Move WAL sequence code into its own file

This split exists for most of the other RMGRs, and makes cleaner the
separation between the WAL code, the redo code and the record
description code (already in its own file) when it comes to the sequence
RMGR.  The redo and masking routines are moved to a new file,
sequence_xlog.c.  All the RMGR routines are now located in a new header,
sequence_xlog.h.

This separation is useful for a different patch related to sequences
that I have been working on, where it makes a refactoring of sequence.c
easier if its RMGR routines and its core routines are split.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/aSfTxIWjiXkTKh1E@paquier.xyz

src/backend/access/rmgrdesc/seqdesc.c

@@ -14,7 +14,7 @@
  */
 #include "postgres.h"
 
-#include "commands/sequence.h"
+#include "commands/sequence_xlog.h"
 
 
 void

src/backend/access/transam/rmgr.c

@@ -33,7 +33,7 @@
 #include "access/xact.h"
 #include "catalog/storage_xlog.h"
 #include "commands/dbcommands_xlog.h"
-#include "commands/sequence.h"
+#include "commands/sequence_xlog.h"
 #include "commands/tablespace.h"
 #include "replication/decode.h"
 #include "replication/message.h"

src/backend/commands/Makefile

@@ -53,6 +53,7 @@ OBJS = \
 	schemacmds.o \
 	seclabel.o \
 	sequence.o \
+	sequence_xlog.o \
 	statscmds.o \
 	subscriptioncmds.o \
 	tablecmds.o \

src/backend/commands/meson.build

@@ -41,6 +41,7 @@ backend_sources += files(
   'schemacmds.c',
   'seclabel.c',
   'sequence.c',
+  'sequence_xlog.c',
   'statscmds.c',
   'subscriptioncmds.c',
   'tablecmds.c',

src/backend/commands/sequence.c

@@ -14,7 +14,6 @@
  */
 #include "postgres.h"
 
-#include "access/bufmask.h"
 #include "access/htup_details.h"
 #include "access/multixact.h"
 #include "access/relation.h"
@@ -22,9 +21,7 @@
 #include "access/table.h"
 #include "access/transam.h"
 #include "access/xact.h"
-#include "access/xlog.h"
 #include "access/xloginsert.h"
-#include "access/xlogutils.h"
 #include "catalog/dependency.h"
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
@@ -34,11 +31,13 @@
 #include "catalog/storage_xlog.h"
 #include "commands/defrem.h"
 #include "commands/sequence.h"
+#include "commands/sequence_xlog.h"
 #include "commands/tablecmds.h"
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "parser/parse_type.h"
+#include "storage/bufmgr.h"
 #include "storage/lmgr.h"
 #include "storage/proc.h"
 #include "storage/smgr.h"
@@ -58,16 +57,6 @@
  */
 #define SEQ_LOG_VALS	32
 
-/*
- * The "special area" of a sequence's buffer page looks like this.
- */
-#define SEQ_MAGIC	  0x1717
-
-typedef struct sequence_magic
-{
-	uint32		magic;
-} sequence_magic;
-
 /*
  * We store a SeqTable item for every sequence we have touched in the current
  * session.  This is needed to hold onto nextval/currval state.  (We can't
@@ -1907,56 +1896,6 @@ pg_sequence_last_value(PG_FUNCTION_ARGS)
 		PG_RETURN_NULL();
 }
 
-
-void
-seq_redo(XLogReaderState *record)
-{
-	XLogRecPtr	lsn = record->EndRecPtr;
-	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
-	Buffer		buffer;
-	Page		page;
-	Page		localpage;
-	char	   *item;
-	Size		itemsz;
-	xl_seq_rec *xlrec = (xl_seq_rec *) XLogRecGetData(record);
-	sequence_magic *sm;
-
-	if (info != XLOG_SEQ_LOG)
-		elog(PANIC, "seq_redo: unknown op code %u", info);
-
-	buffer = XLogInitBufferForRedo(record, 0);
-	page = BufferGetPage(buffer);
-
-	/*
-	 * We always reinit the page.  However, since this WAL record type is also
-	 * used for updating sequences, it's possible that a hot-standby backend
-	 * is examining the page concurrently; so we mustn't transiently trash the
-	 * buffer.  The solution is to build the correct new page contents in
-	 * local workspace and then memcpy into the buffer.  Then only bytes that
-	 * are supposed to change will change, even transiently. We must palloc
-	 * the local page for alignment reasons.
-	 */
-	localpage = (Page) palloc(BufferGetPageSize(buffer));
-
-	PageInit(localpage, BufferGetPageSize(buffer), sizeof(sequence_magic));
-	sm = (sequence_magic *) PageGetSpecialPointer(localpage);
-	sm->magic = SEQ_MAGIC;
-
-	item = (char *) xlrec + sizeof(xl_seq_rec);
-	itemsz = XLogRecGetDataLen(record) - sizeof(xl_seq_rec);
-
-	if (PageAddItem(localpage, item, itemsz, FirstOffsetNumber, false, false) == InvalidOffsetNumber)
-		elog(PANIC, "seq_redo: failed to add item to page");
-
-	PageSetLSN(localpage, lsn);
-
-	memcpy(page, localpage, BufferGetPageSize(buffer));
-	MarkBufferDirty(buffer);
-	UnlockReleaseBuffer(buffer);
-
-	pfree(localpage);
-}
-
 /*
  * Flush cached sequence information.
  */
@@ -1971,14 +1910,3 @@ ResetSequenceCaches(void)
 
 	last_used_seq = NULL;
 }
-
-/*
- * Mask a Sequence page before performing consistency checks on it.
- */
-void
-seq_mask(char *page, BlockNumber blkno)
-{
-	mask_page_lsn_and_checksum(page);
-
-	mask_unused_space(page);
-}

src/backend/commands/sequence_xlog.c

@@ -0,0 +1,80 @@
+/*-------------------------------------------------------------------------
+ *
+ * sequence.c
+ *	  RMGR WAL routines for sequences.
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/sequence_xlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/bufmask.h"
+#include "access/xlogutils.h"
+#include "commands/sequence_xlog.h"
+#include "storage/bufmgr.h"
+
+void
+seq_redo(XLogReaderState *record)
+{
+	XLogRecPtr	lsn = record->EndRecPtr;
+	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+	Buffer		buffer;
+	Page		page;
+	Page		localpage;
+	char	   *item;
+	Size		itemsz;
+	xl_seq_rec *xlrec = (xl_seq_rec *) XLogRecGetData(record);
+	sequence_magic *sm;
+
+	if (info != XLOG_SEQ_LOG)
+		elog(PANIC, "seq_redo: unknown op code %u", info);
+
+	buffer = XLogInitBufferForRedo(record, 0);
+	page = BufferGetPage(buffer);
+
+	/*
+	 * We always reinit the page.  However, since this WAL record type is also
+	 * used for updating sequences, it's possible that a hot-standby backend
+	 * is examining the page concurrently; so we mustn't transiently trash the
+	 * buffer.  The solution is to build the correct new page contents in
+	 * local workspace and then memcpy into the buffer.  Then only bytes that
+	 * are supposed to change will change, even transiently. We must palloc
+	 * the local page for alignment reasons.
+	 */
+	localpage = (Page) palloc(BufferGetPageSize(buffer));
+
+	PageInit(localpage, BufferGetPageSize(buffer), sizeof(sequence_magic));
+	sm = (sequence_magic *) PageGetSpecialPointer(localpage);
+	sm->magic = SEQ_MAGIC;
+
+	item = (char *) xlrec + sizeof(xl_seq_rec);
+	itemsz = XLogRecGetDataLen(record) - sizeof(xl_seq_rec);
+
+	if (PageAddItem(localpage, item, itemsz, FirstOffsetNumber, false, false) == InvalidOffsetNumber)
+		elog(PANIC, "seq_redo: failed to add item to page");
+
+	PageSetLSN(localpage, lsn);
+
+	memcpy(page, localpage, BufferGetPageSize(buffer));
+	MarkBufferDirty(buffer);
+	UnlockReleaseBuffer(buffer);
+
+	pfree(localpage);
+}
+
+/*
+ * Mask a Sequence page before performing consistency checks on it.
+ */
+void
+seq_mask(char *page, BlockNumber blkno)
+{
+	mask_page_lsn_and_checksum(page);
+
+	mask_unused_space(page);
+}

src/bin/pg_waldump/rmgrdesc.c

@@ -24,7 +24,7 @@
 #include "access/xlog_internal.h"
 #include "catalog/storage_xlog.h"
 #include "commands/dbcommands_xlog.h"
-#include "commands/sequence.h"
+#include "commands/sequence_xlog.h"
 #include "commands/tablespace.h"
 #include "replication/message.h"
 #include "replication/origin.h"

src/include/commands/sequence.h

@@ -13,14 +13,10 @@
 #ifndef SEQUENCE_H
 #define SEQUENCE_H
 
-#include "access/xlogreader.h"
 #include "catalog/objectaddress.h"
 #include "fmgr.h"
-#include "lib/stringinfo.h"
 #include "nodes/parsenodes.h"
 #include "parser/parse_node.h"
-#include "storage/relfilelocator.h"
-
 
 typedef struct FormData_pg_sequence_data
 {
@@ -42,15 +38,6 @@ typedef FormData_pg_sequence_data *Form_pg_sequence_data;
 #define SEQ_COL_FIRSTCOL		SEQ_COL_LASTVAL
 #define SEQ_COL_LASTCOL			SEQ_COL_CALLED
 
-/* XLOG stuff */
-#define XLOG_SEQ_LOG			0x00
-
-typedef struct xl_seq_rec
-{
-	RelFileLocator locator;
-	/* SEQUENCE TUPLE DATA FOLLOWS AT THE END */
-} xl_seq_rec;
-
 extern int64 nextval_internal(Oid relid, bool check_permissions);
 extern Datum nextval(PG_FUNCTION_ARGS);
 extern List *sequence_options(Oid relid);
@@ -63,9 +50,4 @@ extern void ResetSequence(Oid seq_relid);
 extern void SetSequence(Oid relid, int64 next, bool is_called);
 extern void ResetSequenceCaches(void);
 
-extern void seq_redo(XLogReaderState *record);
-extern void seq_desc(StringInfo buf, XLogReaderState *record);
-extern const char *seq_identify(uint8 info);
-extern void seq_mask(char *page, BlockNumber blkno);
-
 #endif							/* SEQUENCE_H */

src/include/commands/sequence_xlog.h

@@ -0,0 +1,45 @@
+/*-------------------------------------------------------------------------
+ *
+ * sequence_xlog.h
+ *	  Sequence WAL definitions.
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/commands/sequence_xlog.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SEQUENCE_XLOG_H
+#define SEQUENCE_XLOG_H
+
+#include "access/xlogreader.h"
+#include "lib/stringinfo.h"
+
+/* Record identifier */
+#define XLOG_SEQ_LOG			0x00
+
+/*
+ * The "special area" of a sequence's buffer page looks like this.
+ */
+#define SEQ_MAGIC		0x1717
+
+typedef struct sequence_magic
+{
+	uint32		magic;
+} sequence_magic;
+
+/* Sequence WAL record */
+typedef struct xl_seq_rec
+{
+	RelFileLocator locator;
+	/* SEQUENCE TUPLE DATA FOLLOWS AT THE END */
+} xl_seq_rec;
+
+extern void seq_redo(XLogReaderState *record);
+extern void seq_desc(StringInfo buf, XLogReaderState *record);
+extern const char *seq_identify(uint8 info);
+extern void seq_mask(char *page, BlockNumber blkno);
+
+#endif							/* SEQUENCE_XLOG_H */