Rename pg_sequence_read_tuple() to pg_get_sequence_data()

This commit removes log_cnt from the tuple returned by the SQL function.
This field is an internal counter that tracks when a WAL record should
be generated for a sequence, and it is reset each time the sequence is
restored or recovered.  It is not necessary to rebuild the sequence DDL
commands for pg_dump and pg_upgrade where this function is used.  The
field can still be queried with a scan of the "table" created
under-the-hood for a sequence.

Issue noticed while hacking on a feature that can rely on this new
function rather than pg_sequence_last_value(), aimed at making sequence
computation more easily pluggable.

Bump catalog version.

Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/Zsvka3r-y2ZoXAdH@paquier.xyz

Author: michaelpq

src/backend/commands/sequence.c

@@ -1781,23 +1781,22 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
  * without needing to individually query each sequence relation.
  */
 Datum
-pg_sequence_read_tuple(PG_FUNCTION_ARGS)
+pg_get_sequence_data(PG_FUNCTION_ARGS)
 {
+#define PG_GET_SEQUENCE_DATA_COLS	2
 	Oid			relid = PG_GETARG_OID(0);
 	SeqTable	elm;
 	Relation	seqrel;
-	Datum		values[SEQ_COL_LASTCOL] = {0};
-	bool		isnull[SEQ_COL_LASTCOL] = {0};
+	Datum		values[PG_GET_SEQUENCE_DATA_COLS] = {0};
+	bool		isnull[PG_GET_SEQUENCE_DATA_COLS] = {0};
 	TupleDesc	resultTupleDesc;
 	HeapTuple	resultHeapTuple;
 	Datum		result;
 
-	resultTupleDesc = CreateTemplateTupleDesc(SEQ_COL_LASTCOL);
+	resultTupleDesc = CreateTemplateTupleDesc(PG_GET_SEQUENCE_DATA_COLS);
 	TupleDescInitEntry(resultTupleDesc, (AttrNumber) 1, "last_value",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(resultTupleDesc, (AttrNumber) 2, "log_cnt",
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(resultTupleDesc, (AttrNumber) 3, "is_called",
+	TupleDescInitEntry(resultTupleDesc, (AttrNumber) 2, "is_called",
 					   BOOLOID, -1, 0);
 	resultTupleDesc = BlessTupleDesc(resultTupleDesc);
 
@@ -1818,8 +1817,7 @@ pg_sequence_read_tuple(PG_FUNCTION_ARGS)
 		seq = read_seq_tuple(seqrel, &buf, &seqtuple);
 
 		values[0] = Int64GetDatum(seq->last_value);
-		values[1] = Int64GetDatum(seq->log_cnt);
-		values[2] = BoolGetDatum(seq->is_called);
+		values[1] = BoolGetDatum(seq->is_called);
 
 		UnlockReleaseBuffer(buf);
 	}
@@ -1831,6 +1829,7 @@ pg_sequence_read_tuple(PG_FUNCTION_ARGS)
 	resultHeapTuple = heap_form_tuple(resultTupleDesc, values, isnull);
 	result = HeapTupleGetDatum(resultHeapTuple);
 	PG_RETURN_DATUM(result);
+#undef PG_GET_SEQUENCE_DATA_COLS
 }
 
 

src/bin/pg_dump/pg_dump.c

@@ -17381,7 +17381,7 @@ collectSequences(Archive *fout)
 	 * versions, but for now it seems unlikely to be worth it.
 	 *
 	 * Since version 18, we can gather the sequence data in this query with
-	 * pg_sequence_read_tuple(), but we only do so for non-schema-only dumps.
+	 * pg_get_sequence_data(), but we only do so for non-schema-only dumps.
 	 */
 	if (fout->remoteVersion < 100000)
 		return;
@@ -17401,7 +17401,7 @@ collectSequences(Archive *fout)
 			"seqcache, seqcycle, "
 			"last_value, is_called "
 			"FROM pg_catalog.pg_sequence, "
-			"pg_sequence_read_tuple(seqrelid) "
+			"pg_get_sequence_data(seqrelid) "
 			"ORDER BY seqrelid;";
 
 	res = ExecuteSqlQuery(fout, query, PGRES_TUPLES_OK);

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202408122
+#define CATALOG_VERSION_NO	202408301
 
 #endif

src/include/catalog/pg_proc.dat

@@ -3330,11 +3330,11 @@
   prorettype => 'int8', proargtypes => 'regclass',
   prosrc => 'pg_sequence_last_value' },
 { oid => '9876', descr => 'return sequence tuple, for use by pg_dump',
-  proname => 'pg_sequence_read_tuple', provolatile => 'v', proparallel => 'u',
+  proname => 'pg_get_sequence_data', provolatile => 'v', proparallel => 'u',
   prorettype => 'record', proargtypes => 'regclass',
-  proallargtypes => '{regclass,int8,int8,bool}', proargmodes => '{i,o,o,o}',
-  proargnames => '{sequence_oid,last_value,log_cnt,is_called}',
-  prosrc => 'pg_sequence_read_tuple' },
+  proallargtypes => '{regclass,int8,bool}', proargmodes => '{i,o,o}',
+  proargnames => '{sequence_oid,last_value,is_called}',
+  prosrc => 'pg_get_sequence_data' },
 
 { oid => '275', descr => 'return the next oid for a system table',
   proname => 'pg_nextoid', provolatile => 'v', proparallel => 'u',

src/test/regress/expected/sequence.out

@@ -839,11 +839,11 @@ SELECT nextval('test_seq1');
        3
 (1 row)
 
--- pg_sequence_read_tuple
-SELECT * FROM pg_sequence_read_tuple('test_seq1');
- last_value | log_cnt | is_called 
-------------+---------+-----------
-         10 |      32 | t
+-- pg_get_sequence_data
+SELECT * FROM pg_get_sequence_data('test_seq1');
+ last_value | is_called 
+------------+-----------
+         10 | t
 (1 row)
 
 DROP SEQUENCE test_seq1;

src/test/regress/sql/sequence.sql

@@ -413,7 +413,7 @@ SELECT nextval('test_seq1');
 SELECT nextval('test_seq1');
 SELECT nextval('test_seq1');
 
--- pg_sequence_read_tuple
-SELECT * FROM pg_sequence_read_tuple('test_seq1');
+-- pg_get_sequence_data
+SELECT * FROM pg_get_sequence_data('test_seq1');
 
 DROP SEQUENCE test_seq1;