Fix COPY FREEZE with CLOBBER_CACHE_ALWAYS

This adds code omitted from commit 7db0cd2 by accident, which had
two consequences. Firstly, only rows inserted by heap_multi_insert were
frozen as expected when running COPY FREEZE, while heap_insert left
rows unfrozen. That however includes rows in TOAST tables, so a lot of
data might have been left unfrozen. Secondly, page might have been left
partially empty after relcache invalidation.

This addresses both of those issues.

Discussion: https://postgr.es/m/CABOikdN-ptGv0mZntrK2Q8OtfUuAjqaYMGmkdU1dCKFtUxVLrg@mail.gmail.com

Author: tvondra

src/backend/access/heap/heapam.c

@@ -1880,8 +1880,12 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 	TransactionId xid = GetCurrentTransactionId();
 	HeapTuple	heaptup;
 	Buffer		buffer;
+	Page		page = NULL;
 	Buffer		vmbuffer = InvalidBuffer;
+	bool		starting_with_empty_page;
 	bool		all_visible_cleared = false;
+	bool		all_frozen_set = false;
+	uint8		vmstatus = 0;
 
 	/*
 	 * Fill in tuple header fields and toast the tuple if necessary.
@@ -1894,11 +1898,36 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 	/*
 	 * Find buffer to insert this tuple into.  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, heaptup->t_len,
 									   InvalidBuffer, options, bistate,
 									   &vmbuffer, NULL);
 
+
+	/*
+	 * If we're inserting frozen entry into an empty page,
+	 * set visibility map bits and PageAllVisible() hint.
+	 *
+	 * If we're inserting frozen entry into already all_frozen page,
+	 * preserve this state.
+	 */
+	if (options & HEAP_INSERT_FROZEN)
+	{
+		page = BufferGetPage(buffer);
+
+		starting_with_empty_page = PageGetMaxOffsetNumber(page) == 0;
+
+		if (visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer))
+			vmstatus = visibilitymap_get_status(relation,
+								 BufferGetBlockNumber(buffer), &vmbuffer);
+
+		if ((starting_with_empty_page || vmstatus & VISIBILITYMAP_ALL_FROZEN))
+			all_frozen_set = true;
+	}
+
 	/*
 	 * We're about to do the actual insert -- but check for conflict first, to
 	 * avoid possibly having to roll back work we've just done.
@@ -1922,14 +1951,28 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 	RelationPutHeapTuple(relation, buffer, heaptup,
 						 (options & HEAP_INSERT_SPECULATIVE) != 0);
 
-	if (PageIsAllVisible(BufferGetPage(buffer)))
+	/*
+	 * 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 page that was empty or
+	 * marked as all visible, mark it as all-visible.
+	 */
+	if (PageIsAllVisible(BufferGetPage(buffer)) && !(options & HEAP_INSERT_FROZEN))
 	{
 		all_visible_cleared = true;
 		PageClearAllVisible(BufferGetPage(buffer));
 		visibilitymap_clear(relation,
 							ItemPointerGetBlockNumber(&(heaptup->t_self)),
 							vmbuffer, VISIBILITYMAP_VALID_BITS);
 	}
+	else if (all_frozen_set)
+	{
+		/* We only ever set all_frozen_set after reading the page. */
+		Assert(page);
+
+		PageSetAllVisible(page);
+	}
 
 	/*
 	 * XXX Should we set PageSetPrunable on this page ?
@@ -1977,6 +2020,8 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 		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;
 		if (options & HEAP_INSERT_SPECULATIVE)
 			xlrec.flags |= XLH_INSERT_IS_SPECULATIVE;
 		Assert(ItemPointerGetBlockNumber(&heaptup->t_self) == BufferGetBlockNumber(buffer));
@@ -2025,6 +2070,29 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 
 	END_CRIT_SECTION();
 
+	/*
+	 * If we've frozen everything on the page, update the visibilitymap.
+	 * We're already holding pin on the vmbuffer.
+	 *
+	 * No need to update the visibilitymap if it had all_frozen bit set
+	 * before this insertion.
+	 */
+	if (all_frozen_set && ((vmstatus & VISIBILITYMAP_ALL_FROZEN) == 0))
+	{
+		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);
 	if (vmbuffer != InvalidBuffer)
 		ReleaseBuffer(vmbuffer);
@@ -8708,6 +8776,10 @@ heap_xlog_insert(XLogReaderState *record)
 	ItemPointerSetBlockNumber(&target_tid, blkno);
 	ItemPointerSetOffsetNumber(&target_tid, xlrec->offnum);
 
+	/* 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.
@@ -8925,6 +8997,10 @@ heap_xlog_multi_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))

src/backend/access/heap/hio.c

@@ -396,19 +396,19 @@ RelationGetBufferForTuple(Relation relation, Size len,
 		 * target.
 		 */
 		targetBlock = GetPageWithFreeSpace(relation, len + saveFreeSpace);
+	}
 
-		/*
-		 * If the FSM knows nothing of the rel, try the last page before we
-		 * give up and extend.  This avoids one-tuple-per-page syndrome during
-		 * bootstrapping or in a recently-started system.
-		 */
-		if (targetBlock == InvalidBlockNumber)
-		{
-			BlockNumber nblocks = RelationGetNumberOfBlocks(relation);
+	/*
+	 * If the FSM knows nothing of the rel, try the last page before we
+	 * give up and extend.  This avoids one-tuple-per-page syndrome during
+	 * bootstrapping or in a recently-started system.
+	 */
+	if (targetBlock == InvalidBlockNumber)
+	{
+		BlockNumber nblocks = RelationGetNumberOfBlocks(relation);
 
-			if (nblocks > 0)
-				targetBlock = nblocks - 1;
-		}
+		if (nblocks > 0)
+			targetBlock = nblocks - 1;
 	}
 
 loop: