Re: Failure in contrib test _int on loach
On 08/05/2019 01:31, Heikki Linnakangas wrote: On 02/05/2019 10:37, Heikki Linnakangas wrote: On 29/04/2019 16:16, Anastasia Lubennikova wrote: In previous emails, I have sent two patches with test and bugfix (see attached). After Heikki shared his concerns, I've rechecked the algorithm and haven't found any potential error. So, if other hackers are agreed with my reasoning, the suggested fix is sufficient and can be committed. I still believe there is a problem with grandparent splits with this. I'll try to construct a test case later this week, unless you manage to create one before that. Here you go. If you apply the two patches from https://www.postgresql.org/message-id/5d48ce28-34cf-9b03-5d42-dbd5457926bf%40postgrespro.ru, and run the attached script, it will print out something like this: postgres=# \i grandparent.sql DROP TABLE CREATE TABLE INSERT 0 15 CREATE INDEX psql:grandparent.sql:27: NOTICE: working on 1 psql:grandparent.sql:27: NOTICE: working on 2 psql:grandparent.sql:27: NOTICE: working on 3 psql:grandparent.sql:27: NOTICE: working on 4 psql:grandparent.sql:27: NOTICE: working on 5 psql:grandparent.sql:27: NOTICE: working on 6 psql:grandparent.sql:27: NOTICE: working on 7 psql:grandparent.sql:27: NOTICE: working on 8 psql:grandparent.sql:27: NOTICE: working on 9 psql:grandparent.sql:27: NOTICE: working on 10 psql:grandparent.sql:27: NOTICE: working on 11 psql:grandparent.sql:27: NOTICE: failed for 114034 psql:grandparent.sql:27: NOTICE: working on 12 DO That "failed for 114034" should not happen. Fortunately, that's not too hard to fix. We just need to arrange things so that the "retry_from_parent" flag also gets set for the grandparent, when the grandparent is split. Like in the attached patch. I hear no objections, so pushed that. But if you have a chance to review this later, just to double-check, I'd still appreciate that. - Heikki
Re: Failure in contrib test _int on loach
(resending, previous attempt didn't make it to pgsql-hackers) On 29/04/2019 16:16, Anastasia Lubennikova wrote: In previous emails, I have sent two patches with test and bugfix (see attached). After Heikki shared his concerns, I've rechecked the algorithm and haven't found any potential error. So, if other hackers are agreed with my reasoning, the suggested fix is sufficient and can be committed. I still believe there is a problem with grandparent splits with this. I'll try to construct a test case later this week, unless you manage to create one before that. - Heikki
Re: Failure in contrib test _int on loach
Hi!
So, if other hackers are agreed with my reasoning, the suggested fix is
sufficient and can be committed.
Patch looks right, but I think that comment should be improved in follow piece:
if (stack->blkno != GIST_ROOT_BLKNO &&
- stack->parent->lsn < GistPageGetNSN(stack->page))
+ ((stack->parent->lsn < GistPageGetNSN(stack->page)) ||
+stack->retry_from_parent == true))
{
/*
* Concurrent split detected. There's no guarantee that the
Not only concurrent split could be deteced here and it was missed long ago. But
this patch seems a good chance to change this comment.
--
Teodor Sigaev E-mail: teo...@sigaev.ru
WWW: http://www.sigaev.ru/
Re: Failure in contrib test _int on loach
27.04.2019 22:05, Tom Lane wrote:
Anastasia Lubennikova writes:
So it is possible, but it doesn't require any extra algorithm changes.
I didn't manage to generate dataset to reproduce grandparent split.
Though, I do agree that it's worth checking out. Do you have any ideas?
Ping? This thread has gone cold, but the bug is still there, and
IMV it's a beta blocker.
Hi,
Thank you for the reminder.
In a nutshell, this fix is ready for committer.
In previous emails, I have sent two patches with test and bugfix (see
attached).
After Heikki shared his concerns, I've rechecked the algorithm and
haven't found any potential error.
So, if other hackers are agreed with my reasoning, the suggested fix is
sufficient and can be committed.
--
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
commit 53938b423ec19a88e470b7b9552de13de5e2634a
Author: Anastasia
Date: Tue Apr 9 18:58:00 2019 +0300
fix for gist create index WAL optimization. Track splits correctly
diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 2db790c..ff98d13 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -639,6 +639,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
/* Start from the root */
firststack.blkno = GIST_ROOT_BLKNO;
firststack.lsn = 0;
+ firststack.retry_from_parent = false;
firststack.parent = NULL;
firststack.downlinkoffnum = InvalidOffsetNumber;
state.stack = stack =
@@ -693,8 +694,15 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
continue;
}
+ /*
+ * During gistbuild we cannot rely on lsn-nsn comparison,
+ * since all pages have the same GistBuildLSN value in these fields.
+ * So use special flag stack->retry_from_parent to detect the fact that
+ * we need to go back to parent and rechoose the child.
+ */
if (stack->blkno != GIST_ROOT_BLKNO &&
- stack->parent->lsn < GistPageGetNSN(stack->page))
+ ((stack->parent->lsn < GistPageGetNSN(stack->page)) ||
+ stack->retry_from_parent == true))
{
/*
* Concurrent split detected. There's no guarantee that the
@@ -786,6 +794,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
+ stack->retry_from_parent = true;
}
continue;
}
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 78e2e3f..361a7a8 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -215,6 +215,12 @@ typedef struct GISTInsertStack
*/
GistNSN lsn;
+ /*
+ * flag to use during gistbuild to recognize page split
+ * (instead of lsn-nsn comparison)
+ */
+ bool retry_from_parent;
+
/* offset of the downlink in the parent page, that points to this page */
OffsetNumber downlinkoffnum;
commit 53f4607b50e0516be05ef27d9369c89bdcb9d82b
Author: Anastasia
Date: Tue Apr 9 18:56:32 2019 +0300
test
diff --git a/contrib/intarray/Makefile b/contrib/intarray/Makefile
index 2505294..3535bb1 100644
--- a/contrib/intarray/Makefile
+++ b/contrib/intarray/Makefile
@@ -9,7 +9,7 @@ DATA = intarray--1.2.sql intarray--1.1--1.2.sql intarray--1.0--1.1.sql \
intarray--unpackaged--1.0.sql
PGFILEDESC = "intarray - functions and operators for arrays of integers"
-REGRESS = _int
+REGRESS = _int _int2
ifdef USE_PGXS
PG_CONFIG = pg_config
diff --git a/contrib/intarray/expected/_int2.out b/contrib/intarray/expected/_int2.out
new file mode 100644
index 000..8346334
--- /dev/null
+++ b/contrib/intarray/expected/_int2.out
@@ -0,0 +1,47 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count
+---
+ 403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count
+---
+ 403
+(1 row)
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count
+---
+ 403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count
+---
+ 403
+(1 row)
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+ a | t
+---+---
+(0 rows)
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+ a
+---
+ {193,213,230,266,285,299}
+(1 row)
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+ a
+---
+ {193,213,230,266,285,299}
+(1 row)
+
diff --git a/contrib/intarray/sql/_int2.sql b/contrib/intarray/sql/_int2.sql
new file mode 100644
index 000..d4adca7
--- /dev/null
+++ b/contrib/intarray/sql/_int2.sql
@@ -0,0 +1,20 @@
+CREATE
Re: Failure in contrib test _int on loach
Anastasia Lubennikova writes: > So it is possible, but it doesn't require any extra algorithm changes. > I didn't manage to generate dataset to reproduce grandparent split. > Though, I do agree that it's worth checking out. Do you have any ideas? Ping? This thread has gone cold, but the bug is still there, and IMV it's a beta blocker. regards, tom lane
Re: Failure in contrib test _int on loach
10.04.2019 18:25, Heikki Linnakangas writes: On 09/04/2019 19:11, Anastasia Lubennikova wrote: 05.04.2019 19:41, Anastasia Lubennikova writes: In attachment, you can find patch with a test that allows to reproduce the bug not randomly, but on every run. Now I'm trying to find a way to fix the issue. The problem was caused by incorrect detection of the page to insert new tuple after split. If gistinserttuple() of the tuple formed by gistgetadjusted() had to split the page, we must to go back to the parent and descend back to the child that's a better fit for the new tuple. Previously this was handled by the code block with the following comment: * Concurrent split detected. There's no guarantee that the * downlink for this page is consistent with the tuple we're * inserting anymore, so go back to parent and rechoose the best * child. After introducing GistBuildNSN this code path became unreachable. To fix it, I added new flag to detect such splits during indexbuild. Isn't it possible that the grandparent page is also split, so that we'd need to climb further up? From what I understand, the only reason for grandparent's split during gistbuild is the insertion of the newtup returned by gistgetadjusted(). After we stepped up the stack, we will do gistchoose() to choose new correct child, adjust the downlink key and insert it into grandparent. If this insertion caused split, we will recursively follow the same codepath and set stack->retry_from_parent again. So it is possible, but it doesn't require any extra algorithm changes. I didn't manage to generate dataset to reproduce grandparent split. Though, I do agree that it's worth checking out. Do you have any ideas? -- Anastasia Lubennikova Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
Re: Failure in contrib test _int on loach
On 11/04/2019 13:14, Heikki Linnakangas wrote: On 11/04/2019 09:10, Andrey Lepikhov wrote: On 10/04/2019 20:25, Heikki Linnakangas wrote: On 09/04/2019 19:11, Anastasia Lubennikova wrote: After introducing GistBuildNSN this code path became unreachable. To fix it, I added new flag to detect such splits during indexbuild. Isn't it possible that the grandparent page is also split, so that we'd need to climb further up? Based on Anastasia's idea i prepare alternative solution to fix the bug (see attachment). It utilizes the idea of linear increment of LSN/NSN. WAL write process is used for change NSN value to 1 for each block of index relation. I hope this can be a fairly clear and safe solution. That's basically the same idea as always using the "fake LSN" during index build, like the original version of this patch did. It's got the problem that I mentioned at https://www.postgresql.org/message-id/090fb3cb-1ca4-e173-ecf7-47d41ebac...@iki.fi: * Using "fake" unlogged LSNs for GiST index build seemed fishy. I could not convince myself that it was safe in all corner cases. In a recently initdb'd cluster, it's theoretically possible that the fake LSN counter overtakes the real LSN value, and that could lead to strange behavior. For example, how would the buffer manager behave, if there was a dirty page in the buffer cache with an LSN value that's greater than the current WAL flush pointer? I think you'd get "ERROR: xlog flush request %X/%X is not satisfied --- flushed only to %X/%X". Perhaps the risk is theoretical; the real WAL begins at XLOG_SEG_SIZE, so with defaults WAL segment size, the index build would have to do about 16 million page splits. The index would have to be at least 150 GB for that. But it seems possible, and with non-default segment and page size settings more so. As i see in bufmgr.c, XLogFlush() can't called during index build. In the log_newpage_range() call we can use mask to set value of NSN (and LSN) to 1. Perhaps we could start at 1, but instead of using a global counter, whenever a page is split, we take the parent's LSN value and increment it by one. So different branches of the tree could use the same values, which would reduce the consumption of the counter values. Yet another idea would be to start the counter at 1, but check that it doesn't overtake the WAL insert pointer. If it's about to overtake it, just generate some dummy WAL. But it seems best to deal with this in gistdoinsert(). I think Anastasia's approach of adding a flag to GISTInsertStack can be made to work, if we set the flag somewhere in gistinserttuples() or gistplacetopage(), whenever a page is split. That way, if it needs to split multiple levels, the flag is set on all of the corresponding GISTInsertStack entries. Yet another trivial fix would be just always start the tree descend from the root in gistdoinsert(), if a page is split. Not as efficient, but probably negligible in practice. Agree -- Andrey Lepikhov Postgres Professional https://postgrespro.com The Russian Postgres Company
Re: Failure in contrib test _int on loach
On 10/04/2019 20:25, Heikki Linnakangas wrote:
On 09/04/2019 19:11, Anastasia Lubennikova wrote:
05.04.2019 19:41, Anastasia Lubennikova writes:
In attachment, you can find patch with a test that allows to reproduce
the bug not randomly, but on every run.
Now I'm trying to find a way to fix the issue.
The problem was caused by incorrect detection of the page to insert new
tuple after split.
If gistinserttuple() of the tuple formed by gistgetadjusted() had to
split the page, we must to go back to the parent and
descend back to the child that's a better fit for the new tuple.
Previously this was handled by the code block with the following comment:
* Concurrent split detected. There's no guarantee that the
* downlink for this page is consistent with the tuple we're
* inserting anymore, so go back to parent and rechoose the best
* child.
After introducing GistBuildNSN this code path became unreachable.
To fix it, I added new flag to detect such splits during indexbuild.
Isn't it possible that the grandparent page is also split, so that we'd
need to climb further up?
Based on Anastasia's idea i prepare alternative solution to fix the bug
(see attachment).
It utilizes the idea of linear increment of LSN/NSN. WAL write process
is used for change NSN value to 1 for each block of index relation.
I hope this can be a fairly clear and safe solution.
--
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company
>From 59e1519a0a48b879777820ff68116c68ed31e684 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov"
Date: Thu, 11 Apr 2019 10:52:39 +0500
Subject: [PATCH] Alt fix for gist_optimized_wal_intarray_test bug
---
src/backend/access/gin/gininsert.c | 2 +-
src/backend/access/gist/gist.c | 4 ++--
src/backend/access/gist/gistbuild.c | 17 +++--
src/backend/access/spgist/spginsert.c | 2 +-
src/backend/access/transam/xloginsert.c | 4 +++-
src/include/access/gist.h | 6 --
src/include/access/gist_private.h | 2 ++
src/include/access/xloginsert.h | 6 +-
8 files changed, 29 insertions(+), 14 deletions(-)
diff --git a/src/backend/access/gin/gininsert.c b/src/backend/access/gin/gininsert.c
index 55eab14617..a63f33b429 100644
--- a/src/backend/access/gin/gininsert.c
+++ b/src/backend/access/gin/gininsert.c
@@ -413,7 +413,7 @@ ginbuild(Relation heap, Relation index, IndexInfo *indexInfo)
{
log_newpage_range(index, MAIN_FORKNUM,
0, RelationGetNumberOfBlocks(index),
- true);
+ true, NULL);
}
/*
diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 2db790c840..56f6ce04db 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -492,7 +492,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
* we don't need to be able to detect concurrent splits yet.)
*/
if (is_build)
- recptr = GistBuildLSN;
+ recptr = gistBuildLSN++;
else
{
if (RelationNeedsWAL(rel))
@@ -559,7 +559,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
MarkBufferDirty(leftchildbuf);
if (is_build)
- recptr = GistBuildLSN;
+ recptr = gistBuildLSN++;
else
{
if (RelationNeedsWAL(rel))
diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c
index 8e81eda517..31118b54cf 100644
--- a/src/backend/access/gist/gistbuild.c
+++ b/src/backend/access/gist/gistbuild.c
@@ -76,6 +76,13 @@ typedef struct
GistBufferingMode bufferingMode;
} GISTBuildState;
+/*
+ * A bogus LSN / NSN value used during index build. Must be smaller than any
+ * real or fake unlogged LSN, so that after an index build finishes, all the
+ * splits are considered completed.
+ */
+XLogRecPtr gistBuildLSN = 0;
+
/* prototypes for private functions */
static void gistInitBuffering(GISTBuildState *buildstate);
static int calculatePagesPerBuffer(GISTBuildState *buildstate, int levelStep);
@@ -107,6 +114,12 @@ static void gistMemorizeParent(GISTBuildState *buildstate, BlockNumber child,
static void gistMemorizeAllDownlinks(GISTBuildState *buildstate, Buffer parent);
static BlockNumber gistGetParent(GISTBuildState *buildstate, BlockNumber child);
+static void
+gistbuild_log_mask(char *page)
+{
+ GistPageSetNSN((Page) page, (uint64) 1);
+}
+
/*
* Main entry point to GiST index build. Initially calls insert over and over,
* but switches to more efficient buffering build algorithm after a certain
@@ -180,7 +193,7 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
GISTInitBuffer(buffer, F_LEAF);
MarkBufferDirty(buffer);
- PageSetLSN(page, GistBuildLSN);
+ PageSetLSN(page, gistBuildLSN++);
UnlockReleaseBuffer(buffer);
@@ -222,7 +235,7 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
{
log_newpage_range(index, MAIN_FORKNUM,
0, RelationGetNumberOfBlocks(index),
- true);
+ true, gistbuild_log_mask);
Re: Failure in contrib test _int on loach
On 09/04/2019 19:11, Anastasia Lubennikova wrote: 05.04.2019 19:41, Anastasia Lubennikova writes: In attachment, you can find patch with a test that allows to reproduce the bug not randomly, but on every run. Now I'm trying to find a way to fix the issue. The problem was caused by incorrect detection of the page to insert new tuple after split. If gistinserttuple() of the tuple formed by gistgetadjusted() had to split the page, we must to go back to the parent and descend back to the child that's a better fit for the new tuple. Previously this was handled by the code block with the following comment: * Concurrent split detected. There's no guarantee that the * downlink for this page is consistent with the tuple we're * inserting anymore, so go back to parent and rechoose the best * child. After introducing GistBuildNSN this code path became unreachable. To fix it, I added new flag to detect such splits during indexbuild. Isn't it possible that the grandparent page is also split, so that we'd need to climb further up? - Heikki
Re: Failure in contrib test _int on loach
05.04.2019 19:41, Anastasia Lubennikova writes:
05.04.2019 18:01, Tom Lane writes:
Andrew Dunstan writes:
On Fri, Apr 5, 2019 at 2:02 AM Thomas Munro
wrote:
This is a strange failure:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach=2019-04-05%2005%3A15%3A00
[ wrong answers from queries using a GIST index ]
There are a couple of other recent instances of this failure, on
francolin and whelk.
Yeah. Given three failures in a couple of days, we can reasonably
guess that the problem was introduced within a day or two prior to
the first one. Looking at what's touched GIST in that time frame,
suspicion has to fall heavily on
9155580fd5fc2a0cbb23376dfca7cd21f59c2c7b.
If I had to bet, I'd bet that there's something wrong with the
machinations described in the commit message:
For GiST, the LSN-NSN interlock makes this a little tricky.
All pages must
be marked with a valid (i.e. non-zero) LSN, so that the
parent-child
LSN-NSN interlock works correctly. We now use magic value 1 for
that during
index build. Change the fake LSN counter to begin from 1000, so
that 1 is
safely smaller than any real or fake LSN. 2 would've been enough
for our
purposes, but let's reserve a bigger range, in case we need more
special
values in the future.
I'll go add this as an open issue.
regards, tom lane
Hi,
I've already noticed the same failure in our company buildfarm and
started the research.
You are right, it's the " Generate less WAL during GiST, GIN and
SP-GiST index build. " patch to blame.
Because of using the GistBuildLSN some pages are not linked correctly,
so index scan cannot find some entries, while seqscan finds them.
In attachment, you can find patch with a test that allows to reproduce
the bug not randomly, but on every run.
Now I'm trying to find a way to fix the issue.
The problem was caused by incorrect detection of the page to insert new
tuple after split.
If gistinserttuple() of the tuple formed by gistgetadjusted() had to
split the page, we must to go back to the parent and
descend back to the child that's a better fit for the new tuple.
Previously this was handled by the code block with the following comment:
* Concurrent split detected. There's no guarantee that the
* downlink for this page is consistent with the tuple we're
* inserting anymore, so go back to parent and rechoose the best
* child.
After introducing GistBuildNSN this code path became unreachable.
To fix it, I added new flag to detect such splits during indexbuild.
The patches with the test and fix are attached.
Many thanks to Teodor Sigaev, who helped to find the bug.
--
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
commit 53938b423ec19a88e470b7b9552de13de5e2634a
Author: Anastasia
Date: Tue Apr 9 18:58:00 2019 +0300
fix for gist create index WAL optimization. Track splits correctly
diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 2db790c..ff98d13 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -639,6 +639,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
/* Start from the root */
firststack.blkno = GIST_ROOT_BLKNO;
firststack.lsn = 0;
+ firststack.retry_from_parent = false;
firststack.parent = NULL;
firststack.downlinkoffnum = InvalidOffsetNumber;
state.stack = stack =
@@ -693,8 +694,15 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
continue;
}
+ /*
+ * During gistbuild we cannot rely on lsn-nsn comparison,
+ * since all pages have the same GistBuildLSN value in these fields.
+ * So use special flag stack->retry_from_parent to detect the fact that
+ * we need to go back to parent and rechoose the child.
+ */
if (stack->blkno != GIST_ROOT_BLKNO &&
- stack->parent->lsn < GistPageGetNSN(stack->page))
+ ((stack->parent->lsn < GistPageGetNSN(stack->page)) ||
+ stack->retry_from_parent == true))
{
/*
* Concurrent split detected. There's no guarantee that the
@@ -786,6 +794,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
+ stack->retry_from_parent = true;
}
continue;
}
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 78e2e3f..361a7a8 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -215,6 +215,12 @@ typedef struct GISTInsertStack
*/
GistNSN lsn;
+ /*
+ * flag to use during gistbuild to recognize page split
+ * (instead of lsn-nsn comparison)
+ */
+ bool retry_from_parent;
+
/* offset of the downlink in the parent page, that points to this page */
OffsetNumber downlinkoffnum;
commit 53f4607b50e0516be05ef27d9369c89bdcb9d82b
Author: Anastasia
Date: Tue Apr 9 18:56:32 2019 +0300
test
Re: Failure in contrib test _int on loach
05.04.2019 18:01, Tom Lane writes:
Andrew Dunstan writes:
On Fri, Apr 5, 2019 at 2:02 AM Thomas Munro wrote:
This is a strange failure:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach=2019-04-05%2005%3A15%3A00
[ wrong answers from queries using a GIST index ]
There are a couple of other recent instances of this failure, on
francolin and whelk.
Yeah. Given three failures in a couple of days, we can reasonably
guess that the problem was introduced within a day or two prior to
the first one. Looking at what's touched GIST in that time frame,
suspicion has to fall heavily on 9155580fd5fc2a0cbb23376dfca7cd21f59c2c7b.
If I had to bet, I'd bet that there's something wrong with the
machinations described in the commit message:
For GiST, the LSN-NSN interlock makes this a little tricky. All pages must
be marked with a valid (i.e. non-zero) LSN, so that the parent-child
LSN-NSN interlock works correctly. We now use magic value 1 for that during
index build. Change the fake LSN counter to begin from 1000, so that 1 is
safely smaller than any real or fake LSN. 2 would've been enough for our
purposes, but let's reserve a bigger range, in case we need more special
values in the future.
I'll go add this as an open issue.
regards, tom lane
Hi,
I've already noticed the same failure in our company buildfarm and
started the research.
You are right, it's the " Generate less WAL during GiST, GIN and SP-GiST
index build. " patch to blame.
Because of using the GistBuildLSN some pages are not linked correctly,
so index scan cannot find some entries, while seqscan finds them.
In attachment, you can find patch with a test that allows to reproduce
the bug not randomly, but on every run.
Now I'm trying to find a way to fix the issue.
--
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
commit b233d40c1bd1b270ec0ea1d52887794320a8f595
Author: Anastasia
Date: Fri Apr 5 19:25:48 2019 +0300
Test to reproduce gist index problem caused by patch Generate less WAL during GiST, GIN and SP-GiST index build
diff --git a/contrib/intarray/Makefile b/contrib/intarray/Makefile
index 2505294..3535bb1 100644
--- a/contrib/intarray/Makefile
+++ b/contrib/intarray/Makefile
@@ -9,7 +9,7 @@ DATA = intarray--1.2.sql intarray--1.1--1.2.sql intarray--1.0--1.1.sql \
intarray--unpackaged--1.0.sql
PGFILEDESC = "intarray - functions and operators for arrays of integers"
-REGRESS = _int
+REGRESS = _int _int2
ifdef USE_PGXS
PG_CONFIG = pg_config
diff --git a/contrib/intarray/expected/_int2.out b/contrib/intarray/expected/_int2.out
new file mode 100644
index 000..e88fd34
--- /dev/null
+++ b/contrib/intarray/expected/_int2.out
@@ -0,0 +1,48 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count
+---
+ 403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count
+---
+ 403
+(1 row)
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count
+---
+ 403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count
+---
+ 403
+(1 row)
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+ a | t
+---+---
+(0 rows)
+
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+ a
+---
+ {193,213,230,266,285,299}
+(1 row)
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+ a
+---
+ {193,213,230,266,285,299}
+(1 row)
+
diff --git a/contrib/intarray/sql/_int2.sql b/contrib/intarray/sql/_int2.sql
new file mode 100644
index 000..d4adca7
--- /dev/null
+++ b/contrib/intarray/sql/_int2.sql
@@ -0,0 +1,20 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 94b6ad6..2183b3a 100644
---
Re: Failure in contrib test _int on loach
Andrew Dunstan writes: > On Fri, Apr 5, 2019 at 2:02 AM Thomas Munro wrote: >> This is a strange failure: >> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach=2019-04-05%2005%3A15%3A00 >> [ wrong answers from queries using a GIST index ] > There are a couple of other recent instances of this failure, on > francolin and whelk. Yeah. Given three failures in a couple of days, we can reasonably guess that the problem was introduced within a day or two prior to the first one. Looking at what's touched GIST in that time frame, suspicion has to fall heavily on 9155580fd5fc2a0cbb23376dfca7cd21f59c2c7b. If I had to bet, I'd bet that there's something wrong with the machinations described in the commit message: For GiST, the LSN-NSN interlock makes this a little tricky. All pages must be marked with a valid (i.e. non-zero) LSN, so that the parent-child LSN-NSN interlock works correctly. We now use magic value 1 for that during index build. Change the fake LSN counter to begin from 1000, so that 1 is safely smaller than any real or fake LSN. 2 would've been enough for our purposes, but let's reserve a bigger range, in case we need more special values in the future. I'll go add this as an open issue. regards, tom lane
Re: Failure in contrib test _int on loach
On Fri, Apr 5, 2019 at 2:02 AM Thomas Munro wrote:
>
> Hi,
>
> This is a strange failure:
>
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach=2019-04-05%2005%3A15%3A00
>
> test _int ... FAILED 649 ms
>
> = pgsql.build/contrib/intarray/regression.diffs
> ===
> diff -U3
> /usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/expected/_int.out
> /usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/results/_int.out
> ---
> /usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/expected/_int.out
> 2019-03-21 12:16:30.514677000 +0100
> +++
> /usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/results/_int.out
> 2019-04-05 07:23:10.005914000 +0200
> @@ -453,13 +453,13 @@
> SELECT count(*) from test__int WHERE a && '{23,50}';
> count
> ---
> - 403
> + 402
> (1 row)
>
> SELECT count(*) from test__int WHERE a @@ '23|50';
> count
> ---
> - 403
> + 402
> (1 row)
>
> Those two queries are run immediately after:
>
> CREATE INDEX text_idx on test__int using gist ( a gist__int_ops );
>
There are a couple of other recent instances of this failure, on
francolin and whelk.
cheers
andrew
--
Andrew Dunstanhttps://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Failure in contrib test _int on loach
Hi,
This is a strange failure:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach=2019-04-05%2005%3A15%3A00
test _int ... FAILED 649 ms
= pgsql.build/contrib/intarray/regression.diffs
===
diff -U3
/usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/expected/_int.out
/usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/results/_int.out
--- /usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/expected/_int.out
2019-03-21 12:16:30.514677000 +0100
+++ /usr/home/pgbf/buildroot/HEAD/pgsql.build/contrib/intarray/results/_int.out
2019-04-05 07:23:10.005914000 +0200
@@ -453,13 +453,13 @@
SELECT count(*) from test__int WHERE a && '{23,50}';
count
---
- 403
+ 402
(1 row)
SELECT count(*) from test__int WHERE a @@ '23|50';
count
---
- 403
+ 402
(1 row)
Those two queries are run immediately after:
CREATE INDEX text_idx on test__int using gist ( a gist__int_ops );
--
Thomas Munro
https://enterprisedb.com
