Merge prune, freeze and vacuum WAL record formats

The new combined WAL record is now used for pruning, freezing and 2nd
pass of vacuum. This is in preparation for changing VACUUM to write a
combined prune+freeze record per page, instead of separate two
records. The new WAL record format now supports that, but the code
still always writes separate records for pruning and freezing.

This reserves separate XLOG_HEAP2_* info codes for when the pruning
record is emitted for on-access pruning or VACUUM, per Peter
Geoghegan's suggestion. The record format is identical, but having
separate info codes makes it easier analyze pruning and vacuuming with
pg_waldump.

The function to emit the new WAL record, log_heap_prune_and_freeze(),
is in pruneheap.c. The existing heap_log_freeze_plan() and its
subroutines are moved to pruneheap.c without changes, to keep them
together with log_heap_prune_and_freeze().

Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/CAAKRu_azf-zH%3DDgVbquZ3tFWjMY1w5pO8m-TXJaMdri8z3933g@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAAKRu_b2oE4GL%3Dq4g9mcByS9yT7wTQvEH9OLpabj28e%2BWKFi2A@mail.gmail.com

1 files changed, 112 insertions, 361 deletions

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 34bc60f625f..cc67dd813d2 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -91,9 +91,6 @@ static void compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask,
 static TM_Result heap_lock_updated_tuple(Relation rel, HeapTuple tuple,
 										 ItemPointer ctid, TransactionId xid,
 										 LockTupleMode mode);
-static int	heap_log_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
-								 xl_heap_freeze_plan *plans_out,
-								 OffsetNumber *offsets_out);
 static void GetMultiXactIdHintBits(MultiXactId multi, uint16 *new_infomask,
 								   uint16 *new_infomask2);
 static TransactionId MultiXactIdGetUpdateXid(TransactionId xmax,
@@ -6746,180 +6743,19 @@ heap_freeze_execute_prepared(Relation rel, Buffer buffer,
 	/* Now WAL-log freezing if necessary */
 	if (RelationNeedsWAL(rel))
 	{
-		xl_heap_freeze_plan plans[MaxHeapTuplesPerPage];
-		OffsetNumber offsets[MaxHeapTuplesPerPage];
-		int			nplans;
-		xl_heap_freeze_page xlrec;
-		XLogRecPtr	recptr;
-
-		/* Prepare deduplicated representation for use in WAL record */
-		nplans = heap_log_freeze_plan(tuples, ntuples, plans, offsets);
-
-		xlrec.snapshotConflictHorizon = snapshotConflictHorizon;
-		xlrec.isCatalogRel = RelationIsAccessibleInLogicalDecoding(rel);
-		xlrec.nplans = nplans;
-
-		XLogBeginInsert();
-		XLogRegisterData((char *) &xlrec, SizeOfHeapFreezePage);
-
-		/*
-		 * The freeze plan array and offset array are not actually in the
-		 * buffer, but pretend that they are.  When XLogInsert stores the
-		 * whole buffer, the arrays need not be stored too.
-		 */
-		XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
-		XLogRegisterBufData(0, (char *) plans,
-							nplans * sizeof(xl_heap_freeze_plan));
-		XLogRegisterBufData(0, (char *) offsets,
-							ntuples * sizeof(OffsetNumber));
-
-		recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_FREEZE_PAGE);
-
-		PageSetLSN(page, recptr);
+		log_heap_prune_and_freeze(rel, buffer, snapshotConflictHorizon,
+								  false,	/* no cleanup lock required */
+								  PRUNE_VACUUM_SCAN,
+								  tuples, ntuples,
+								  NULL, 0,	/* redirected */
+								  NULL, 0,	/* dead */
+								  NULL, 0); /* unused */
 	}
 
 	END_CRIT_SECTION();
 }
 
 /*
- * Comparator used to deduplicate XLOG_HEAP2_FREEZE_PAGE freeze plans
- */
-static int
-heap_log_freeze_cmp(const void *arg1, const void *arg2)
-{
-	HeapTupleFreeze *frz1 = (HeapTupleFreeze *) arg1;
-	HeapTupleFreeze *frz2 = (HeapTupleFreeze *) arg2;
-
-	if (frz1->xmax < frz2->xmax)
-		return -1;
-	else if (frz1->xmax > frz2->xmax)
-		return 1;
-
-	if (frz1->t_infomask2 < frz2->t_infomask2)
-		return -1;
-	else if (frz1->t_infomask2 > frz2->t_infomask2)
-		return 1;
-
-	if (frz1->t_infomask < frz2->t_infomask)
-		return -1;
-	else if (frz1->t_infomask > frz2->t_infomask)
-		return 1;
-
-	if (frz1->frzflags < frz2->frzflags)
-		return -1;
-	else if (frz1->frzflags > frz2->frzflags)
-		return 1;
-
-	/*
-	 * heap_log_freeze_eq would consider these tuple-wise plans to be equal.
-	 * (So the tuples will share a single canonical freeze plan.)
-	 *
-	 * We tiebreak on page offset number to keep each freeze plan's page
-	 * offset number array individually sorted. (Unnecessary, but be tidy.)
-	 */
-	if (frz1->offset < frz2->offset)
-		return -1;
-	else if (frz1->offset > frz2->offset)
-		return 1;
-
-	Assert(false);
-	return 0;
-}
-
-/*
- * Compare fields that describe actions required to freeze tuple with caller's
- * open plan.  If everything matches then the frz tuple plan is equivalent to
- * caller's plan.
- */
-static inline bool
-heap_log_freeze_eq(xl_heap_freeze_plan *plan, HeapTupleFreeze *frz)
-{
-	if (plan->xmax == frz->xmax &&
-		plan->t_infomask2 == frz->t_infomask2 &&
-		plan->t_infomask == frz->t_infomask &&
-		plan->frzflags == frz->frzflags)
-		return true;
-
-	/* Caller must call heap_log_freeze_new_plan again for frz */
-	return false;
-}
-
-/*
- * Start new plan initialized using tuple-level actions.  At least one tuple
- * will have steps required to freeze described by caller's plan during REDO.
- */
-static inline void
-heap_log_freeze_new_plan(xl_heap_freeze_plan *plan, HeapTupleFreeze *frz)
-{
-	plan->xmax = frz->xmax;
-	plan->t_infomask2 = frz->t_infomask2;
-	plan->t_infomask = frz->t_infomask;
-	plan->frzflags = frz->frzflags;
-	plan->ntuples = 1;			/* for now */
-}
-
-/*
- * Deduplicate tuple-based freeze plans so that each distinct set of
- * processing steps is only stored once in XLOG_HEAP2_FREEZE_PAGE records.
- * Called during original execution of freezing (for logged relations).
- *
- * Return value is number of plans set in *plans_out for caller.  Also writes
- * an array of offset numbers into *offsets_out output argument for caller
- * (actually there is one array per freeze plan, but that's not of immediate
- * concern to our caller).
- */
-static int
-heap_log_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
-					 xl_heap_freeze_plan *plans_out,
-					 OffsetNumber *offsets_out)
-{
-	int			nplans = 0;
-
-	/* Sort tuple-based freeze plans in the order required to deduplicate */
-	qsort(tuples, ntuples, sizeof(HeapTupleFreeze), heap_log_freeze_cmp);
-
-	for (int i = 0; i < ntuples; i++)
-	{
-		HeapTupleFreeze *frz = tuples + i;
-
-		if (i == 0)
-		{
-			/* New canonical freeze plan starting with first tup */
-			heap_log_freeze_new_plan(plans_out, frz);
-			nplans++;
-		}
-		else if (heap_log_freeze_eq(plans_out, frz))
-		{
-			/* tup matches open canonical plan -- include tup in it */
-			Assert(offsets_out[i - 1] < frz->offset);
-			plans_out->ntuples++;
-		}
-		else
-		{
-			/* Tup doesn't match current plan -- done with it now */
-			plans_out++;
-
-			/* New canonical freeze plan starting with this tup */
-			heap_log_freeze_new_plan(plans_out, frz);
-			nplans++;
-		}
-
-		/*
-		 * Save page offset number in dedicated buffer in passing.
-		 *
-		 * REDO routine relies on the record's offset numbers array grouping
-		 * offset numbers by freeze plan.  The sort order within each grouping
-		 * is ascending offset number order, just to keep things tidy.
-		 */
-		offsets_out[i] = frz->offset;
-	}
-
-	Assert(nplans > 0 && nplans <= ntuples);
-
-	return nplans;
-}
-
-/*
  * heap_freeze_tuple
  *		Freeze tuple in place, without WAL logging.
  *
@@ -7892,10 +7728,10 @@ heap_index_delete_tuples(Relation rel, TM_IndexDeleteOp *delstate)
 			 * must have considered the original tuple header as part of
 			 * generating its own snapshotConflictHorizon value.
 			 *
-			 * Relying on XLOG_HEAP2_PRUNE records like this is the same
-			 * strategy that index vacuuming uses in all cases.  Index VACUUM
-			 * WAL records don't even have a snapshotConflictHorizon field of
-			 * their own for this reason.
+			 * Relying on XLOG_HEAP2_PRUNE_VACUUM_SCAN records like this is
+			 * the same strategy that index vacuuming uses in all cases. Index
+			 * VACUUM WAL records don't even have a snapshotConflictHorizon
+			 * field of their own for this reason.
 			 */
 			if (!ItemIdIsNormal(lp))
 				break;
@@ -8753,162 +8589,149 @@ ExtractReplicaIdentity(Relation relation, HeapTuple tp, bool key_required,
 }
 
 /*
- * Handles XLOG_HEAP2_PRUNE record type.
- *
- * Acquires a full cleanup lock.
+ * Replay XLOG_HEAP2_PRUNE_* records.
  */
 static void
-heap_xlog_prune(XLogReaderState *record)
+heap_xlog_prune_freeze(XLogReaderState *record)
 {
 	XLogRecPtr	lsn = record->EndRecPtr;
-	xl_heap_prune *xlrec = (xl_heap_prune *) XLogRecGetData(record);
+	char	   *maindataptr = XLogRecGetData(record);
+	xl_heap_prune xlrec;
 	Buffer		buffer;
 	RelFileLocator rlocator;
 	BlockNumber blkno;
 	XLogRedoAction action;
 
 	XLogRecGetBlockTag(record, 0, &rlocator, NULL, &blkno);
+	memcpy(&xlrec, maindataptr, SizeOfHeapPrune);
+	maindataptr += SizeOfHeapPrune;
 
 	/*
-	 * We're about to remove tuples. In Hot Standby mode, ensure that there's
-	 * no queries running for which the removed tuples are still visible.
+	 * We will take an ordinary exclusive lock or a cleanup lock depending on
+	 * whether the XLHP_CLEANUP_LOCK flag is set.  With an ordinary exclusive
+	 * lock, we better not be doing anything that requires moving existing
+	 * tuple data.
 	 */
-	if (InHotStandby)
-		ResolveRecoveryConflictWithSnapshot(xlrec->snapshotConflictHorizon,
-											xlrec->isCatalogRel,
-											rlocator);
+	Assert((xlrec.flags & XLHP_CLEANUP_LOCK) != 0 ||
+		   (xlrec.flags & (XLHP_HAS_REDIRECTIONS | XLHP_HAS_DEAD_ITEMS)) == 0);
 
 	/*
-	 * If we have a full-page image, restore it (using a cleanup lock) and
-	 * we're done.
+	 * We are about to remove and/or freeze tuples.  In Hot Standby mode,
+	 * ensure that there are no queries running for which the removed tuples
+	 * are still visible or which still consider the frozen xids as running.
+	 * The conflict horizon XID comes after xl_heap_prune.
 	 */
-	action = XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, true,
+	if ((xlrec.flags & XLHP_HAS_CONFLICT_HORIZON) != 0)
+	{
+		TransactionId snapshot_conflict_horizon;
+
+		/* memcpy() because snapshot_conflict_horizon is stored unaligned */
+		memcpy(&snapshot_conflict_horizon, maindataptr, sizeof(TransactionId));
+		maindataptr += sizeof(TransactionId);
+
+		if (InHotStandby)
+			ResolveRecoveryConflictWithSnapshot(snapshot_conflict_horizon,
+												(xlrec.flags & XLHP_IS_CATALOG_REL) != 0,
+												rlocator);
+	}
+
+	/*
+	 * If we have a full-page image, restore it and we're done.
+	 */
+	action = XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL,
+										   (xlrec.flags & XLHP_CLEANUP_LOCK) != 0,
 										   &buffer);
 	if (action == BLK_NEEDS_REDO)
 	{
 		Page		page = (Page) BufferGetPage(buffer);
-		OffsetNumber *end;
 		OffsetNumber *redirected;
 		OffsetNumber *nowdead;
 		OffsetNumber *nowunused;
 		int			nredirected;
 		int			ndead;
 		int			nunused;
+		int			nplans;
 		Size		datalen;
+		xlhp_freeze_plan *plans;
+		OffsetNumber *frz_offsets;
+		char	   *dataptr = XLogRecGetBlockData(record, 0, &datalen);
 
-		redirected = (OffsetNumber *) XLogRecGetBlockData(record, 0, &datalen);
-
-		nredirected = xlrec->nredirected;
-		ndead = xlrec->ndead;
-		end = (OffsetNumber *) ((char *) redirected + datalen);
-		nowdead = redirected + (nredirected * 2);
-		nowunused = nowdead + ndead;
-		nunused = (end - nowunused);
-		Assert(nunused >= 0);
-
-		/* Update all line pointers per the record, and repair fragmentation */
-		heap_page_prune_execute(buffer,
-								redirected, nredirected,
-								nowdead, ndead,
-								nowunused, nunused);
+		heap_xlog_deserialize_prune_and_freeze(dataptr, xlrec.flags,
+											   &nplans, &plans, &frz_offsets,
+											   &nredirected, &redirected,
+											   &ndead, &nowdead,
+											   &nunused, &nowunused);
 
 		/*
-		 * Note: we don't worry about updating the page's prunability hints.
-		 * At worst this will cause an extra prune cycle to occur soon.
+		 * Update all line pointers per the record, and repair fragmentation
+		 * if needed.
 		 */
+		if (nredirected > 0 || ndead > 0 || nunused > 0)
+			heap_page_prune_execute(buffer,
+									(xlrec.flags & XLHP_CLEANUP_LOCK) == 0,
+									redirected, nredirected,
+									nowdead, ndead,
+									nowunused, nunused);
+
+		/* Freeze tuples */
+		for (int p = 0; p < nplans; p++)
+		{
+			HeapTupleFreeze frz;
 
-		PageSetLSN(page, lsn);
-		MarkBufferDirty(buffer);
-	}
+			/*
+			 * Convert freeze plan representation from WAL record into
+			 * per-tuple format used by heap_execute_freeze_tuple
+			 */
+			frz.xmax = plans[p].xmax;
+			frz.t_infomask2 = plans[p].t_infomask2;
+			frz.t_infomask = plans[p].t_infomask;
+			frz.frzflags = plans[p].frzflags;
+			frz.offset = InvalidOffsetNumber;	/* unused, but be tidy */
 
-	if (BufferIsValid(buffer))
-	{
-		Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
+			for (int i = 0; i < plans[p].ntuples; i++)
+			{
+				OffsetNumber offset = *(frz_offsets++);
+				ItemId		lp;
+				HeapTupleHeader tuple;
 
-		UnlockReleaseBuffer(buffer);
+				lp = PageGetItemId(page, offset);
+				tuple = (HeapTupleHeader) PageGetItem(page, lp);
+				heap_execute_freeze_tuple(tuple, &frz);
+			}
+		}
+
+		/* There should be no more data */
+		Assert((char *) frz_offsets == dataptr + datalen);
 
 		/*
-		 * After pruning records from a page, it's useful to update the FSM
-		 * about it, as it may cause the page become target for insertions
-		 * later even if vacuum decides not to visit it (which is possible if
-		 * gets marked all-visible.)
-		 *
-		 * Do this regardless of a full-page image being applied, since the
-		 * FSM data is not in the page anyway.
+		 * Note: we don't worry about updating the page's prunability hints.
+		 * At worst this will cause an extra prune cycle to occur soon.
 		 */
-		XLogRecordPageWithFreeSpace(rlocator, blkno, freespace);
-	}
-}
-
-/*
- * Handles XLOG_HEAP2_VACUUM record type.
- *
- * Acquires an ordinary exclusive lock only.
- */
-static void
-heap_xlog_vacuum(XLogReaderState *record)
-{
-	XLogRecPtr	lsn = record->EndRecPtr;
-	xl_heap_vacuum *xlrec = (xl_heap_vacuum *) XLogRecGetData(record);
-	Buffer		buffer;
-	BlockNumber blkno;
-	XLogRedoAction action;
-
-	/*
-	 * If we have a full-page image, restore it	(without using a cleanup lock)
-	 * and we're done.
-	 */
-	action = XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, false,
-										   &buffer);
-	if (action == BLK_NEEDS_REDO)
-	{
-		Page		page = (Page) BufferGetPage(buffer);
-		OffsetNumber *nowunused;
-		Size		datalen;
-		OffsetNumber *offnum;
-
-		nowunused = (OffsetNumber *) XLogRecGetBlockData(record, 0, &datalen);
-
-		/* Shouldn't be a record unless there's something to do */
-		Assert(xlrec->nunused > 0);
-
-		/* Update all now-unused line pointers */
-		offnum = nowunused;
-		for (int i = 0; i < xlrec->nunused; i++)
-		{
-			OffsetNumber off = *offnum++;
-			ItemId		lp = PageGetItemId(page, off);
-
-			Assert(ItemIdIsDead(lp) && !ItemIdHasStorage(lp));
-			ItemIdSetUnused(lp);
-		}
-
-		/* Attempt to truncate line pointer array now */
-		PageTruncateLinePointerArray(page);
 
 		PageSetLSN(page, lsn);
 		MarkBufferDirty(buffer);
 	}
 
+	/*
+	 * If we released any space or line pointers, update the free space map.
+	 *
+	 * Do this regardless of a full-page image being applied, since the FSM
+	 * data is not in the page anyway.
+	 */
 	if (BufferIsValid(buffer))
 	{
-		Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
-		RelFileLocator rlocator;
-
-		XLogRecGetBlockTag(record, 0, &rlocator, NULL, &blkno);
+		if (xlrec.flags & (XLHP_HAS_REDIRECTIONS |
+						   XLHP_HAS_DEAD_ITEMS |
+						   XLHP_HAS_NOW_UNUSED_ITEMS))
+		{
+			Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
 
-		UnlockReleaseBuffer(buffer);
+			UnlockReleaseBuffer(buffer);
 
-		/*
-		 * After vacuuming LP_DEAD items from a page, it's useful to update
-		 * the FSM about it, as it may cause the page become target for
-		 * insertions later even if vacuum decides not to visit it (which is
-		 * possible if gets marked all-visible.)
-		 *
-		 * Do this regardless of a full-page image being applied, since the
-		 * FSM data is not in the page anyway.
-		 */
-		XLogRecordPageWithFreeSpace(rlocator, blkno, freespace);
+			XLogRecordPageWithFreeSpace(rlocator, blkno, freespace);
+		}
+		else
+			UnlockReleaseBuffer(buffer);
 	}
 }
 
@@ -9050,74 +8873,6 @@ heap_xlog_visible(XLogReaderState *record)
 }
 
 /*
- * Replay XLOG_HEAP2_FREEZE_PAGE records
- */
-static void
-heap_xlog_freeze_page(XLogReaderState *record)
-{
-	XLogRecPtr	lsn = record->EndRecPtr;
-	xl_heap_freeze_page *xlrec = (xl_heap_freeze_page *) XLogRecGetData(record);
-	Buffer		buffer;
-
-	/*
-	 * In Hot Standby mode, ensure that there's no queries running which still
-	 * consider the frozen xids as running.
-	 */
-	if (InHotStandby)
-	{
-		RelFileLocator rlocator;
-
-		XLogRecGetBlockTag(record, 0, &rlocator, NULL, NULL);
-		ResolveRecoveryConflictWithSnapshot(xlrec->snapshotConflictHorizon,
-											xlrec->isCatalogRel,
-											rlocator);
-	}
-
-	if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)
-	{
-		Page		page = BufferGetPage(buffer);
-		xl_heap_freeze_plan *plans;
-		OffsetNumber *offsets;
-		int			curoff = 0;
-
-		plans = (xl_heap_freeze_plan *) XLogRecGetBlockData(record, 0, NULL);
-		offsets = (OffsetNumber *) ((char *) plans +
-									(xlrec->nplans *
-									 sizeof(xl_heap_freeze_plan)));
-		for (int p = 0; p < xlrec->nplans; p++)
-		{
-			HeapTupleFreeze frz;
-
-			/*
-			 * Convert freeze plan representation from WAL record into
-			 * per-tuple format used by heap_execute_freeze_tuple
-			 */
-			frz.xmax = plans[p].xmax;
-			frz.t_infomask2 = plans[p].t_infomask2;
-			frz.t_infomask = plans[p].t_infomask;
-			frz.frzflags = plans[p].frzflags;
-			frz.offset = InvalidOffsetNumber;	/* unused, but be tidy */
-
-			for (int i = 0; i < plans[p].ntuples; i++)
-			{
-				OffsetNumber offset = offsets[curoff++];
-				ItemId		lp;
-				HeapTupleHeader tuple;
-
-				lp = PageGetItemId(page, offset);
-				tuple = (HeapTupleHeader) PageGetItem(page, lp);
-				heap_execute_freeze_tuple(tuple, &frz);
-			}
-		}
-
-		PageSetLSN(page, lsn);
-		MarkBufferDirty(buffer);
-	}
-	if (BufferIsValid(buffer))
-		UnlockReleaseBuffer(buffer);
-}
-
-/*
  * Given an "infobits" field from an XLog record, set the correct bits in the
  * given infomask and infomask2 for the tuple touched by the record.
  *
@@ -10017,14 +9772,10 @@ heap2_redo(XLogReaderState *record)
 
 	switch (info & XLOG_HEAP_OPMASK)
 	{
-		case XLOG_HEAP2_PRUNE:
-			heap_xlog_prune(record);
-			break;
-		case XLOG_HEAP2_VACUUM:
-			heap_xlog_vacuum(record);
-			break;
-		case XLOG_HEAP2_FREEZE_PAGE:
-			heap_xlog_freeze_page(record);
+		case XLOG_HEAP2_PRUNE_ON_ACCESS:
+		case XLOG_HEAP2_PRUNE_VACUUM_SCAN:
+		case XLOG_HEAP2_PRUNE_VACUUM_CLEANUP:
+			heap_xlog_prune_freeze(record);
 			break;
 		case XLOG_HEAP2_VISIBLE:
 			heap_xlog_visible(record);