Remove catalog function currtid()

currtid() and currtid2() are an undocumented set of functions whose sole
known user is the Postgres ODBC driver, able to retrieve the latest TID
version for a tuple given by the caller of those functions.

As used by Postgres ODBC, currtid() is a shortcut able to retrieve the
last TID loaded into a backend by passing an OID of 0 (magic value)
after a tuple insertion.  This is removed in this commit, as it became
obsolete after the driver began using "RETURNING ctid" with inserts, a
clause supported since Postgres 8.2 (using RETURNING is better for
performance anyway as it reduces the number of round-trips to the
backend).

currtid2() is still used by the driver, so this remains around for now.
Note that this function is kept in its original shape for backward
compatibility reasons.

Per discussion with many people, including Andres Freund, Peter
Eisentraut, Álvaro Herrera, Hiroshi Inoue, Tom Lane and myself.

Bump catalog version.

Discussion: https://postgr.es/m/20200603021448.GB89559@paquier.xyz

src/backend/executor/nodeModifyTable.c

@@ -645,10 +645,7 @@ ExecInsert(ModifyTableState *mtstate,
 	}
 
 	if (canSetTag)
-	{
 		(estate->es_processed)++;
-		setLastTid(&slot->tts_tid);
-	}
 
 	/*
 	 * If this insert is the result of a partition key update that moved the

src/backend/utils/adt/tid.c

@@ -47,6 +47,8 @@
 #define DELIM			','
 #define NTIDARGS		2
 
+static ItemPointer currtid_for_view(Relation viewrel, ItemPointer tid);
+
 /* ----------------------------------------------------------------
  *		tidin
  * ----------------------------------------------------------------
@@ -275,12 +277,44 @@ hashtidextended(PG_FUNCTION_ARGS)
  *	Maybe these implementations should be moved to another place
  */
 
-static ItemPointerData Current_last_tid = {{0, 0}, 0};
-
-void
-setLastTid(const ItemPointer tid)
+/*
+ * Utility wrapper for current CTID functions.
+ *		Returns the latest version of a tuple pointing at "tid" for
+ *		relation "rel".
+ */
+static ItemPointer
+currtid_internal(Relation rel, ItemPointer tid)
 {
-	Current_last_tid = *tid;
+	ItemPointer result;
+	AclResult	aclresult;
+	Snapshot	snapshot;
+	TableScanDesc scan;
+
+	result = (ItemPointer) palloc(sizeof(ItemPointerData));
+
+	aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
+								  ACL_SELECT);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
+					   RelationGetRelationName(rel));
+
+	if (rel->rd_rel->relkind == RELKIND_VIEW)
+		return currtid_for_view(rel, tid);
+
+	if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
+		elog(ERROR, "cannot look at latest visible tid for relation \"%s.%s\"",
+			 get_namespace_name(RelationGetNamespace(rel)),
+			 RelationGetRelationName(rel));
+
+	ItemPointerCopy(tid, result);
+
+	snapshot = RegisterSnapshot(GetLatestSnapshot());
+	scan = table_beginscan_tid(rel, snapshot);
+	table_tuple_get_latest_tid(scan, result);
+	table_endscan(scan);
+	UnregisterSnapshot(snapshot);
+
+	return result;
 }
 
 /*
@@ -288,7 +322,7 @@ setLastTid(const ItemPointer tid)
  *		CTID should be defined in the view and it must
  *		correspond to the CTID of a base relation.
  */
-static Datum
+static ItemPointer
 currtid_for_view(Relation viewrel, ItemPointer tid)
 {
 	TupleDesc	att = RelationGetDescr(viewrel);
@@ -338,12 +372,12 @@ currtid_for_view(Relation viewrel, ItemPointer tid)
 					rte = rt_fetch(var->varno, query->rtable);
 					if (rte)
 					{
-						Datum		result;
+						ItemPointer result;
+						Relation	rel;
 
-						result = DirectFunctionCall2(currtid_byreloid,
-													 ObjectIdGetDatum(rte->relid),
-													 PointerGetDatum(tid));
-						table_close(viewrel, AccessShareLock);
+						rel = table_open(rte->relid, AccessShareLock);
+						result = currtid_internal(rel, tid);
+						table_close(rel, AccessShareLock);
 						return result;
 					}
 				}
@@ -352,56 +386,14 @@ currtid_for_view(Relation viewrel, ItemPointer tid)
 		}
 	}
 	elog(ERROR, "currtid cannot handle this view");
-	return (Datum) 0;
-}
-
-Datum
-currtid_byreloid(PG_FUNCTION_ARGS)
-{
-	Oid			reloid = PG_GETARG_OID(0);
-	ItemPointer tid = PG_GETARG_ITEMPOINTER(1);
-	ItemPointer result;
-	Relation	rel;
-	AclResult	aclresult;
-	Snapshot	snapshot;
-	TableScanDesc scan;
-
-	result = (ItemPointer) palloc(sizeof(ItemPointerData));
-	if (!reloid)
-	{
-		*result = Current_last_tid;
-		PG_RETURN_ITEMPOINTER(result);
-	}
-
-	rel = table_open(reloid, AccessShareLock);
-
-	aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
-								  ACL_SELECT);
-	if (aclresult != ACLCHECK_OK)
-		aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
-					   RelationGetRelationName(rel));
-
-	if (rel->rd_rel->relkind == RELKIND_VIEW)
-		return currtid_for_view(rel, tid);
-
-	if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
-		elog(ERROR, "cannot look at latest visible tid for relation \"%s.%s\"",
-			 get_namespace_name(RelationGetNamespace(rel)),
-			 RelationGetRelationName(rel));
-
-	ItemPointerCopy(tid, result);
-
-	snapshot = RegisterSnapshot(GetLatestSnapshot());
-	scan = table_beginscan_tid(rel, snapshot);
-	table_tuple_get_latest_tid(scan, result);
-	table_endscan(scan);
-	UnregisterSnapshot(snapshot);
-
-	table_close(rel, AccessShareLock);
-
-	PG_RETURN_ITEMPOINTER(result);
+	return NULL;
 }
 
+/*
+ * currtid_byrelname
+ *		Get the latest tuple version of the tuple pointing at a CTID, for a
+ *		given relation name.
+ */
 Datum
 currtid_byrelname(PG_FUNCTION_ARGS)
 {
@@ -410,35 +402,12 @@ currtid_byrelname(PG_FUNCTION_ARGS)
 	ItemPointer result;
 	RangeVar   *relrv;
 	Relation	rel;
-	AclResult	aclresult;
-	Snapshot	snapshot;
-	TableScanDesc scan;
 
 	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
 	rel = table_openrv(relrv, AccessShareLock);
 
-	aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
-								  ACL_SELECT);
-	if (aclresult != ACLCHECK_OK)
-		aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
-					   RelationGetRelationName(rel));
-
-	if (rel->rd_rel->relkind == RELKIND_VIEW)
-		return currtid_for_view(rel, tid);
-
-	if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
-		elog(ERROR, "cannot look at latest visible tid for relation \"%s.%s\"",
-			 get_namespace_name(RelationGetNamespace(rel)),
-			 RelationGetRelationName(rel));
-
-	result = (ItemPointer) palloc(sizeof(ItemPointerData));
-	ItemPointerCopy(tid, result);
-
-	snapshot = RegisterSnapshot(GetLatestSnapshot());
-	scan = table_beginscan_tid(rel, snapshot);
-	table_tuple_get_latest_tid(scan, result);
-	table_endscan(scan);
-	UnregisterSnapshot(snapshot);
+	/* grab the latest tuple version associated to this CTID */
+	result = currtid_internal(rel, tid);
 
 	table_close(rel, AccessShareLock);
 

src/include/access/heapam.h

@@ -129,7 +129,6 @@ extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation,
 								   bool *all_dead, bool first_call);
 
 extern void heap_get_latest_tid(TableScanDesc scan, ItemPointer tid);
-extern void setLastTid(const ItemPointer tid);
 
 extern BulkInsertState GetBulkInsertState(void);
 extern void FreeBulkInsertState(BulkInsertState);

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202011241
+#define CATALOG_VERSION_NO	202011251
 
 #endif

src/include/catalog/pg_proc.dat

@@ -2549,9 +2549,6 @@
 { oid => '1292',
   proname => 'tideq', proleakproof => 't', prorettype => 'bool',
   proargtypes => 'tid tid', prosrc => 'tideq' },
-{ oid => '1293', descr => 'latest tid of a tuple',
-  proname => 'currtid', provolatile => 'v', proparallel => 'u',
-  prorettype => 'tid', proargtypes => 'oid tid', prosrc => 'currtid_byreloid' },
 { oid => '1294', descr => 'latest tid of a tuple',
   proname => 'currtid2', provolatile => 'v', proparallel => 'u',
   prorettype => 'tid', proargtypes => 'text tid',

src/test/regress/expected/tid.out

@@ -15,21 +15,13 @@ SELECT max(ctid) FROM tid_tab;
 (1 row)
 
 TRUNCATE tid_tab;
--- Tests for currtid() and currtid2() with various relation kinds
+-- Tests for currtid2() with various relation kinds
 -- Materialized view
 CREATE MATERIALIZED VIEW tid_matview AS SELECT a FROM tid_tab;
-SELECT currtid('tid_matview'::regclass::oid, '(0,1)'::tid); -- fails
-ERROR:  tid (0, 1) is not valid for relation "tid_matview"
 SELECT currtid2('tid_matview'::text, '(0,1)'::tid); -- fails
 ERROR:  tid (0, 1) is not valid for relation "tid_matview"
 INSERT INTO tid_tab VALUES (1);
 REFRESH MATERIALIZED VIEW tid_matview;
-SELECT currtid('tid_matview'::regclass::oid, '(0,1)'::tid); -- ok
- currtid 
----------
- (0,1)
-(1 row)
-
 SELECT currtid2('tid_matview'::text, '(0,1)'::tid); -- ok
  currtid2 
 ----------
@@ -40,12 +32,6 @@ DROP MATERIALIZED VIEW tid_matview;
 TRUNCATE tid_tab;
 -- Sequence
 CREATE SEQUENCE tid_seq;
-SELECT currtid('tid_seq'::regclass::oid, '(0,1)'::tid); -- ok
- currtid 
----------
- (0,1)
-(1 row)
-
 SELECT currtid2('tid_seq'::text, '(0,1)'::tid); -- ok
  currtid2 
 ----------
@@ -55,39 +41,25 @@ SELECT currtid2('tid_seq'::text, '(0,1)'::tid); -- ok
 DROP SEQUENCE tid_seq;
 -- Index, fails with incorrect relation type
 CREATE INDEX tid_ind ON tid_tab(a);
-SELECT currtid('tid_ind'::regclass::oid, '(0,1)'::tid); -- fails
-ERROR:  "tid_ind" is an index
 SELECT currtid2('tid_ind'::text, '(0,1)'::tid); -- fails
 ERROR:  "tid_ind" is an index
 DROP INDEX tid_ind;
 -- Partitioned table, no storage
 CREATE TABLE tid_part (a int) PARTITION BY RANGE (a);
-SELECT currtid('tid_part'::regclass::oid, '(0,1)'::tid); -- fails
-ERROR:  cannot look at latest visible tid for relation "public.tid_part"
 SELECT currtid2('tid_part'::text, '(0,1)'::tid); -- fails
 ERROR:  cannot look at latest visible tid for relation "public.tid_part"
 DROP TABLE tid_part;
 -- Views
 -- ctid not defined in the view
 CREATE VIEW tid_view_no_ctid AS SELECT a FROM tid_tab;
-SELECT currtid('tid_view_no_ctid'::regclass::oid, '(0,1)'::tid); -- fails
-ERROR:  currtid cannot handle views with no CTID
 SELECT currtid2('tid_view_no_ctid'::text, '(0,1)'::tid); -- fails
 ERROR:  currtid cannot handle views with no CTID
 DROP VIEW tid_view_no_ctid;
 -- ctid fetched directly from the source table.
 CREATE VIEW tid_view_with_ctid AS SELECT ctid, a FROM tid_tab;
-SELECT currtid('tid_view_with_ctid'::regclass::oid, '(0,1)'::tid); -- fails
-ERROR:  tid (0, 1) is not valid for relation "tid_tab"
 SELECT currtid2('tid_view_with_ctid'::text, '(0,1)'::tid); -- fails
 ERROR:  tid (0, 1) is not valid for relation "tid_tab"
 INSERT INTO tid_tab VALUES (1);
-SELECT currtid('tid_view_with_ctid'::regclass::oid, '(0,1)'::tid); -- ok
- currtid 
----------
- (0,1)
-(1 row)
-
 SELECT currtid2('tid_view_with_ctid'::text, '(0,1)'::tid); -- ok
  currtid2 
 ----------
@@ -98,8 +70,6 @@ DROP VIEW tid_view_with_ctid;
 TRUNCATE tid_tab;
 -- ctid attribute with incorrect data type
 CREATE VIEW tid_view_fake_ctid AS SELECT 1 AS ctid, 2 AS a;
-SELECT currtid('tid_view_fake_ctid'::regclass::oid, '(0,1)'::tid); -- fails
-ERROR:  ctid isn't of type TID
 SELECT currtid2('tid_view_fake_ctid'::text, '(0,1)'::tid); -- fails
 ERROR:  ctid isn't of type TID
 DROP VIEW tid_view_fake_ctid;

src/test/regress/sql/tid.sql

@@ -8,55 +8,46 @@ SELECT min(ctid) FROM tid_tab;
 SELECT max(ctid) FROM tid_tab;
 TRUNCATE tid_tab;
 
--- Tests for currtid() and currtid2() with various relation kinds
+-- Tests for currtid2() with various relation kinds
 
 -- Materialized view
 CREATE MATERIALIZED VIEW tid_matview AS SELECT a FROM tid_tab;
-SELECT currtid('tid_matview'::regclass::oid, '(0,1)'::tid); -- fails
 SELECT currtid2('tid_matview'::text, '(0,1)'::tid); -- fails
 INSERT INTO tid_tab VALUES (1);
 REFRESH MATERIALIZED VIEW tid_matview;
-SELECT currtid('tid_matview'::regclass::oid, '(0,1)'::tid); -- ok
 SELECT currtid2('tid_matview'::text, '(0,1)'::tid); -- ok
 DROP MATERIALIZED VIEW tid_matview;
 TRUNCATE tid_tab;
 
 -- Sequence
 CREATE SEQUENCE tid_seq;
-SELECT currtid('tid_seq'::regclass::oid, '(0,1)'::tid); -- ok
 SELECT currtid2('tid_seq'::text, '(0,1)'::tid); -- ok
 DROP SEQUENCE tid_seq;
 
 -- Index, fails with incorrect relation type
 CREATE INDEX tid_ind ON tid_tab(a);
-SELECT currtid('tid_ind'::regclass::oid, '(0,1)'::tid); -- fails
 SELECT currtid2('tid_ind'::text, '(0,1)'::tid); -- fails
 DROP INDEX tid_ind;
 
 -- Partitioned table, no storage
 CREATE TABLE tid_part (a int) PARTITION BY RANGE (a);
-SELECT currtid('tid_part'::regclass::oid, '(0,1)'::tid); -- fails
 SELECT currtid2('tid_part'::text, '(0,1)'::tid); -- fails
 DROP TABLE tid_part;
 
 -- Views
 -- ctid not defined in the view
 CREATE VIEW tid_view_no_ctid AS SELECT a FROM tid_tab;
-SELECT currtid('tid_view_no_ctid'::regclass::oid, '(0,1)'::tid); -- fails
 SELECT currtid2('tid_view_no_ctid'::text, '(0,1)'::tid); -- fails
 DROP VIEW tid_view_no_ctid;
 -- ctid fetched directly from the source table.
 CREATE VIEW tid_view_with_ctid AS SELECT ctid, a FROM tid_tab;
-SELECT currtid('tid_view_with_ctid'::regclass::oid, '(0,1)'::tid); -- fails
 SELECT currtid2('tid_view_with_ctid'::text, '(0,1)'::tid); -- fails
 INSERT INTO tid_tab VALUES (1);
-SELECT currtid('tid_view_with_ctid'::regclass::oid, '(0,1)'::tid); -- ok
 SELECT currtid2('tid_view_with_ctid'::text, '(0,1)'::tid); -- ok
 DROP VIEW tid_view_with_ctid;
 TRUNCATE tid_tab;
 -- ctid attribute with incorrect data type
 CREATE VIEW tid_view_fake_ctid AS SELECT 1 AS ctid, 2 AS a;
-SELECT currtid('tid_view_fake_ctid'::regclass::oid, '(0,1)'::tid); -- fails
 SELECT currtid2('tid_view_fake_ctid'::text, '(0,1)'::tid); -- fails
 DROP VIEW tid_view_fake_ctid;