The patchset had a problem with all-zero pages, has appeared at index
build stage: the generic_log_relation() routine sends all pages into the
WAL. So  lsn field at all-zero page was initialized and the
PageIsVerified() routine detects it as a bad page.
The solution may be:
1. To improve index build algorithms and eliminate the possibility of
not used pages appearing.
2. To mark each page as 'dirty' right after initialization. In this case
we will got 'empty' page instead of the all-zeroed.
3. Do not write into the WAL all-zero pages.

In the patchset (see attachment) I used approach No.3.

On 04.02.2019 10:04, Michael Paquier wrote:
> On Tue, Dec 18, 2018 at 10:41:48AM +0500, Andrey Lepikhov wrote:
>> Ok. It is used only for demonstration.
> 
> The latest patch set needs a rebase, so moved to next CF, waiting on
> author as this got no reviews.
> --
> Michael
> 

-- 
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company
From ec20e8896181cf8b26755acaa6028a62a0c709e7 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov" <a.lepik...@postgrespro.ru>
Date: Wed, 6 Feb 2019 14:39:59 +0500
Subject: [PATCH 1/4] Relation-into-WAL-function

---
 src/backend/access/transam/generic_xlog.c | 48 +++++++++++++++++++++++
 src/include/access/generic_xlog.h         |  3 ++
 2 files changed, 51 insertions(+)

diff --git a/src/backend/access/transam/generic_xlog.c b/src/backend/access/transam/generic_xlog.c
index 5b00b7275b..c22e361747 100644
--- a/src/backend/access/transam/generic_xlog.c
+++ b/src/backend/access/transam/generic_xlog.c
@@ -542,3 +542,51 @@ generic_mask(char *page, BlockNumber blkno)
 
 	mask_unused_space(page);
 }
+
+/*
+ * Function to write generic xlog for every existing block of a relation.
+ * Caller is responsible for locking the relation exclusively.
+ */
+void
+generic_log_relation(Relation rel)
+{
+	BlockNumber 		blkno;
+	BlockNumber 		nblocks;
+	int					npbuf = 0;
+	GenericXLogState	*state = NULL;
+	Buffer				bufpack[MAX_GENERIC_XLOG_PAGES];
+
+	CHECK_FOR_INTERRUPTS();
+	nblocks = RelationGetNumberOfBlocks(rel);
+
+	/*
+	 * Iterate over all index pages and WAL-logging it. Pages are grouping into
+	 * the packages before adding to a WAL-record. Zero-pages are
+	 * not logged.
+	 */
+	for (blkno = 0; blkno < nblocks; blkno++)
+	{
+		Buffer	buf;
+
+		buf = ReadBuffer(rel, blkno);
+		if (!PageIsNew(BufferGetPage(buf)))
+		{
+			if (npbuf == 0)
+				state = GenericXLogStart(rel);
+
+			LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+			GenericXLogRegisterBuffer(state, buf, GENERIC_XLOG_FULL_IMAGE);
+			bufpack[npbuf++] = buf;
+		}
+		else
+			ReleaseBuffer(buf);
+
+		if ((npbuf == MAX_GENERIC_XLOG_PAGES) || (blkno == nblocks-1))
+		{
+			GenericXLogFinish(state);
+
+			for (; npbuf > 0; npbuf--)
+				UnlockReleaseBuffer(bufpack[npbuf-1]);
+		}
+	}
+}
diff --git a/src/include/access/generic_xlog.h b/src/include/access/generic_xlog.h
index cb5b5b713a..e3bbf014cc 100644
--- a/src/include/access/generic_xlog.h
+++ b/src/include/access/generic_xlog.h
@@ -42,4 +42,7 @@ extern const char *generic_identify(uint8 info);
 extern void generic_desc(StringInfo buf, XLogReaderState *record);
 extern void generic_mask(char *pagedata, BlockNumber blkno);
 
+/* other utils */
+extern void generic_log_relation(Relation rel);
+
 #endif							/* GENERIC_XLOG_H */
-- 
2.17.1

From 6fa828f6737d9c2dbcd2c2ce61a150e79e2bc1d2 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov" <a.lepik...@postgrespro.ru>
Date: Wed, 6 Feb 2019 14:40:29 +0500
Subject: [PATCH 2/4] GIN-Optimal-WAL-Usage

---
 src/backend/access/gin/ginbtree.c     |  6 ++---
 src/backend/access/gin/gindatapage.c  |  9 ++++----
 src/backend/access/gin/ginentrypage.c |  2 +-
 src/backend/access/gin/gininsert.c    | 30 ++++++++++--------------
 src/backend/access/gin/ginutil.c      |  4 ++--
 src/backend/access/gin/ginvacuum.c    |  2 +-
 src/backend/access/gin/ginxlog.c      | 33 ---------------------------
 src/backend/access/rmgrdesc/gindesc.c |  6 -----
 src/include/access/gin.h              |  3 ++-
 src/include/access/ginxlog.h          |  2 --
 10 files changed, 26 insertions(+), 71 deletions(-)

diff --git a/src/backend/access/gin/ginbtree.c b/src/backend/access/gin/ginbtree.c
index 533949e46a..9f82eef8c3 100644
--- a/src/backend/access/gin/ginbtree.c
+++ b/src/backend/access/gin/ginbtree.c
@@ -396,7 +396,7 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 		/* It will fit, perform the insertion */
 		START_CRIT_SECTION();
 
-		if (RelationNeedsWAL(btree->index))
+		if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 		{
 			XLogBeginInsert();
 			XLogRegisterBuffer(0, stack->buffer, REGBUF_STANDARD);
@@ -417,7 +417,7 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 			MarkBufferDirty(childbuf);
 		}
 
-		if (RelationNeedsWAL(btree->index))
+		if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 		{
 			XLogRecPtr	recptr;
 			ginxlogInsert xlrec;
@@ -595,7 +595,7 @@ ginPlaceToPage(GinBtree btree, GinBtreeStack *stack,
 		}
 
 		/* write WAL record */
-		if (RelationNeedsWAL(btree->index))
+		if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 		{
 			XLogRecPtr	recptr;
 
diff --git a/src/backend/access/gin/gindatapage.c b/src/backend/access/gin/gindatapage.c
index 3ad8b76710..f3aff62c8e 100644
--- a/src/backend/access/gin/gindatapage.c
+++ b/src/backend/access/gin/gindatapage.c
@@ -593,7 +593,7 @@ dataBeginPlaceToPageLeaf(GinBtree btree, Buffer buf, GinBtreeStack *stack,
 		 * Great, all the items fit on a single page.  If needed, prepare data
 		 * for a WAL record describing the changes we'll make.
 		 */
-		if (RelationNeedsWAL(btree->index))
+		if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 			computeLeafRecompressWALData(leaf);
 
 		/*
@@ -719,7 +719,7 @@ dataExecPlaceToPageLeaf(GinBtree btree, Buffer buf, GinBtreeStack *stack,
 	dataPlaceToPageLeafRecompress(buf, leaf);
 
 	/* If needed, register WAL data built by computeLeafRecompressWALData */
-	if (RelationNeedsWAL(btree->index))
+	if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 	{
 		XLogRegisterBufData(0, leaf->walinfo, leaf->walinfolen);
 	}
@@ -1152,7 +1152,7 @@ dataExecPlaceToPageInternal(GinBtree btree, Buffer buf, GinBtreeStack *stack,
 	pitem = (PostingItem *) insertdata;
 	GinDataPageAddPostingItem(page, pitem, off);
 
-	if (RelationNeedsWAL(btree->index))
+	if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 	{
 		/*
 		 * This must be static, because it has to survive until XLogInsert,
@@ -1773,6 +1773,7 @@ createPostingTree(Relation index, ItemPointerData *items, uint32 nitems,
 	Pointer		ptr;
 	int			nrootitems;
 	int			rootsize;
+	bool is_build = (buildStats != NULL);
 
 	/* Construct the new root page in memory first. */
 	tmppage = (Page) palloc(BLCKSZ);
@@ -1826,7 +1827,7 @@ createPostingTree(Relation index, ItemPointerData *items, uint32 nitems,
 	PageRestoreTempPage(tmppage, page);
 	MarkBufferDirty(buffer);
 
-	if (RelationNeedsWAL(index))
+	if (RelationNeedsWAL(index) && !is_build)
 	{
 		XLogRecPtr	recptr;
 		ginxlogCreatePostingTree data;
diff --git a/src/backend/access/gin/ginentrypage.c b/src/backend/access/gin/ginentrypage.c
index 4889de2a4f..1f5ba33d51 100644
--- a/src/backend/access/gin/ginentrypage.c
+++ b/src/backend/access/gin/ginentrypage.c
@@ -571,7 +571,7 @@ entryExecPlaceToPage(GinBtree btree, Buffer buf, GinBtreeStack *stack,
 		elog(ERROR, "failed to add item to index page in \"%s\"",
 			 RelationGetRelationName(btree->index));
 
-	if (RelationNeedsWAL(btree->index))
+	if (RelationNeedsWAL(btree->index) && !btree->isBuild)
 	{
 		/*
 		 * This must be static, because it has to survive until XLogInsert,
diff --git a/src/backend/access/gin/gininsert.c b/src/backend/access/gin/gininsert.c
index 524ac5be8b..6307743afd 100644
--- a/src/backend/access/gin/gininsert.c
+++ b/src/backend/access/gin/gininsert.c
@@ -17,6 +17,7 @@
 #include "access/gin_private.h"
 #include "access/ginxlog.h"
 #include "access/xloginsert.h"
+#include "access/generic_xlog.h"
 #include "catalog/index.h"
 #include "miscadmin.h"
 #include "storage/bufmgr.h"
@@ -194,6 +195,7 @@ ginEntryInsert(GinState *ginstate,
 		buildStats->nEntries++;
 
 	ginPrepareEntryScan(&btree, attnum, key, category, ginstate);
+	btree.isBuild = (buildStats != NULL);
 
 	stack = ginFindLeafPage(&btree, false, false, NULL);
 	page = BufferGetPage(stack->buffer);
@@ -346,23 +348,6 @@ ginbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	GinInitBuffer(RootBuffer, GIN_LEAF);
 	MarkBufferDirty(RootBuffer);
 
-	if (RelationNeedsWAL(index))
-	{
-		XLogRecPtr	recptr;
-		Page		page;
-
-		XLogBeginInsert();
-		XLogRegisterBuffer(0, MetaBuffer, REGBUF_WILL_INIT | REGBUF_STANDARD);
-		XLogRegisterBuffer(1, RootBuffer, REGBUF_WILL_INIT);
-
-		recptr = XLogInsert(RM_GIN_ID, XLOG_GIN_CREATE_INDEX);
-
-		page = BufferGetPage(RootBuffer);
-		PageSetLSN(page, recptr);
-
-		page = BufferGetPage(MetaBuffer);
-		PageSetLSN(page, recptr);
-	}
 
 	UnlockReleaseBuffer(MetaBuffer);
 	UnlockReleaseBuffer(RootBuffer);
@@ -417,7 +402,16 @@ ginbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	 * Update metapage stats
 	 */
 	buildstate.buildStats.nTotalPages = RelationGetNumberOfBlocks(index);
-	ginUpdateStats(index, &buildstate.buildStats);
+	ginUpdateStats(index, &buildstate.buildStats, true);
+
+	/*
+	 * Create generic wal records for all pages of relation, if necessary.
+	 * It seems reasonable not to generate WAL, if we recieved interrupt
+	 * signal.
+	 */
+	CHECK_FOR_INTERRUPTS();
+	if (RelationNeedsWAL(index))
+		generic_log_relation(index);
 
 	/*
 	 * Return statistics
diff --git a/src/backend/access/gin/ginutil.c b/src/backend/access/gin/ginutil.c
index afc20232ac..51b20bca6e 100644
--- a/src/backend/access/gin/ginutil.c
+++ b/src/backend/access/gin/ginutil.c
@@ -661,7 +661,7 @@ ginGetStats(Relation index, GinStatsData *stats)
  * Note: nPendingPages and ginVersion are *not* copied over
  */
 void
-ginUpdateStats(Relation index, const GinStatsData *stats)
+ginUpdateStats(Relation index, const GinStatsData *stats, bool is_build)
 {
 	Buffer		metabuffer;
 	Page		metapage;
@@ -691,7 +691,7 @@ ginUpdateStats(Relation index, const GinStatsData *stats)
 
 	MarkBufferDirty(metabuffer);
 
-	if (RelationNeedsWAL(index))
+	if (RelationNeedsWAL(index) && !is_build)
 	{
 		XLogRecPtr	recptr;
 		ginxlogUpdateMeta data;
diff --git a/src/backend/access/gin/ginvacuum.c b/src/backend/access/gin/ginvacuum.c
index dfe885b101..b9a28d1863 100644
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -759,7 +759,7 @@ ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
 
 	/* Update the metapage with accurate page and entry counts */
 	idxStat.nTotalPages = npages;
-	ginUpdateStats(info->index, &idxStat);
+	ginUpdateStats(info->index, &idxStat, false);
 
 	/* Finally, vacuum the FSM */
 	IndexFreeSpaceMapVacuum(info->index);
diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c
index c467ffa346..b648af1ff6 100644
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -40,36 +40,6 @@ ginRedoClearIncompleteSplit(XLogReaderState *record, uint8 block_id)
 		UnlockReleaseBuffer(buffer);
 }
 
-static void
-ginRedoCreateIndex(XLogReaderState *record)
-{
-	XLogRecPtr	lsn = record->EndRecPtr;
-	Buffer		RootBuffer,
-				MetaBuffer;
-	Page		page;
-
-	MetaBuffer = XLogInitBufferForRedo(record, 0);
-	Assert(BufferGetBlockNumber(MetaBuffer) == GIN_METAPAGE_BLKNO);
-	page = (Page) BufferGetPage(MetaBuffer);
-
-	GinInitMetabuffer(MetaBuffer);
-
-	PageSetLSN(page, lsn);
-	MarkBufferDirty(MetaBuffer);
-
-	RootBuffer = XLogInitBufferForRedo(record, 1);
-	Assert(BufferGetBlockNumber(RootBuffer) == GIN_ROOT_BLKNO);
-	page = (Page) BufferGetPage(RootBuffer);
-
-	GinInitBuffer(RootBuffer, GIN_LEAF);
-
-	PageSetLSN(page, lsn);
-	MarkBufferDirty(RootBuffer);
-
-	UnlockReleaseBuffer(RootBuffer);
-	UnlockReleaseBuffer(MetaBuffer);
-}
-
 static void
 ginRedoCreatePTree(XLogReaderState *record)
 {
@@ -767,9 +737,6 @@ gin_redo(XLogReaderState *record)
 	oldCtx = MemoryContextSwitchTo(opCtx);
 	switch (info)
 	{
-		case XLOG_GIN_CREATE_INDEX:
-			ginRedoCreateIndex(record);
-			break;
 		case XLOG_GIN_CREATE_PTREE:
 			ginRedoCreatePTree(record);
 			break;
diff --git a/src/backend/access/rmgrdesc/gindesc.c b/src/backend/access/rmgrdesc/gindesc.c
index ef30ce16b0..f3f4e1b214 100644
--- a/src/backend/access/rmgrdesc/gindesc.c
+++ b/src/backend/access/rmgrdesc/gindesc.c
@@ -78,9 +78,6 @@ gin_desc(StringInfo buf, XLogReaderState *record)
 
 	switch (info)
 	{
-		case XLOG_GIN_CREATE_INDEX:
-			/* no further information */
-			break;
 		case XLOG_GIN_CREATE_PTREE:
 			/* no further information */
 			break;
@@ -188,9 +185,6 @@ gin_identify(uint8 info)
 
 	switch (info & ~XLR_INFO_MASK)
 	{
-		case XLOG_GIN_CREATE_INDEX:
-			id = "CREATE_INDEX";
-			break;
 		case XLOG_GIN_CREATE_PTREE:
 			id = "CREATE_PTREE";
 			break;
diff --git a/src/include/access/gin.h b/src/include/access/gin.h
index 61fa697039..d559ffc703 100644
--- a/src/include/access/gin.h
+++ b/src/include/access/gin.h
@@ -71,6 +71,7 @@ extern int	gin_pending_list_limit;
 
 /* ginutil.c */
 extern void ginGetStats(Relation index, GinStatsData *stats);
-extern void ginUpdateStats(Relation index, const GinStatsData *stats);
+extern void ginUpdateStats(Relation index,
+						   const GinStatsData *stats, bool is_build);
 
 #endif							/* GIN_H */
diff --git a/src/include/access/ginxlog.h b/src/include/access/ginxlog.h
index 9bd4e0b9ba..2c5d743cac 100644
--- a/src/include/access/ginxlog.h
+++ b/src/include/access/ginxlog.h
@@ -16,8 +16,6 @@
 #include "lib/stringinfo.h"
 #include "storage/off.h"
 
-#define XLOG_GIN_CREATE_INDEX  0x00
-
 #define XLOG_GIN_CREATE_PTREE  0x10
 
 typedef struct ginxlogCreatePostingTree
-- 
2.17.1

From 679aa38c664eecba4a0d049feffe2537be3ebe21 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov" <a.lepik...@postgrespro.ru>
Date: Wed, 6 Feb 2019 14:41:08 +0500
Subject: [PATCH 3/4] GiST-Optimal-WAL-Usage

---
 src/backend/access/gist/gist.c         | 46 ++++++++++++++++++--------
 src/backend/access/gist/gistbuild.c    | 32 ++++++++++--------
 src/backend/access/gist/gistutil.c     |  2 +-
 src/backend/access/gist/gistxlog.c     | 22 ------------
 src/backend/access/rmgrdesc/gistdesc.c |  5 ---
 src/include/access/gist_private.h      |  7 ++--
 src/include/access/gistxlog.h          |  1 -
 7 files changed, 56 insertions(+), 59 deletions(-)

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index b75b3a8dac..c8f4e41db9 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -173,7 +173,7 @@ gistinsert(Relation r, Datum *values, bool *isnull,
 						 values, isnull, true /* size is currently bogus */ );
 	itup->t_tid = *ht_ctid;
 
-	gistdoinsert(r, itup, 0, giststate, heapRel);
+	gistdoinsert(r, itup, 0, giststate, heapRel, false);
 
 	/* cleanup */
 	MemoryContextSwitchTo(oldCxt);
@@ -220,7 +220,8 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 				Buffer leftchildbuf,
 				List **splitinfo,
 				bool markfollowright,
-				Relation heapRel)
+				Relation heapRel,
+				bool is_build)
 {
 	BlockNumber blkno = BufferGetBlockNumber(buffer);
 	Page		page = BufferGetPage(buffer);
@@ -459,7 +460,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		 * insertion for that. NB: The number of pages and data segments
 		 * specified here must match the calculations in gistXLogSplit()!
 		 */
-		if (RelationNeedsWAL(rel))
+		if (RelationNeedsWAL(rel) && !is_build)
 			XLogEnsureRecordSpace(npage, 1 + npage * 2);
 
 		START_CRIT_SECTION();
@@ -480,18 +481,20 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		PageRestoreTempPage(dist->page, BufferGetPage(dist->buffer));
 		dist->page = BufferGetPage(dist->buffer);
 
-		/* Write the WAL record */
-		if (RelationNeedsWAL(rel))
+		/*
+		 * Write the WAL record.
+		 * Do not write XLog entry if the insertion is caused by
+		 * index build process.
+		 */
+		if (RelationNeedsWAL(rel) && !is_build)
 			recptr = gistXLogSplit(is_leaf,
-								   dist, oldrlink, oldnsn, leftchildbuf,
-								   markfollowright);
+								dist, oldrlink, oldnsn, leftchildbuf,
+								markfollowright);
 		else
 			recptr = gistGetFakeLSN(rel);
 
 		for (ptr = dist; ptr; ptr = ptr->next)
-		{
 			PageSetLSN(ptr->page, recptr);
-		}
 
 		/*
 		 * Return the new child buffers to the caller.
@@ -545,7 +548,8 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		if (BufferIsValid(leftchildbuf))
 			MarkBufferDirty(leftchildbuf);
 
-		if (RelationNeedsWAL(rel))
+
+		if (RelationNeedsWAL(rel) && !is_build)
 		{
 			OffsetNumber ndeloffs = 0,
 						deloffs[1];
@@ -568,6 +572,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 			PageSetLSN(page, recptr);
 		}
 
+
 		if (newblkno)
 			*newblkno = blkno;
 	}
@@ -584,17 +589,28 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 	 * the full page image. There's a chicken-and-egg problem: if we updated
 	 * the child pages first, we wouldn't know the recptr of the WAL record
 	 * we're about to write.
+	 *
+	 * We use fakeLSNs for inserions caused by index build. And when it is
+	 * finished, we write generic_xlog entry for each index page and update
+	 * all LSNs. In order to keep NSNs less then LSNs after this update, we
+	 * set NSN to InvalidXLogRecPtr, which is the smallest possible NSN.
 	 */
+
 	if (BufferIsValid(leftchildbuf))
 	{
 		Page		leftpg = BufferGetPage(leftchildbuf);
+		XLogRecPtr	fakerecptr = InvalidXLogRecPtr;
 
-		GistPageSetNSN(leftpg, recptr);
-		GistClearFollowRight(leftpg);
+		if (!is_build)
+			GistPageSetNSN(leftpg, recptr);
+		else
+			GistPageSetNSN(leftpg, fakerecptr);
 
+		GistClearFollowRight(leftpg);
 		PageSetLSN(leftpg, recptr);
 	}
 
+
 	END_CRIT_SECTION();
 
 	return is_split;
@@ -607,7 +623,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
  */
 void
 gistdoinsert(Relation r, IndexTuple itup, Size freespace,
-			 GISTSTATE *giststate, Relation heapRel)
+			 GISTSTATE *giststate, Relation heapRel, bool is_build)
 {
 	ItemId		iid;
 	IndexTuple	idxtuple;
@@ -620,6 +636,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 	state.freespace = freespace;
 	state.r = r;
 	state.heapRel = heapRel;
+	state.is_build = is_build;
 
 	/* Start from the root */
 	firststack.blkno = GIST_ROOT_BLKNO;
@@ -1237,7 +1254,8 @@ gistinserttuples(GISTInsertState *state, GISTInsertStack *stack,
 							   leftchild,
 							   &splitinfo,
 							   true,
-							   state->heapRel);
+							   state->heapRel,
+							   state->is_build);
 
 	/*
 	 * Before recursing up in case the page was split, release locks on the
diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c
index bd142a3560..2e98e55187 100644
--- a/src/backend/access/gist/gistbuild.c
+++ b/src/backend/access/gist/gistbuild.c
@@ -17,6 +17,7 @@
 #include <math.h>
 
 #include "access/genam.h"
+#include "access/generic_xlog.h"
 #include "access/gist_private.h"
 #include "access/gistxlog.h"
 #include "access/xloginsert.h"
@@ -180,18 +181,12 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 
 	MarkBufferDirty(buffer);
 
-	if (RelationNeedsWAL(index))
-	{
-		XLogRecPtr	recptr;
-
-		XLogBeginInsert();
-		XLogRegisterBuffer(0, buffer, REGBUF_WILL_INIT);
-
-		recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_CREATE_INDEX);
-		PageSetLSN(page, recptr);
-	}
-	else
-		PageSetLSN(page, gistGetFakeLSN(heap));
+	/*
+	 * Do not write index pages to WAL unitl index build is finished.
+	 * But we still need increasing LSNs on each page, so use FakeLSN,
+	 * even for relations which eventually need WAL.
+	 */
+	PageSetLSN(page, gistGetFakeLSN(heap));
 
 	UnlockReleaseBuffer(buffer);
 
@@ -224,6 +219,15 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 
 	freeGISTstate(buildstate.giststate);
 
+	/*
+	 * Create generic wal records for all pages of relation, if necessary.
+	 * It seems reasonable not to generate WAL, if we recieved interrupt
+	 * signal.
+	 */
+	CHECK_FOR_INTERRUPTS();
+	if (RelationNeedsWAL(index))
+		generic_log_relation(index);
+
 	/*
 	 * Return statistics
 	 */
@@ -486,7 +490,7 @@ gistBuildCallback(Relation index,
 		 * locked, we call gistdoinsert directly.
 		 */
 		gistdoinsert(index, itup, buildstate->freespace,
-					 buildstate->giststate, buildstate->heaprel);
+					 buildstate->giststate, buildstate->heaprel, true);
 	}
 
 	/* Update tuple count and total size. */
@@ -693,7 +697,7 @@ gistbufferinginserttuples(GISTBuildState *buildstate, Buffer buffer, int level,
 							   InvalidBuffer,
 							   &splitinfo,
 							   false,
-							   buildstate->heaprel);
+							   buildstate->heaprel, true);
 
 	/*
 	 * If this is a root split, update the root path item kept in memory. This
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 8d3dfad27b..f7088e2d94 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -949,6 +949,7 @@ gistproperty(Oid index_oid, int attno,
  * Temporary and unlogged GiST indexes are not WAL-logged, but we need LSNs
  * to detect concurrent page splits anyway. This function provides a fake
  * sequence of LSNs for that purpose.
+ * Persistent relations are also not WAL-logged while we build index.
  */
 XLogRecPtr
 gistGetFakeLSN(Relation rel)
@@ -969,7 +970,6 @@ gistGetFakeLSN(Relation rel)
 		 * Unlogged relations are accessible from other backends, and survive
 		 * (clean) restarts. GetFakeLSNForUnloggedRel() handles that for us.
 		 */
-		Assert(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED);
 		return GetFakeLSNForUnloggedRel();
 	}
 }
diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
index 408bd5390a..66d5bb831f 100644
--- a/src/backend/access/gist/gistxlog.c
+++ b/src/backend/access/gist/gistxlog.c
@@ -489,25 +489,6 @@ gistRedoPageSplitRecord(XLogReaderState *record)
 	UnlockReleaseBuffer(firstbuffer);
 }
 
-static void
-gistRedoCreateIndex(XLogReaderState *record)
-{
-	XLogRecPtr	lsn = record->EndRecPtr;
-	Buffer		buffer;
-	Page		page;
-
-	buffer = XLogInitBufferForRedo(record, 0);
-	Assert(BufferGetBlockNumber(buffer) == GIST_ROOT_BLKNO);
-	page = (Page) BufferGetPage(buffer);
-
-	GISTInitBuffer(buffer, F_LEAF);
-
-	PageSetLSN(page, lsn);
-
-	MarkBufferDirty(buffer);
-	UnlockReleaseBuffer(buffer);
-}
-
 void
 gist_redo(XLogReaderState *record)
 {
@@ -532,9 +513,6 @@ gist_redo(XLogReaderState *record)
 		case XLOG_GIST_PAGE_SPLIT:
 			gistRedoPageSplitRecord(record);
 			break;
-		case XLOG_GIST_CREATE_INDEX:
-			gistRedoCreateIndex(record);
-			break;
 		default:
 			elog(PANIC, "gist_redo: unknown op code %u", info);
 	}
diff --git a/src/backend/access/rmgrdesc/gistdesc.c b/src/backend/access/rmgrdesc/gistdesc.c
index e468c9e15a..75f1ed747e 100644
--- a/src/backend/access/rmgrdesc/gistdesc.c
+++ b/src/backend/access/rmgrdesc/gistdesc.c
@@ -52,8 +52,6 @@ gist_desc(StringInfo buf, XLogReaderState *record)
 		case XLOG_GIST_PAGE_SPLIT:
 			out_gistxlogPageSplit(buf, (gistxlogPageSplit *) rec);
 			break;
-		case XLOG_GIST_CREATE_INDEX:
-			break;
 	}
 }
 
@@ -73,9 +71,6 @@ gist_identify(uint8 info)
 		case XLOG_GIST_PAGE_SPLIT:
 			id = "PAGE_SPLIT";
 			break;
-		case XLOG_GIST_CREATE_INDEX:
-			id = "CREATE_INDEX";
-			break;
 	}
 
 	return id;
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 3698942f9d..b1680bfd6d 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -242,6 +242,7 @@ typedef struct
 	Relation	r;
 	Relation	heapRel;
 	Size		freespace;		/* free space to be left */
+	bool		is_build;
 
 	GISTInsertStack *stack;
 } GISTInsertState;
@@ -391,7 +392,8 @@ extern void gistdoinsert(Relation r,
 			 IndexTuple itup,
 			 Size freespace,
 			 GISTSTATE *GISTstate,
-			 Relation heapRel);
+			 Relation heapRel,
+			 bool is_build);
 
 /* A List of these is returned from gistplacetopage() in *splitinfo */
 typedef struct
@@ -407,7 +409,8 @@ extern bool gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 				Buffer leftchildbuf,
 				List **splitinfo,
 				bool markleftchild,
-				Relation heapRel);
+				Relation heapRel,
+				bool is_build);
 
 extern SplitedPageLayout *gistSplit(Relation r, Page page, IndexTuple *itup,
 		  int len, GISTSTATE *giststate);
diff --git a/src/include/access/gistxlog.h b/src/include/access/gistxlog.h
index 5117aabf1a..2ee80e244e 100644
--- a/src/include/access/gistxlog.h
+++ b/src/include/access/gistxlog.h
@@ -22,7 +22,6 @@
  /* #define XLOG_GIST_NEW_ROOT			 0x20 */	/* not used anymore */
 #define XLOG_GIST_PAGE_SPLIT		0x30
  /* #define XLOG_GIST_INSERT_COMPLETE	 0x40 */	/* not used anymore */
-#define XLOG_GIST_CREATE_INDEX		0x50
  /* #define XLOG_GIST_PAGE_DELETE		 0x60 */	/* not used anymore */
 
 /*
-- 
2.17.1

From c89f89c963078dda856394cb1189d9d0580018f6 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov" <a.lepik...@postgrespro.ru>
Date: Wed, 6 Feb 2019 14:41:25 +0500
Subject: [PATCH 4/4] SP-GiST-Optimal-WAL-Usage

---
 src/backend/access/rmgrdesc/spgdesc.c   |  5 ----
 src/backend/access/spgist/spgdoinsert.c | 12 ++++-----
 src/backend/access/spgist/spginsert.c   | 24 +++--------------
 src/backend/access/spgist/spgxlog.c     | 35 -------------------------
 src/include/access/spgxlog.h            |  1 -
 5 files changed, 10 insertions(+), 67 deletions(-)

diff --git a/src/backend/access/rmgrdesc/spgdesc.c b/src/backend/access/rmgrdesc/spgdesc.c
index 37af31a764..40c1c8b3f9 100644
--- a/src/backend/access/rmgrdesc/spgdesc.c
+++ b/src/backend/access/rmgrdesc/spgdesc.c
@@ -24,8 +24,6 @@ spg_desc(StringInfo buf, XLogReaderState *record)
 
 	switch (info)
 	{
-		case XLOG_SPGIST_CREATE_INDEX:
-			break;
 		case XLOG_SPGIST_ADD_LEAF:
 			{
 				spgxlogAddLeaf *xlrec = (spgxlogAddLeaf *) rec;
@@ -88,9 +86,6 @@ spg_identify(uint8 info)
 
 	switch (info & ~XLR_INFO_MASK)
 	{
-		case XLOG_SPGIST_CREATE_INDEX:
-			id = "CREATE_INDEX";
-			break;
 		case XLOG_SPGIST_ADD_LEAF:
 			id = "ADD_LEAF";
 			break;
diff --git a/src/backend/access/spgist/spgdoinsert.c b/src/backend/access/spgist/spgdoinsert.c
index 0d07b8b291..c34c44cd8b 100644
--- a/src/backend/access/spgist/spgdoinsert.c
+++ b/src/backend/access/spgist/spgdoinsert.c
@@ -289,7 +289,7 @@ addLeafTuple(Relation index, SpGistState *state, SpGistLeafTuple leafTuple,
 
 	MarkBufferDirty(current->buffer);
 
-	if (RelationNeedsWAL(index))
+	if (RelationNeedsWAL(index) && !state->isBuild)
 	{
 		XLogRecPtr	recptr;
 		int			flags;
@@ -516,7 +516,7 @@ moveLeafs(Relation index, SpGistState *state,
 	MarkBufferDirty(current->buffer);
 	MarkBufferDirty(nbuf);
 
-	if (RelationNeedsWAL(index))
+	if (RelationNeedsWAL(index) && !state->isBuild)
 	{
 		XLogRecPtr	recptr;
 
@@ -1334,7 +1334,7 @@ doPickSplit(Relation index, SpGistState *state,
 		saveCurrent.buffer = InvalidBuffer;
 	}
 
-	if (RelationNeedsWAL(index))
+	if (RelationNeedsWAL(index) && !state->isBuild)
 	{
 		XLogRecPtr	recptr;
 		int			flags;
@@ -1531,7 +1531,7 @@ spgAddNodeAction(Relation index, SpGistState *state,
 
 		MarkBufferDirty(current->buffer);
 
-		if (RelationNeedsWAL(index))
+		if (RelationNeedsWAL(index) && !state->isBuild)
 		{
 			XLogRecPtr	recptr;
 
@@ -1644,7 +1644,7 @@ spgAddNodeAction(Relation index, SpGistState *state,
 
 		MarkBufferDirty(saveCurrent.buffer);
 
-		if (RelationNeedsWAL(index))
+		if (RelationNeedsWAL(index) && !state->isBuild)
 		{
 			XLogRecPtr	recptr;
 			int			flags;
@@ -1840,7 +1840,7 @@ spgSplitNodeAction(Relation index, SpGistState *state,
 
 	MarkBufferDirty(current->buffer);
 
-	if (RelationNeedsWAL(index))
+	if (RelationNeedsWAL(index) && !state->isBuild)
 	{
 		XLogRecPtr	recptr;
 
diff --git a/src/backend/access/spgist/spginsert.c b/src/backend/access/spgist/spginsert.c
index f428a15138..5da0183a9b 100644
--- a/src/backend/access/spgist/spginsert.c
+++ b/src/backend/access/spgist/spginsert.c
@@ -21,6 +21,7 @@
 #include "access/spgxlog.h"
 #include "access/xlog.h"
 #include "access/xloginsert.h"
+#include "access/generic_xlog.h"
 #include "catalog/index.h"
 #include "miscadmin.h"
 #include "storage/bufmgr.h"
@@ -104,26 +105,6 @@ spgbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	SpGistInitBuffer(nullbuffer, SPGIST_LEAF | SPGIST_NULLS);
 	MarkBufferDirty(nullbuffer);
 
-	if (RelationNeedsWAL(index))
-	{
-		XLogRecPtr	recptr;
-
-		XLogBeginInsert();
-
-		/*
-		 * Replay will re-initialize the pages, so don't take full pages
-		 * images.  No other data to log.
-		 */
-		XLogRegisterBuffer(0, metabuffer, REGBUF_WILL_INIT | REGBUF_STANDARD);
-		XLogRegisterBuffer(1, rootbuffer, REGBUF_WILL_INIT | REGBUF_STANDARD);
-		XLogRegisterBuffer(2, nullbuffer, REGBUF_WILL_INIT | REGBUF_STANDARD);
-
-		recptr = XLogInsert(RM_SPGIST_ID, XLOG_SPGIST_CREATE_INDEX);
-
-		PageSetLSN(BufferGetPage(metabuffer), recptr);
-		PageSetLSN(BufferGetPage(rootbuffer), recptr);
-		PageSetLSN(BufferGetPage(nullbuffer), recptr);
-	}
 
 	END_CRIT_SECTION();
 
@@ -150,6 +131,9 @@ spgbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 
 	SpGistUpdateMetaPage(index);
 
+	if (RelationNeedsWAL(index))
+		generic_log_relation(index);
+
 	result = (IndexBuildResult *) palloc0(sizeof(IndexBuildResult));
 	result->heap_tuples = reltuples;
 	result->index_tuples = buildstate.indtuples;
diff --git a/src/backend/access/spgist/spgxlog.c b/src/backend/access/spgist/spgxlog.c
index 71836ee8a5..ebe6ae8715 100644
--- a/src/backend/access/spgist/spgxlog.c
+++ b/src/backend/access/spgist/spgxlog.c
@@ -72,38 +72,6 @@ addOrReplaceTuple(Page page, Item tuple, int size, OffsetNumber offset)
 			 size);
 }
 
-static void
-spgRedoCreateIndex(XLogReaderState *record)
-{
-	XLogRecPtr	lsn = record->EndRecPtr;
-	Buffer		buffer;
-	Page		page;
-
-	buffer = XLogInitBufferForRedo(record, 0);
-	Assert(BufferGetBlockNumber(buffer) == SPGIST_METAPAGE_BLKNO);
-	page = (Page) BufferGetPage(buffer);
-	SpGistInitMetapage(page);
-	PageSetLSN(page, lsn);
-	MarkBufferDirty(buffer);
-	UnlockReleaseBuffer(buffer);
-
-	buffer = XLogInitBufferForRedo(record, 1);
-	Assert(BufferGetBlockNumber(buffer) == SPGIST_ROOT_BLKNO);
-	SpGistInitBuffer(buffer, SPGIST_LEAF);
-	page = (Page) BufferGetPage(buffer);
-	PageSetLSN(page, lsn);
-	MarkBufferDirty(buffer);
-	UnlockReleaseBuffer(buffer);
-
-	buffer = XLogInitBufferForRedo(record, 2);
-	Assert(BufferGetBlockNumber(buffer) == SPGIST_NULL_BLKNO);
-	SpGistInitBuffer(buffer, SPGIST_LEAF | SPGIST_NULLS);
-	page = (Page) BufferGetPage(buffer);
-	PageSetLSN(page, lsn);
-	MarkBufferDirty(buffer);
-	UnlockReleaseBuffer(buffer);
-}
-
 static void
 spgRedoAddLeaf(XLogReaderState *record)
 {
@@ -976,9 +944,6 @@ spg_redo(XLogReaderState *record)
 	oldCxt = MemoryContextSwitchTo(opCtx);
 	switch (info)
 	{
-		case XLOG_SPGIST_CREATE_INDEX:
-			spgRedoCreateIndex(record);
-			break;
 		case XLOG_SPGIST_ADD_LEAF:
 			spgRedoAddLeaf(record);
 			break;
diff --git a/src/include/access/spgxlog.h b/src/include/access/spgxlog.h
index 6527fc9eb1..8199b3f250 100644
--- a/src/include/access/spgxlog.h
+++ b/src/include/access/spgxlog.h
@@ -18,7 +18,6 @@
 #include "storage/off.h"
 
 /* XLOG record types for SPGiST */
-#define XLOG_SPGIST_CREATE_INDEX	0x00
 #define XLOG_SPGIST_ADD_LEAF		0x10
 #define XLOG_SPGIST_MOVE_LEAFS		0x20
 #define XLOG_SPGIST_ADD_NODE		0x30
-- 
2.17.1

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