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Commit3c5d000

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Fix incorrect logic for clearing BufferDirtiedByMe in ReleaseRelationBuffers
and DropBuffers. Formerly we cleared the flag for each buffer currentlybelonging to the target rel or database, but that's completely wrong!Must look at BufferTagLastDirtied to see whether the BufferDirtiedByMeflag is relevant to target rel or not; this is *independent* of thecurrent contents of the buffer. Vadim spotted this problem, but hisfix was only partially correct...
1 parent5aeec4b commit3c5d000

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+29
-10
lines changed

1 file changed

+29
-10
lines changed

‎src/backend/storage/buffer/bufmgr.c

Lines changed: 29 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.89 2000/10/21 15:43:27 vadim Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.90 2000/10/22 20:20:49 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1567,7 +1567,6 @@ ReleaseRelationBuffers(Relation rel)
15671567
}
15681568
/* Now we can do what we came for */
15691569
bufHdr->flags &= ~(BM_DIRTY |BM_JUST_DIRTIED);
1570-
BufferDirtiedByMe[i-1]= false;
15711570

15721571
/*
15731572
* Release any refcount we may have.
@@ -1594,12 +1593,23 @@ ReleaseRelationBuffers(Relation rel)
15941593
else
15951594
{
15961595
Assert(bufHdr->relId.relId!=relid||
1597-
(bufHdr->relId.dbId!=MyDatabaseId&&
1598-
bufHdr->relId.dbId!=InvalidOid));
1599-
if (RelFileNodeEquals(rel->rd_node,
1600-
BufferTagLastDirtied[i-1].rnode))
1601-
BufferDirtiedByMe[i-1]= false;
1596+
(bufHdr->relId.dbId!=MyDatabaseId&&
1597+
bufHdr->relId.dbId!=InvalidOid));
16021598
}
1599+
1600+
/*
1601+
* Also check to see if BufferDirtiedByMe info for this buffer
1602+
* refers to the target relation, and clear it if so. This is
1603+
* independent of whether the current contents of the buffer
1604+
* belong to the target relation!
1605+
*
1606+
* NOTE: we have no way to clear BufferDirtiedByMe info in other
1607+
* backends, but hopefully there are none with that bit set for
1608+
* this rel, since we hold exclusive lock on this rel.
1609+
*/
1610+
if (RelFileNodeEquals(rel->rd_node,
1611+
BufferTagLastDirtied[i-1].rnode))
1612+
BufferDirtiedByMe[i-1]= false;
16031613
}
16041614

16051615
SpinRelease(BufMgrLock);
@@ -1652,7 +1662,6 @@ DropBuffers(Oid dbid)
16521662
}
16531663
/* Now we can do what we came for */
16541664
bufHdr->flags &= ~(BM_DIRTY |BM_JUST_DIRTIED);
1655-
BufferDirtiedByMe[i-1]= false;
16561665

16571666
/*
16581667
* The thing should be free, if caller has checked that no
@@ -1667,9 +1676,19 @@ DropBuffers(Oid dbid)
16671676
else
16681677
{
16691678
Assert(bufHdr->relId.dbId!=dbid);
1670-
if (BufferTagLastDirtied[i-1].rnode.tblNode==dbid)
1671-
BufferDirtiedByMe[i-1]= false;
16721679
}
1680+
1681+
/*
1682+
* Also check to see if BufferDirtiedByMe info for this buffer
1683+
* refers to the target database, and clear it if so. This is
1684+
* independent of whether the current contents of the buffer
1685+
* belong to the target database!
1686+
*
1687+
* (Actually, this is probably unnecessary, since I shouldn't have
1688+
* ever dirtied pages of the target database, but...)
1689+
*/
1690+
if (BufferTagLastDirtied[i-1].rnode.tblNode==dbid)
1691+
BufferDirtiedByMe[i-1]= false;
16731692
}
16741693
SpinRelease(BufMgrLock);
16751694
}

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