward, such a
behaviour without a compatibility break.

Catversion bumped, to add the heap table AM and references to it.

Author: Haribabu Kommi, Andres Freund, Alvaro Herrera, Dimitri Golgov and others
Discussion:
    https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
    https://postgr.es/m/20160812231527.GA690404@alvherre.pgsql
    https://postgr.es/m/20190107235616.6lur25ph22u5u5av@alap3.anarazel.de
    https://postgr.es/m/20190304234700.w5tmhducs5wxgzls@alap3.anarazel.de

14 files changed, 98 insertions, 7 deletions

diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
new file mode 100644
index 00000000000..caeb5887d5d
--- /dev/null
+++ b/src/include/access/tableam.h
@@ -0,0 +1,48 @@
+/*-------------------------------------------------------------------------
+ *
+ * tableam.h
+ *	  POSTGRES table access method definitions.
+ *
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/tableam.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef TABLEAM_H
+#define TABLEAM_H
+
+#include "utils/guc.h"
+
+
+#define DEFAULT_TABLE_ACCESS_METHOD	"heap"
+
+extern char *default_table_access_method;
+
+
+
+/*
+ * API struct for a table AM.  Note this must be allocated in a
+ * server-lifetime manner, typically as a static const struct, which then gets
+ * returned by FormData_pg_am.amhandler.
+ */
+typedef struct TableAmRoutine
+{
+	/* this must be set to T_TableAmRoutine */
+	NodeTag		type;
+} TableAmRoutine;
+
+
+
+/*
+ * Functions in tableamapi.c
+ */
+extern const TableAmRoutine *GetTableAmRoutine(Oid amhandler);
+extern const TableAmRoutine *GetTableAmRoutineByAmId(Oid amoid);
+extern const TableAmRoutine *GetHeapamTableAmRoutine(void);
+extern bool check_default_table_access_method(char **newval, void **extra,
+								  GucSource source);
+
+#endif							/* TABLEAM_H */
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 0c4c2e11d59..f596ea53511 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201903041
+#define CATALOG_VERSION_NO	201903061
 
 #endif
diff --git a/src/include/catalog/heap.h b/src/include/catalog/heap.h
index 50fb62be9d5..85076d07437 100644
--- a/src/include/catalog/heap.h
+++ b/src/include/catalog/heap.h
@@ -49,6 +49,7 @@ extern Relation heap_create(const char *relname,
 			Oid reltablespace,
 			Oid relid,
 			Oid relfilenode,
+			Oid accessmtd,
 			TupleDesc tupDesc,
 			char relkind,
 			char relpersistence,
@@ -63,6 +64,7 @@ extern Oid heap_create_with_catalog(const char *relname,
 						 Oid reltypeid,
 						 Oid reloftypeid,
 						 Oid ownerid,
+						 Oid accessmtd,
 						 TupleDesc tupdesc,
 						 List *cooked_constraints,
 						 char relkind,
diff --git a/src/include/catalog/pg_am.dat b/src/include/catalog/pg_am.dat
index 08f331d4e10..393b41dd684 100644
--- a/src/include/catalog/pg_am.dat
+++ b/src/include/catalog/pg_am.dat
@@ -12,6 +12,9 @@
 
 [
 
+{ oid => '2', oid_symbol => 'HEAP_TABLE_AM_OID',
+  descr => 'heap table access method',
+  amname => 'heap', amhandler => 'heap_tableam_handler', amtype => 't' },
 { oid => '403', oid_symbol => 'BTREE_AM_OID',
   descr => 'b-tree index access method',
   amname => 'btree', amhandler => 'bthandler', amtype => 'i' },
diff --git a/src/include/catalog/pg_am.h b/src/include/catalog/pg_am.h
index eb3495c36a1..706b5e81cba 100644
--- a/src/include/catalog/pg_am.h
+++ b/src/include/catalog/pg_am.h
@@ -53,6 +53,7 @@ typedef FormData_pg_am *Form_pg_am;
  * Allowed values for amtype
  */
 #define AMTYPE_INDEX					'i' /* index access method */
+#define AMTYPE_TABLE					't' /* table access method */
 
 #endif							/* EXPOSE_TO_CLIENT_CODE */
 
diff --git a/src/include/catalog/pg_class.dat b/src/include/catalog/pg_class.dat
index cccad25c148..ef0cf97ab73 100644
--- a/src/include/catalog/pg_class.dat
+++ b/src/include/catalog/pg_class.dat
@@ -22,7 +22,7 @@
 
 { oid => '1247',
   relname => 'pg_type', relnamespace => 'PGNSP', reltype => '71',
-  reloftype => '0', relowner => 'PGUID', relam => '0', relfilenode => '0',
+  reloftype => '0', relowner => 'PGUID', relam => 'PGHEAPAM', relfilenode => '0',
   reltablespace => '0', relpages => '0', reltuples => '0', relallvisible => '0',
   reltoastrelid => '0', relhasindex => 'f', relisshared => 'f',
   relpersistence => 'p', relkind => 'r', relnatts => '31', relchecks => '0',
@@ -33,7 +33,7 @@
   reloptions => '_null_', relpartbound => '_null_' },
 { oid => '1249',
   relname => 'pg_attribute', relnamespace => 'PGNSP', reltype => '75',
-  reloftype => '0', relowner => 'PGUID', relam => '0', relfilenode => '0',
+  reloftype => '0', relowner => 'PGUID', relam => 'PGHEAPAM', relfilenode => '0',
   reltablespace => '0', relpages => '0', reltuples => '0', relallvisible => '0',
   reltoastrelid => '0', relhasindex => 'f', relisshared => 'f',
   relpersistence => 'p', relkind => 'r', relnatts => '24', relchecks => '0',
@@ -44,7 +44,7 @@
   reloptions => '_null_', relpartbound => '_null_' },
 { oid => '1255',
   relname => 'pg_proc', relnamespace => 'PGNSP', reltype => '81',
-  reloftype => '0', relowner => 'PGUID', relam => '0', relfilenode => '0',
+  reloftype => '0', relowner => 'PGUID', relam => 'PGHEAPAM', relfilenode => '0',
   reltablespace => '0', relpages => '0', reltuples => '0', relallvisible => '0',
   reltoastrelid => '0', relhasindex => 'f', relisshared => 'f',
   relpersistence => 'p', relkind => 'r', relnatts => '29', relchecks => '0',
@@ -55,7 +55,7 @@
   reloptions => '_null_', relpartbound => '_null_' },
 { oid => '1259',
   relname => 'pg_class', relnamespace => 'PGNSP', reltype => '83',
-  reloftype => '0', relowner => 'PGUID', relam => '0', relfilenode => '0',
+  reloftype => '0', relowner => 'PGUID', relam => 'PGHEAPAM', relfilenode => '0',
   reltablespace => '0', relpages => '0', reltuples => '0', relallvisible => '0',
   reltoastrelid => '0', relhasindex => 'f', relisshared => 'f',
   relpersistence => 'p', relkind => 'r', relnatts => '33', relchecks => '0',
diff --git a/src/include/catalog/pg_class.h b/src/include/catalog/pg_class.h
index 5d82ce09a6c..ad698c9e84c 100644
--- a/src/include/catalog/pg_class.h
+++ b/src/include/catalog/pg_class.h
@@ -36,7 +36,7 @@ CATALOG(pg_class,1259,RelationRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(83,Relat
 	Oid			reloftype;		/* OID of entry in pg_type for underlying
 								 * composite type */
 	Oid			relowner;		/* class owner */
-	Oid			relam;			/* index access method; 0 if not an index */
+	Oid			relam;			/* access method; 0 if not a table / index */
 	Oid			relfilenode;	/* identifier of physical storage file */
 
 	/* relfilenode == 0 means it is a "mapped" relation, see relmapper.c */
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 5bb56b2c639..bce909b05ac 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -867,6 +867,12 @@
   proname => 'int4', prorettype => 'int4', proargtypes => 'float4',
   prosrc => 'ftoi4' },
 
+# Table access method handlers
+{ oid => '3', oid_symbol => 'HEAP_TABLE_AM_HANDLER_OID',
+  descr => 'row-oriented heap table access method handler',
+  proname => 'heap_tableam_handler', provolatile => 'v', prorettype => 'table_am_handler',
+  proargtypes => 'internal', prosrc => 'heap_tableam_handler' },
+
 # Index access method handlers
 { oid => '330', descr => 'btree index access method handler',
   proname => 'bthandler', provolatile => 'v', prorettype => 'index_am_handler',
@@ -6981,6 +6987,13 @@
 { oid => '3312', descr => 'I/O',
   proname => 'tsm_handler_out', prorettype => 'cstring',
   proargtypes => 'tsm_handler', prosrc => 'tsm_handler_out' },
+{ oid => '267', descr => 'I/O',
+  proname => 'table_am_handler_in', proisstrict => 'f',
+  prorettype => 'table_am_handler', proargtypes => 'cstring',
+  prosrc => 'table_am_handler_in' },
+{ oid => '268', descr => 'I/O',
+  proname => 'table_am_handler_out', prorettype => 'cstring',
+  proargtypes => 'table_am_handler', prosrc => 'table_am_handler_out' },
 
 # tablesample method handlers
 { oid => '3313', descr => 'BERNOULLI tablesample method handler',
diff --git a/src/include/catalog/pg_type.dat b/src/include/catalog/pg_type.dat
index 4b7750d4398..4497ff6a2c5 100644
--- a/src/include/catalog/pg_type.dat
+++ b/src/include/catalog/pg_type.dat
@@ -580,6 +580,11 @@
   typcategory => 'P', typinput => 'tsm_handler_in',
   typoutput => 'tsm_handler_out', typreceive => '-', typsend => '-',
   typalign => 'i' },
+{ oid => '269',
+  typname => 'table_am_handler', typlen => '4', typbyval => 't', typtype => 'p',
+  typcategory => 'P', typinput => 'table_am_handler_in',
+  typoutput => 'table_am_handler_out', typreceive => '-', typsend => '-',
+  typalign => 'i' },
 { oid => '3831',
   descr => 'pseudo-type representing a polymorphic base type that is a range',
   typname => 'anyrange', typlen => '-1', typbyval => 'f', typtype => 'p',
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index f9389257c60..ffb4cd4bcc4 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -504,6 +504,7 @@ typedef enum NodeTag
 	T_InlineCodeBlock,			/* in nodes/parsenodes.h */
 	T_FdwRoutine,				/* in foreign/fdwapi.h */
 	T_IndexAmRoutine,			/* in access/amapi.h */
+	T_TableAmRoutine,			/* in access/tableam.h */
 	T_TsmRoutine,				/* in access/tsmapi.h */
 	T_ForeignKeyCacheInfo,		/* in utils/rel.h */
 	T_CallContext,				/* in nodes/parsenodes.h */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index a7e859dc90e..fe35783359e 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2044,6 +2044,7 @@ typedef struct CreateStmt
 	List	   *options;		/* options from WITH clause */
 	OnCommitAction oncommit;	/* what do we do at COMMIT? */
 	char	   *tablespacename; /* table space to use, or NULL */
+	char	   *accessMethod;	/* table access method */
 	bool		if_not_exists;	/* just do nothing if it already exists? */
 } CreateStmt;
 
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index a7efae70381..f9b1cf2df72 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -111,6 +111,7 @@ typedef struct IntoClause
 
 	RangeVar   *rel;			/* target relation name */
 	List	   *colNames;		/* column names to assign, or NIL */
+	char	   *accessMethod;	/* table access method */
 	List	   *options;		/* options from WITH clause */
 	OnCommitAction onCommit;	/* what do we do at COMMIT? */
 	char	   *tableSpaceName; /* table space to use, or NULL */
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 1d054653039..9d805ca23d2 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -124,6 +124,20 @@ typedef struct RelationData
 	 */
 	bytea	   *rd_options;		/* parsed pg_class.reloptions */
 
+	/*
+	 * Oid of the handler for this relation. For an index this is a function
+	 * returning IndexAmRoutine, for table like relations a function returning
+	 * TableAmRoutine.  This is stored separately from rd_indam, rd_tableam as
+	 * its lookup requires syscache access, but during relcache bootstrap we
+	 * need to be able to initialize rd_tableam without syscache lookups.
+	 */
+	Oid			rd_amhandler;	/* OID of index AM's handler function */
+
+	/*
+	 * Table access method.
+	 */
+	const struct TableAmRoutine *rd_tableam;
+
 	/* These are non-NULL only for an index relation: */
 	Form_pg_index rd_index;		/* pg_index tuple describing this index */
 	/* use "struct" here to avoid needing to include htup.h: */
@@ -144,7 +158,6 @@ typedef struct RelationData
 	 * rd_indexcxt.  A relcache reset will include freeing that chunk and
 	 * setting rd_amcache = NULL.
 	 */
-	Oid			rd_amhandler;	/* OID of index AM's handler function */
 	MemoryContext rd_indexcxt;	/* private memory cxt for this stuff */
 	/* use "struct" here to avoid needing to include amapi.h: */
 	struct IndexAmRoutine *rd_indam;	/* index AM's API struct */
diff --git a/src/include/utils/relcache.h b/src/include/utils/relcache.h
index a80e335374d..8f5bd676498 100644
--- a/src/include/utils/relcache.h
+++ b/src/include/utils/relcache.h
@@ -75,6 +75,8 @@ extern void RelationInitIndexAccessInfo(Relation relation);
 struct PublicationActions;
 extern struct PublicationActions *GetRelationPublicationActions(Relation relation);
 
+extern void RelationInitTableAccessMethod(Relation relation);
+
 /*
  * Routines to support ereport() reports of relation-related errors
  */
@@ -97,6 +99,7 @@ extern Relation RelationBuildLocalRelation(const char *relname,
 						   Oid relnamespace,
 						   TupleDesc tupDesc,
 						   Oid relid,
+						   Oid accessmtd,
 						   Oid relfilenode,
 						   Oid reltablespace,
 						   bool shared_relation,