pg_visibility: Add pg_truncate_visibility_map function.

This requires some core changes as well so that we can properly
WAL-log the truncation.  Specifically, it changes the format of the
XLOG_SMGR_TRUNCATE WAL record, so bump XLOG_PAGE_MAGIC.

Patch by me, reviewed but not fully endorsed by Andres Freund.

2 files changed, 9 insertions, 1 deletions

diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index af2944c1b35..2627519ba08 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -31,7 +31,7 @@
 /*
  * Each page of XLOG file has a header like this:
  */
-#define XLOG_PAGE_MAGIC 0xD091	/* can be used as WAL version indicator */
+#define XLOG_PAGE_MAGIC 0xD092	/* can be used as WAL version indicator */
 
 typedef struct XLogPageHeaderData
 {
diff --git a/src/include/catalog/storage_xlog.h b/src/include/catalog/storage_xlog.h
index 7207e8be727..500e663b5fb 100644
--- a/src/include/catalog/storage_xlog.h
+++ b/src/include/catalog/storage_xlog.h
@@ -36,10 +36,18 @@ typedef struct xl_smgr_create
 	ForkNumber	forkNum;
 } xl_smgr_create;
 
+/* flags for xl_smgr_truncate */
+#define SMGR_TRUNCATE_HEAP		0x0001
+#define SMGR_TRUNCATE_VM		0x0002
+#define SMGR_TRUNCATE_FSM		0x0004
+#define SMGR_TRUNCATE_ALL		\
+	(SMGR_TRUNCATE_HEAP|SMGR_TRUNCATE_VM|SMGR_TRUNCATE_FSM)
+
 typedef struct xl_smgr_truncate
 {
 	BlockNumber blkno;
 	RelFileNode rnode;
+	int			flags;
 } xl_smgr_truncate;
 
 extern void log_smgrcreate(RelFileNode *rnode, ForkNumber forkNum);