27.04.2019 22:05, Tom Lane wrote:
Anastasia Lubennikova <a.lubennik...@postgrespro.ru> 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 <a.lubennik...@postgrespro.ru>
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 = &firststack;
@@ -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 <a.lubennik...@postgrespro.ru>
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 0000000..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 0000000..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
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -509,6 +509,7 @@ gistchoose(Relation r, Page p, IndexTuple it, /* it has compressed entry */
{
/* we didn't make the random choice yet for this old best */
keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+ keep_current_best = 0; /* FIXME only for debugging */
}
if (keep_current_best == 0)
{
@@ -531,6 +532,7 @@ gistchoose(Relation r, Page p, IndexTuple it, /* it has compressed entry */
{
/* we didn't make the random choice yet for this old best */
keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+ keep_current_best = 0; /* FIXME only for debugging */
}
if (keep_current_best == 1)
break;
