Set PD_ALL_VISIBLE and visibility map bits in COPY FREEZE

Make sure COPY FREEZE marks the pages as PD_ALL_VISIBLE and updates the
visibility map. Until now we only marked individual tuples as frozen,
but page-level flags were not updated, so the first VACUUM after the
COPY FREEZE had to rewrite the whole table.

This is a fairly old patch, and multiple people worked on it. The first
version was written by Jeff Janes, and then reworked by Pavan Deolasee
and Anastasia Lubennikova.

Author: Anastasia Lubennikova, Pavan Deolasee, Jeff Janes
Reviewed-by: Kuntal Ghosh, Jeff Janes, Tomas Vondra, Masahiko Sawada,
             Andres Freund, Ibrar Ahmed, Robert Haas, Tatsuro Ishii,
             Darafei Praliaskouski
Discussion: https://postgr.es/m/CABOikdN-ptGv0mZntrK2Q8OtfUuAjqaYMGmkdU1dCKFtUxVLrg@mail.gmail.com
Discussion: https://postgr.es/m/CAMkU%3D1w3osJJ2FneELhhNRLxfZitDgp9FPHee08NT2FQFmz_pQ%40mail.gmail.com

Author: tvondra

contrib/pg_visibility/expected/pg_visibility.out

@@ -179,6 +179,69 @@ select pg_truncate_visibility_map('test_partition');
 
 (1 row)
 
+-- test copy freeze
+create table copyfreeze (a int, b char(1500));
+-- load all rows via COPY FREEZE and ensure that all pages are set all-visible
+-- and all-frozen.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+commit;
+select * from pg_visibility_map('copyfreeze');
+ blkno | all_visible | all_frozen 
+-------+-------------+------------
+     0 | t           | t
+     1 | t           | t
+     2 | t           | t
+(3 rows)
+
+select * from pg_check_frozen('copyfreeze');
+ t_ctid 
+--------
+(0 rows)
+
+-- load half the rows via regular COPY and rest via COPY FREEZE. The pages
+-- which are touched by regular COPY must not be set all-visible/all-frozen. On
+-- the other hand, pages allocated by COPY FREEZE should be marked
+-- all-frozen/all-visible.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin;
+copy copyfreeze from stdin freeze;
+commit;
+select * from pg_visibility_map('copyfreeze');
+ blkno | all_visible | all_frozen 
+-------+-------------+------------
+     0 | f           | f
+     1 | f           | f
+     2 | t           | t
+(3 rows)
+
+select * from pg_check_frozen('copyfreeze');
+ t_ctid 
+--------
+(0 rows)
+
+-- Try a mix of regular COPY and COPY FREEZE.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+copy copyfreeze from stdin;
+copy copyfreeze from stdin freeze;
+commit;
+select * from pg_visibility_map('copyfreeze');
+ blkno | all_visible | all_frozen 
+-------+-------------+------------
+     0 | t           | t
+     1 | f           | f
+     2 | t           | t
+(3 rows)
+
+select * from pg_check_frozen('copyfreeze');
+ t_ctid 
+--------
+(0 rows)
+
 -- cleanup
 drop table test_partitioned;
 drop view test_view;
@@ -188,3 +251,4 @@ drop server dummy_server;
 drop foreign data wrapper dummy;
 drop materialized view matview_visibility_test;
 drop table regular_table;
+drop table copyfreeze;

contrib/pg_visibility/sql/pg_visibility.sql

@@ -94,6 +94,82 @@ select count(*) > 0 from pg_visibility_map_summary('test_partition');
 select * from pg_check_frozen('test_partition'); -- hopefully none
 select pg_truncate_visibility_map('test_partition');
 
+-- test copy freeze
+create table copyfreeze (a int, b char(1500));
+
+-- load all rows via COPY FREEZE and ensure that all pages are set all-visible
+-- and all-frozen.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+1	'1'
+2	'2'
+3	'3'
+4	'4'
+5	'5'
+6	'6'
+7	'7'
+8	'8'
+9	'9'
+10	'10'
+11	'11'
+12	'12'
+\.
+commit;
+select * from pg_visibility_map('copyfreeze');
+select * from pg_check_frozen('copyfreeze');
+
+-- load half the rows via regular COPY and rest via COPY FREEZE. The pages
+-- which are touched by regular COPY must not be set all-visible/all-frozen. On
+-- the other hand, pages allocated by COPY FREEZE should be marked
+-- all-frozen/all-visible.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin;
+1	'1'
+2	'2'
+3	'3'
+4	'4'
+5	'5'
+6	'6'
+\.
+copy copyfreeze from stdin freeze;
+7	'7'
+8	'8'
+9	'9'
+10	'10'
+11	'11'
+12	'12'
+\.
+commit;
+select * from pg_visibility_map('copyfreeze');
+select * from pg_check_frozen('copyfreeze');
+
+-- Try a mix of regular COPY and COPY FREEZE.
+begin;
+truncate copyfreeze;
+copy copyfreeze from stdin freeze;
+1	'1'
+2	'2'
+3	'3'
+4	'4'
+5	'5'
+\.
+copy copyfreeze from stdin;
+6	'6'
+\.
+copy copyfreeze from stdin freeze;
+7	'7'
+8	'8'
+9	'9'
+10	'10'
+11	'11'
+12	'12'
+\.
+commit;
+select * from pg_visibility_map('copyfreeze');
+select * from pg_check_frozen('copyfreeze');
+
 -- cleanup
 drop table test_partitioned;
 drop view test_view;
@@ -103,3 +179,4 @@ drop server dummy_server;
 drop foreign data wrapper dummy;
 drop materialized view matview_visibility_test;
 drop table regular_table;
+drop table copyfreeze;

src/backend/access/heap/heapam.c

@@ -2121,6 +2121,7 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 	int			ndone;
 	PGAlignedBlock scratch;
 	Page		page;
+	Buffer		vmbuffer = InvalidBuffer;
 	bool		needwal;
 	Size		saveFreeSpace;
 	bool		need_tuple_data = RelationIsLogicallyLogged(relation);
@@ -2175,21 +2176,30 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 	while (ndone < ntuples)
 	{
 		Buffer		buffer;
-		Buffer		vmbuffer = InvalidBuffer;
+		bool		starting_with_empty_page;
 		bool		all_visible_cleared = false;
+		bool		all_frozen_set = false;
 		int			nthispage;
 
 		CHECK_FOR_INTERRUPTS();
 
 		/*
 		 * Find buffer where at least the next tuple will fit.  If the page is
 		 * all-visible, this will also pin the requisite visibility map page.
+		 *
+		 * Also pin visibility map page if COPY FREEZE inserts tuples into an
+		 * empty page. See all_frozen_set below.
 		 */
 		buffer = RelationGetBufferForTuple(relation, heaptuples[ndone]->t_len,
 										   InvalidBuffer, options, bistate,
 										   &vmbuffer, NULL);
 		page = BufferGetPage(buffer);
 
+		starting_with_empty_page = PageGetMaxOffsetNumber(page) == 0;
+
+		if (starting_with_empty_page && (options & HEAP_INSERT_FROZEN))
+			all_frozen_set = true;
+
 		/* NO EREPORT(ERROR) from here till changes are logged */
 		START_CRIT_SECTION();
 
@@ -2223,14 +2233,23 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 				log_heap_new_cid(relation, heaptup);
 		}
 
-		if (PageIsAllVisible(page))
+		/*
+		 * If the page is all visible, need to clear that, unless we're only
+		 * going to add further frozen rows to it.
+		 *
+		 * If we're only adding already frozen rows to a previously empty
+		 * page, mark it as all-visible.
+		 */
+		if (PageIsAllVisible(page) && !(options & HEAP_INSERT_FROZEN))
 		{
 			all_visible_cleared = true;
 			PageClearAllVisible(page);
 			visibilitymap_clear(relation,
 								BufferGetBlockNumber(buffer),
 								vmbuffer, VISIBILITYMAP_VALID_BITS);
 		}
+		else if (all_frozen_set)
+			PageSetAllVisible(page);
 
 		/*
 		 * XXX Should we set PageSetPrunable on this page ? See heap_insert()
@@ -2254,8 +2273,7 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 			 * If the page was previously empty, we can reinit the page
 			 * instead of restoring the whole thing.
 			 */
-			init = (ItemPointerGetOffsetNumber(&(heaptuples[ndone]->t_self)) == FirstOffsetNumber &&
-					PageGetMaxOffsetNumber(page) == FirstOffsetNumber + nthispage - 1);
+			init = starting_with_empty_page;
 
 			/* allocate xl_heap_multi_insert struct from the scratch area */
 			xlrec = (xl_heap_multi_insert *) scratchptr;
@@ -2273,7 +2291,15 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 			/* the rest of the scratch space is used for tuple data */
 			tupledata = scratchptr;
 
-			xlrec->flags = all_visible_cleared ? XLH_INSERT_ALL_VISIBLE_CLEARED : 0;
+			/* check that the mutually exclusive flags are not both set */
+			Assert (!(all_visible_cleared && all_frozen_set));
+
+			xlrec->flags = 0;
+			if (all_visible_cleared)
+				xlrec->flags = XLH_INSERT_ALL_VISIBLE_CLEARED;
+			if (all_frozen_set)
+				xlrec->flags = XLH_INSERT_ALL_FROZEN_SET;
+
 			xlrec->ntuples = nthispage;
 
 			/*
@@ -2347,13 +2373,40 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 
 		END_CRIT_SECTION();
 
-		UnlockReleaseBuffer(buffer);
-		if (vmbuffer != InvalidBuffer)
-			ReleaseBuffer(vmbuffer);
+		/*
+		 * If we've frozen everything on the page, update the visibilitymap.
+		 * We're already holding pin on the vmbuffer.
+		 */
+		if (all_frozen_set)
+		{
+			Assert(PageIsAllVisible(page));
+			Assert(visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer));
 
+			/*
+			 * It's fine to use InvalidTransactionId here - this is only used
+			 * when HEAP_INSERT_FROZEN is specified, which intentionally
+			 * violates visibility rules.
+			 */
+			visibilitymap_set(relation, BufferGetBlockNumber(buffer), buffer,
+							  InvalidXLogRecPtr, vmbuffer,
+							  InvalidTransactionId,
+							  VISIBILITYMAP_ALL_VISIBLE | VISIBILITYMAP_ALL_FROZEN);
+		}
+
+		UnlockReleaseBuffer(buffer);
 		ndone += nthispage;
+
+		/*
+		 * NB: Only release vmbuffer after inserting all tuples - it's fairly
+		 * likely that we'll insert into subsequent heap pages that are likely
+		 * to use the same vm page.
+		 */
 	}
 
+	/* We're done with inserting all tuples, so release the last vmbuffer. */
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+
 	/*
 	 * We're done with the actual inserts.  Check for conflicts again, to
 	 * ensure that all rw-conflicts in to these inserts are detected.  Without
@@ -8725,6 +8778,10 @@ heap_xlog_insert(XLogReaderState *record)
 		if (xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED)
 			PageClearAllVisible(page);
 
+		/* XLH_INSERT_ALL_FROZEN_SET implies that all tuples are visible */
+		if (xlrec->flags & XLH_INSERT_ALL_FROZEN_SET)
+			PageSetAllVisible(page);
+
 		MarkBufferDirty(buffer);
 	}
 	if (BufferIsValid(buffer))
@@ -8775,6 +8832,10 @@ heap_xlog_multi_insert(XLogReaderState *record)
 
 	XLogRecGetBlockTag(record, 0, &rnode, NULL, &blkno);
 
+	/* check that the mutually exclusive flags are not both set */
+	Assert (!((xlrec->flags & XLH_INSERT_ALL_VISIBLE_CLEARED) &&
+			  (xlrec->flags & XLH_INSERT_ALL_FROZEN_SET)));
+
 	/*
 	 * The visibility map may need to be fixed even if the heap page is
 	 * already up-to-date.

src/backend/access/heap/hio.c

@@ -433,6 +433,14 @@ RelationGetBufferForTuple(Relation relation, Size len,
 			buffer = ReadBufferBI(relation, targetBlock, RBM_NORMAL, bistate);
 			if (PageIsAllVisible(BufferGetPage(buffer)))
 				visibilitymap_pin(relation, targetBlock, vmbuffer);
+
+			/*
+			 * If the page is empty, pin vmbuffer to set all_frozen bit later.
+			 */
+			if ((options & HEAP_INSERT_FROZEN) &&
+				(PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0))
+				visibilitymap_pin(relation, targetBlock, vmbuffer);
+
 			LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
 		}
 		else if (otherBlock == targetBlock)
@@ -619,6 +627,15 @@ RelationGetBufferForTuple(Relation relation, Size len,
 	PageInit(page, BufferGetPageSize(buffer), 0);
 	MarkBufferDirty(buffer);
 
+	/*
+	 * The page is empty, pin vmbuffer to set all_frozen bit.
+	 */
+	if (options & HEAP_INSERT_FROZEN)
+	{
+		Assert(PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0);
+		visibilitymap_pin(relation, BufferGetBlockNumber(buffer), vmbuffer);
+	}
+
 	/*
 	 * Release the file-extension lock; it's now OK for someone else to extend
 	 * the relation some more.

src/include/access/heapam_xlog.h

@@ -69,6 +69,9 @@
 #define XLH_INSERT_CONTAINS_NEW_TUPLE			(1<<3)
 #define XLH_INSERT_ON_TOAST_RELATION			(1<<4)
 
+/* all_frozen_set always implies all_visible_set */
+#define XLH_INSERT_ALL_FROZEN_SET				(1<<5)
+
 /*
  * xl_heap_update flag values, 8 bits are available.
  */