Change the format of the VM fork to add a second bit per page.

The new bit indicates whether every tuple on the page is already frozen.
It is cleared only when the all-visible bit is cleared, and it can be
set only when we vacuum a page and find that every tuple on that page is
both visible to every transaction and in no need of any future
vacuuming.

A future commit will use this new bit to optimize away full-table scans
that would otherwise be triggered by XID wraparound considerations.  A
page which is merely all-visible must still be scanned in that case, but
a page which is all-frozen need not be.  This commit does not attempt
that optimization, although that optimization is the goal here.  It
seems better to get the basic infrastructure in place first.

Per discussion, it's very desirable for pg_upgrade to automatically
migrate existing VM forks from the old format to the new format.  That,
too, will be handled in a follow-on patch.

Masahiko Sawada, reviewed by Kyotaro Horiguchi, Fujii Masao, Amit
Kapila, Simon Riggs, Andres Freund, and others, and substantially
revised by me.

5 files changed, 32 insertions, 8 deletions

diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index a427df5eaa1..b3a595c67e9 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -170,6 +170,7 @@ extern bool heap_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
 				  TransactionId cutoff_multi);
 extern bool heap_tuple_needs_freeze(HeapTupleHeader tuple, TransactionId cutoff_xid,
 						MultiXactId cutoff_multi, Buffer buf);
+extern bool heap_tuple_needs_eventual_freeze(HeapTupleHeader tuple);
 
 extern Oid	simple_heap_insert(Relation relation, HeapTuple tup);
 extern void simple_heap_delete(Relation relation, ItemPointer tid);
diff --git a/src/include/access/heapam_xlog.h b/src/include/access/heapam_xlog.h
index f77489bb78d..ad30217cfbf 100644
--- a/src/include/access/heapam_xlog.h
+++ b/src/include/access/heapam_xlog.h
@@ -320,9 +320,10 @@ typedef struct xl_heap_freeze_page
 typedef struct xl_heap_visible
 {
 	TransactionId cutoff_xid;
+	uint8		flags;
 } xl_heap_visible;
 
-#define SizeOfHeapVisible (offsetof(xl_heap_visible, cutoff_xid) + sizeof(TransactionId))
+#define SizeOfHeapVisible (offsetof(xl_heap_visible, flags) + sizeof(uint8))
 
 typedef struct xl_heap_new_cid
 {
@@ -389,6 +390,6 @@ extern bool heap_prepare_freeze_tuple(HeapTupleHeader tuple,
 extern void heap_execute_freeze_tuple(HeapTupleHeader tuple,
 						  xl_heap_freeze_tuple *xlrec_tp);
 extern XLogRecPtr log_heap_visible(RelFileNode rnode, Buffer heap_buffer,
-				 Buffer vm_buffer, TransactionId cutoff_xid);
+				 Buffer vm_buffer, TransactionId cutoff_xid, uint8 flags);
 
 #endif   /* HEAPAM_XLOG_H */
diff --git a/src/include/access/visibilitymap.h b/src/include/access/visibilitymap.h
index d447daff7a5..b8dc54c55d2 100644
--- a/src/include/access/visibilitymap.h
+++ b/src/include/access/visibilitymap.h
@@ -19,15 +19,30 @@
 #include "storage/buf.h"
 #include "utils/relcache.h"
 
+#define BITS_PER_HEAPBLOCK 2
+#define HEAPBLOCKS_PER_BYTE (BITS_PER_BYTE / BITS_PER_HEAPBLOCK)
+
+/* Flags for bit map */
+#define VISIBILITYMAP_ALL_VISIBLE	0x01
+#define VISIBILITYMAP_ALL_FROZEN	0x02
+#define VISIBILITYMAP_VALID_BITS	0x03 /* OR of all valid visiblitymap flags bits */
+
+/* Macros for visibilitymap test */
+#define VM_ALL_VISIBLE(r, b, v) \
+	((visibilitymap_get_status((r), (b), (v)) & VISIBILITYMAP_ALL_VISIBLE) != 0)
+#define VM_ALL_FROZEN(r, b, v) \
+	((visibilitymap_get_status((r), (b), (v)) & VISIBILITYMAP_ALL_FROZEN) != 0)
+
 extern void visibilitymap_clear(Relation rel, BlockNumber heapBlk,
 					Buffer vmbuf);
 extern void visibilitymap_pin(Relation rel, BlockNumber heapBlk,
 				  Buffer *vmbuf);
 extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf);
 extern void visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
-				  XLogRecPtr recptr, Buffer vmBuf, TransactionId cutoff_xid);
-extern bool visibilitymap_test(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
-extern BlockNumber visibilitymap_count(Relation rel);
+							  XLogRecPtr recptr, Buffer vmBuf, TransactionId cutoff_xid,
+							  uint8 flags);
+extern uint8 visibilitymap_get_status(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
+extern void visibilitymap_count(Relation rel, BlockNumber *all_visible, BlockNumber *all_frozen);
 extern void visibilitymap_truncate(Relation rel, BlockNumber nheapblocks);
 
 #endif   /* VISIBILITYMAP_H */
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index aff12d353c3..6795834912a 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201602221
+#define CATALOG_VERSION_NO	201603011
 
 #endif
diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h
index 2ce3be765c0..0b023b3d853 100644
--- a/src/include/storage/bufpage.h
+++ b/src/include/storage/bufpage.h
@@ -178,8 +178,10 @@ typedef PageHeaderData *PageHeader;
 										 * tuple? */
 #define PD_ALL_VISIBLE		0x0004		/* all tuples on page are visible to
 										 * everyone */
+#define PD_ALL_FROZEN		0x0008		/* all tuples on page are completely
+										   frozen */
 
-#define PD_VALID_FLAG_BITS	0x0007		/* OR of all valid pd_flags bits */
+#define PD_VALID_FLAG_BITS	0x000F		/* OR of all valid pd_flags bits */
 
 /*
  * Page layout version number 0 is for pre-7.3 Postgres releases.
@@ -367,7 +369,12 @@ typedef PageHeaderData *PageHeader;
 #define PageSetAllVisible(page) \
 	(((PageHeader) (page))->pd_flags |= PD_ALL_VISIBLE)
 #define PageClearAllVisible(page) \
-	(((PageHeader) (page))->pd_flags &= ~PD_ALL_VISIBLE)
+	(((PageHeader) (page))->pd_flags &= ~(PD_ALL_VISIBLE | PD_ALL_FROZEN))
+
+#define PageIsAllFrozen(page) \
+	(((PageHeader) (page))->pd_flags & PD_ALL_FROZEN)
+#define PageSetAllFrozen(page) \
+	(((PageHeader) (page))->pd_flags |= PD_ALL_FROZEN)
 
 #define PageIsPrunable(page, oldestxmin) \
 ( \