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

4 files changed, 84 insertions, 74 deletions

diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index f99acfd2b4b..64cb6278409 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -53,6 +53,7 @@ OBJS = \
 	schemacmds.o \
 	seclabel.o \
 	sequence.o \
+	sequence_xlog.o \
 	statscmds.o \
 	subscriptioncmds.o \
 	tablecmds.o \
diff --git a/src/backend/commands/meson.build b/src/backend/commands/meson.build
index 9f640ad4810..5fc35826b1c 100644
--- a/src/backend/commands/meson.build
+++ b/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',
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 8d671b7a29d..51567994126 100644
--- a/src/backend/commands/sequence.c
+++ b/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"
@@ -59,16 +58,6 @@
 #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
  * rely on the relcache, since it's only, well, a cache, and may decide to
@@ -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);
-}
diff --git a/src/backend/commands/sequence_xlog.c b/src/backend/commands/sequence_xlog.c
new file mode 100644
index 00000000000..ffbd9820416
--- /dev/null
+++ b/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);
+}