From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 2 Nov 2021 19:02:49 +0000 (-0400)
Subject: Fix assorted bugs related to index pages.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=26e8dc432b6798cf51ec5cb2feb346dd58a6241e;p=users%2Frhaas%2Fpostgres.git

Fix assorted bugs related to index pages.

- cb_metapage_get_insert_state needs to return
  CBM_INSERT_NEEDS_INDEX_SEGMENT not only when the latest index
  segment is full but also when there are no index segments in
  existence yet.

- cb_metapage_remove_index_entries can't treat cbm_index_start
  == cbm_index_metapage_start as an error, or we'll never be able
  to move the first set of index entries out of the metapage.

- ConveyorBeltGetNewPage can allocate a new index segment without
  having a lock on prevbuffer if there are no index segments
  yet, since there is no such things as the previous index segment
  in that case.

- When we create a new index segment and then decide that our next
  action should be to relocate index entries into it, we must use
  the correct value for next_blkno.

- When adding the very first index segment, don't try to pin the
  first page of the previous index segment, since there isn't one.

- When adding a new index segment, use the free buffer we
  identified, rather than an uninitialized variable.

All per a test case from Dilip Kumar.
---

diff --git a/src/backend/access/conveyor/cbmetapage.c b/src/backend/access/conveyor/cbmetapage.c
index 68fdd412b6..d5f40af0e9 100644
--- a/src/backend/access/conveyor/cbmetapage.c
+++ b/src/backend/access/conveyor/cbmetapage.c
@@ -197,7 +197,8 @@ cb_metapage_get_insert_state(CBMetapageData *meta,
 			elog(ERROR,
 				 "newest index segment listed as using %u of %u entries",
 				 entries, maxentries);
-		else if (entries == maxentries)
+		else if (entries == maxentries ||
+				 meta->cbm_newest_index_segment == CB_INVALID_SEGMENT)
 			return CBM_INSERT_NEEDS_INDEX_SEGMENT;
 		else
 		{
@@ -374,8 +375,7 @@ cb_metapage_remove_index_entries(CBMetapageData *meta, unsigned count,
 		elog(ERROR, "removed index entries should be relocated if index segments exist");
 	if (relocating &&
 		(meta->cbm_oldest_index_segment == CB_INVALID_SEGMENT ||
-		 meta->cbm_newest_index_segment == CB_INVALID_SEGMENT ||
-		 meta->cbm_index_start == meta->cbm_index_metapage_start))
+		 meta->cbm_newest_index_segment == CB_INVALID_SEGMENT))
 		elog(ERROR, "removed index entries can't be relocated if no index segments exist");
 
 	/* Move any entries that we are keeping. */
diff --git a/src/backend/access/conveyor/conveyor.c b/src/backend/access/conveyor/conveyor.c
index 70935cfd9f..976a0292fd 100644
--- a/src/backend/access/conveyor/conveyor.c
+++ b/src/backend/access/conveyor/conveyor.c
@@ -350,7 +350,8 @@ ConveyorBeltGetNewPage(ConveyorBelt *cb, CBPageNo *pageno)
 		 */
 		if (can_allocate_segment &&
 			insert_state == CBM_INSERT_NEEDS_INDEX_SEGMENT &&
-			(!BufferIsValid(indexbuffer) || !BufferIsValid(prevbuffer)))
+			(!BufferIsValid(indexbuffer) || (!BufferIsValid(prevbuffer)
+			&& newest_index_segment != CB_INVALID_SEGMENT)))
 			can_allocate_segment = false;
 
 		/*
@@ -416,6 +417,7 @@ ConveyorBeltGetNewPage(ConveyorBelt *cb, CBPageNo *pageno)
 				 * index entries to that index segment.
 				 */
 				insert_state = CBM_INSERT_NEEDS_INDEX_ENTRIES_RELOCATED;
+				next_blkno = indexblock;
 			}
 
 			/*
@@ -533,15 +535,17 @@ ConveyorBeltGetNewPage(ConveyorBelt *cb, CBPageNo *pageno)
 		}
 
 		/*
-		 * If we need to add a new index segment, we'll have to update the
-		 * newest index page with a pointer to the index page we're going to
-		 * add, so we must read and pin that page.
+		 * If we need to add a new index segment and it's not the very first
+		 * one, we'll have to update the newest index page with a pointer to
+		 * the index page we're going to add, so we must read and pin that
+		 * page.
 		 *
 		 * The names "prevblock" and "prevbuffer" are intended to signify that
 		 * what is currently the newest index segment will become the previous
 		 * segment relative to the one we're going to add.
 		 */
-		if (insert_state == CBM_INSERT_NEEDS_INDEX_SEGMENT)
+		if (insert_state == CBM_INSERT_NEEDS_INDEX_SEGMENT &&
+			newest_index_segment != CB_INVALID_SEGMENT)
 		{
 			prevblock = cb_segment_to_block(cb->cb_pages_per_segment,
 											newest_index_segment, 0);
@@ -593,7 +597,7 @@ ConveyorBeltGetNewPage(ConveyorBelt *cb, CBPageNo *pageno)
 				if (insert_state == CBM_INSERT_NEEDS_INDEX_SEGMENT)
 				{
 					indexblock = free_block;
-					indexbuffer = buffer;
+					indexbuffer = free_buffer;
 				}
 				else
 					ReleaseBuffer(free_buffer);