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Prevent re-use of a deleted relation's relfilenode until after the next

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checkpoint.  This guards against an unlikely data-loss scenario in which
we re-use the relfilenode, then crash, then replay the deletion and
recreation of the file.  Even then we'd be OK if all insertions into the
new relation had been WAL-logged ... but that's not guaranteed given all
the no-WAL-logging optimizations that have recently been added.

Patch by Heikki Linnakangas, per a discussion last month.
This commit is contained in:
Tom Lane
2007-11-15 20:36:40 +00:00
parent 7a550cb95c
commit 6cc4451b5c
5 changed files with 274 additions and 25 deletions
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29
src/backend/commands/tablespace.c
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@@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/tablespace.c,v 1.49 2007/08/01 22:45:08 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/tablespace.c,v 1.50 2007/11/15 20:36:40 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -57,6 +57,7 @@
#include "commands/comment.h"
#include "commands/tablespace.h"
#include "miscadmin.h"
#include "postmaster/bgwriter.h"
#include "storage/fd.h"
#include "utils/acl.h"
#include "utils/builtins.h"
@@ -460,13 +461,29 @@ DropTableSpace(DropTableSpaceStmt *stmt)
LWLockAcquire(TablespaceCreateLock, LW_EXCLUSIVE);
/*
* Try to remove the physical infrastructure
* Try to remove the physical infrastructure.
*/
if (!remove_tablespace_directories(tablespaceoid, false))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("tablespace \"%s\" is not empty",
tablespacename)));
{
/*
* Not all files deleted? However, there can be lingering empty files
* in the directories, left behind by for example DROP TABLE, that
* have been scheduled for deletion at next checkpoint (see comments
* in mdunlink() for details). We could just delete them immediately,
* but we can't tell them apart from important data files that we
* mustn't delete. So instead, we force a checkpoint which will clean
* out any lingering files, and try again.
*/
RequestCheckpoint(CHECKPOINT_IMMEDIATE | CHECKPOINT_FORCE | CHECKPOINT_WAIT);
if (!remove_tablespace_directories(tablespaceoid, false))
{
/* Still not empty, the files must be important then */
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("tablespace \"%s\" is not empty",
tablespacename)));
}
}
/* Record the filesystem change in XLOG */
{