Re: wal_consistency_checking reports an inconsistency on master branch
On 2018-04-30 22:08:46 -0700, Andres Freund wrote: > On 2018-04-23 07:58:30 -0700, Andres Freund wrote: > > On 2018-04-23 13:22:21 +0300, Heikki Linnakangas wrote: > > > On 13/04/18 13:08, Michael Paquier wrote: > > > > On Fri, Apr 13, 2018 at 02:15:35PM +0530, amul sul wrote: > > > > > I have looked into this and found that the issue is in > > > > > heap_xlog_delete -- we > > > > > have missed to set the correct offset number from the target_tid when > > > > > XLH_DELETE_IS_PARTITION_MOVE flag is set. > > > > > > > > Oh, this looks good to me. So when a row was moved across partitions > > > > this could have caused incorrect tuple references on a standby, which > > > > could have caused corruptions. > > > > > > Hmm. So, the problem was that HeapTupleHeaderSetMovedPartitions() only > > > sets > > > the block number to InvalidBlockNumber, and leaves the offset number > > > unchanged. WAL replay didn't preserve the offset number, so the master and > > > the standby had a different offset number in the ctid. > > > > Right. > > > > > Why does HeapTupleHeaderSetMovedPartitions() leave the offset number > > > unchanged? The old offset number is meaningless without the block number. > > > Also, bits and magic values in the tuple header are scarce. We're > > > squandering a whole range of values in the ctid, everything with > > > ip_blkid==InvalidBlockNumber, to mean "moved to different partition", > > > when a > > > single value would suffice. > > > > Yes, I agree on that. > > > > > > > I kept using InvalidBlockNumber there, so ItemPointerIsValid() still > > > considers those item pointers as invalid. But my gut feeling is actually > > > that it would be better to use e.g. 0 as the block number, so that these > > > item pointers would appear valid. Again, to follow the precedent of > > > speculative insertion tokens. But I'm not sure if there was some > > > well-thought-out reason to make them appear invalid. A comment on that > > > would > > > be nice, at least. > > > > That seems risky to me. We want something that stops EPQ style chasing > > without running into asserts for invalid offsets... > > Heikki, would you rather apply this yourself or have me do it? I pushed that now. Greetings, Andres Freund
Re: wal_consistency_checking reports an inconsistency on master branch
On 2018-04-23 07:58:30 -0700, Andres Freund wrote: > On 2018-04-23 13:22:21 +0300, Heikki Linnakangas wrote: > > On 13/04/18 13:08, Michael Paquier wrote: > > > On Fri, Apr 13, 2018 at 02:15:35PM +0530, amul sul wrote: > > > > I have looked into this and found that the issue is in heap_xlog_delete > > > > -- we > > > > have missed to set the correct offset number from the target_tid when > > > > XLH_DELETE_IS_PARTITION_MOVE flag is set. > > > > > > Oh, this looks good to me. So when a row was moved across partitions > > > this could have caused incorrect tuple references on a standby, which > > > could have caused corruptions. > > > > Hmm. So, the problem was that HeapTupleHeaderSetMovedPartitions() only sets > > the block number to InvalidBlockNumber, and leaves the offset number > > unchanged. WAL replay didn't preserve the offset number, so the master and > > the standby had a different offset number in the ctid. > > Right. > > > Why does HeapTupleHeaderSetMovedPartitions() leave the offset number > > unchanged? The old offset number is meaningless without the block number. > > Also, bits and magic values in the tuple header are scarce. We're > > squandering a whole range of values in the ctid, everything with > > ip_blkid==InvalidBlockNumber, to mean "moved to different partition", when a > > single value would suffice. > > Yes, I agree on that. > > > > I kept using InvalidBlockNumber there, so ItemPointerIsValid() still > > considers those item pointers as invalid. But my gut feeling is actually > > that it would be better to use e.g. 0 as the block number, so that these > > item pointers would appear valid. Again, to follow the precedent of > > speculative insertion tokens. But I'm not sure if there was some > > well-thought-out reason to make them appear invalid. A comment on that would > > be nice, at least. > > That seems risky to me. We want something that stops EPQ style chasing > without running into asserts for invalid offsets... Heikki, would you rather apply this yourself or have me do it? Greetings, Andres Freund
Re: wal_consistency_checking reports an inconsistency on master branch
As a general note on this thread, we should try to get this cleared up as soon as possible, since it involves an on-disk format change. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
Re: wal_consistency_checking reports an inconsistency on master branch
On Mon, Apr 23, 2018 at 07:58:30AM -0700, Andres Freund wrote: > On 2018-04-23 13:22:21 +0300, Heikki Linnakangas wrote: >> Why does HeapTupleHeaderSetMovedPartitions() leave the offset number >> unchanged? The old offset number is meaningless without the block number. >> Also, bits and magic values in the tuple header are scarce. We're >> squandering a whole range of values in the ctid, everything with >> ip_blkid==InvalidBlockNumber, to mean "moved to different partition", when a >> single value would suffice. > > Yes, I agree on that. True that the spculative inserts and the partition move are handled in inconsistent ways now. >> I kept using InvalidBlockNumber there, so ItemPointerIsValid() still >> considers those item pointers as invalid. But my gut feeling is actually >> that it would be better to use e.g. 0 as the block number, so that these >> item pointers would appear valid. Again, to follow the precedent of >> speculative insertion tokens. But I'm not sure if there was some >> well-thought-out reason to make them appear invalid. A comment on that would >> be nice, at least. > > That seems risky to me. We want something that stops EPQ style chasing > without running into asserts for invalid offsets... -/* - * Special value used in t_ctid.ip_posid, to indicate that it holds a - * speculative insertion token rather than a real TID. This must be -higher - * than MaxOffsetNumber, so that it can be distinguished from a valid - * offset number in a regular item pointer. - */ -#define SpecTokenOffsetNumber 0xfff Moving those definitions from htup_details.h to itemptr.h seems confusing for me. As those are heap-related operations, I would recommend to keep them where they are, and also move those two ones to htup_details.h, renaming them on the way so as they are more -consistent: - ItemPointerIndicatesMovedPartitions - ItemPointerSetMovedPartitions -- Michael signature.asc Description: PGP signature
Re: wal_consistency_checking reports an inconsistency on master branch
On 2018-04-23 13:22:21 +0300, Heikki Linnakangas wrote: > On 13/04/18 13:08, Michael Paquier wrote: > > On Fri, Apr 13, 2018 at 02:15:35PM +0530, amul sul wrote: > > > I have looked into this and found that the issue is in heap_xlog_delete > > > -- we > > > have missed to set the correct offset number from the target_tid when > > > XLH_DELETE_IS_PARTITION_MOVE flag is set. > > > > Oh, this looks good to me. So when a row was moved across partitions > > this could have caused incorrect tuple references on a standby, which > > could have caused corruptions. > > Hmm. So, the problem was that HeapTupleHeaderSetMovedPartitions() only sets > the block number to InvalidBlockNumber, and leaves the offset number > unchanged. WAL replay didn't preserve the offset number, so the master and > the standby had a different offset number in the ctid. Right. > Why does HeapTupleHeaderSetMovedPartitions() leave the offset number > unchanged? The old offset number is meaningless without the block number. > Also, bits and magic values in the tuple header are scarce. We're > squandering a whole range of values in the ctid, everything with > ip_blkid==InvalidBlockNumber, to mean "moved to different partition", when a > single value would suffice. Yes, I agree on that. > I kept using InvalidBlockNumber there, so ItemPointerIsValid() still > considers those item pointers as invalid. But my gut feeling is actually > that it would be better to use e.g. 0 as the block number, so that these > item pointers would appear valid. Again, to follow the precedent of > speculative insertion tokens. But I'm not sure if there was some > well-thought-out reason to make them appear invalid. A comment on that would > be nice, at least. That seems risky to me. We want something that stops EPQ style chasing without running into asserts for invalid offsets... Greetings, Andres Freund
Re: wal_consistency_checking reports an inconsistency on master branch
On 13/04/18 13:08, Michael Paquier wrote:
On Fri, Apr 13, 2018 at 02:15:35PM +0530, amul sul wrote:
I have looked into this and found that the issue is in heap_xlog_delete -- we
have missed to set the correct offset number from the target_tid when
XLH_DELETE_IS_PARTITION_MOVE flag is set.
Oh, this looks good to me. So when a row was moved across partitions
this could have caused incorrect tuple references on a standby, which
could have caused corruptions.
Hmm. So, the problem was that HeapTupleHeaderSetMovedPartitions() only
sets the block number to InvalidBlockNumber, and leaves the offset
number unchanged. WAL replay didn't preserve the offset number, so the
master and the standby had a different offset number in the ctid.
Why does HeapTupleHeaderSetMovedPartitions() leave the offset number
unchanged? The old offset number is meaningless without the block
number. Also, bits and magic values in the tuple header are scarce.
We're squandering a whole range of values in the ctid, everything with
ip_blkid==InvalidBlockNumber, to mean "moved to different partition",
when a single value would suffice.
Let's tighten that up. In the attached (untested) patch, I changed the
macros so that "moved to different partition" is indicated by the magic
TID (InvalidBlockNumber, 0xfffd). Offset number 0xfffe was already used
for speculative insertion tokens, so this follows that precedent.
I kept using InvalidBlockNumber there, so ItemPointerIsValid() still
considers those item pointers as invalid. But my gut feeling is actually
that it would be better to use e.g. 0 as the block number, so that these
item pointers would appear valid. Again, to follow the precedent of
speculative insertion tokens. But I'm not sure if there was some
well-thought-out reason to make them appear invalid. A comment on that
would be nice, at least.
(Amit hinted at this in
https://www.postgresql.org/message-id/CAA4eK1KtsTqsGDggDCrz2O9Jgo7ma-Co-B8%2Bv3L2zWMA2NHm6A%40mail.gmail.com.
He was OK with the current approach, but I feel pretty strongly that we
should also set the offset number.)
- Heikki
diff --git a/src/include/access/htup_details.h b/src/include/access/htup_details.h
index cf56d4ace4..1867a70f6f 100644
--- a/src/include/access/htup_details.h
+++ b/src/include/access/htup_details.h
@@ -83,13 +83,15 @@
*
* A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid
* is initialized with its own TID (location). If the tuple is ever updated,
- * its t_ctid is changed to point to the replacement version of the tuple or
- * the block number (ip_blkid) is invalidated if the tuple is moved from one
- * partition to another partition relation due to an update of the partition
- * key. Thus, a tuple is the latest version of its row iff XMAX is invalid or
+ * its t_ctid is changed to point to the replacement version of the tuple. Or
+ * if the tuple is moved from one partition to another, due to an update of
+ * the partition key, t_ctid is set to a special value to indicate that
+ * (see ItemPointerSetMovedPartitions). Thus, a tuple is the latest version
+ * of its row iff XMAX is invalid or
* t_ctid points to itself (in which case, if XMAX is valid, the tuple is
* either locked or deleted). One can follow the chain of t_ctid links
- * to find the newest version of the row. Beware however that VACUUM might
+ * to find the newest version of the row, unless it was moved to a different
+ * partition. Beware however that VACUUM might
* erase the pointed-to (newer) tuple before erasing the pointing (older)
* tuple. Hence, when following a t_ctid link, it is necessary to check
* to see if the referenced slot is empty or contains an unrelated tuple.
@@ -288,14 +290,6 @@ struct HeapTupleHeaderData
#define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */
/*
- * Special value used in t_ctid.ip_posid, to indicate that it holds a
- * speculative insertion token rather than a real TID. This must be higher
- * than MaxOffsetNumber, so that it can be distinguished from a valid
- * offset number in a regular item pointer.
- */
-#define SpecTokenOffsetNumber 0xfffe
-
-/*
* HeapTupleHeader accessor macros
*
* Note: beware of multiple evaluations of "tup" argument. But the Set
@@ -447,11 +441,12 @@ do { \
ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \
)
-#define HeapTupleHeaderSetMovedPartitions(tup) \
- ItemPointerSetMovedPartitions(&(tup)->t_ctid)
-
#define HeapTupleHeaderIndicatesMovedPartitions(tup) \
- ItemPointerIndicatesMovedPartitions(&tup->t_ctid)
+ (ItemPointerGetOffsetNumber(&(tup)->t_ctid) == MovedPartitionsOffsetNumber && \
+ ItemPointerGetBlockNumberNoCheck(&(tup)->t_ctid) == MovedPartitionsBlockNumber)
+
+#define HeapTupleHeaderSetMovedPartitions(tup) \
+ ItemPointerSet(&(tup)->t_ctid, MovedPartitionsBlockNumber, MovedPartitionsOffsetNumber)
#define HeapTupleHeaderGetDatumLength(tup) \
VARSIZE(tup)
diff --git a/src/include
Re: wal_consistency_checking reports an inconsistency on master branch
On 2018/04/13 19:08, Michael Paquier wrote: > On Fri, Apr 13, 2018 at 02:15:35PM +0530, amul sul wrote: >> I have looked into this and found that the issue is in heap_xlog_delete -- we >> have missed to set the correct offset number from the target_tid when >> XLH_DELETE_IS_PARTITION_MOVE flag is set. > > Oh, this looks good to me. So when a row was moved across partitions > this could have caused incorrect tuple references on a standby, which > could have caused corruptions. > > wal_consistency_checking is proving to be worth its cost here... +1 Thanks, Amit
Re: wal_consistency_checking reports an inconsistency on master branch
On Fri, Apr 13, 2018 at 02:15:35PM +0530, amul sul wrote: > I have looked into this and found that the issue is in heap_xlog_delete -- we > have missed to set the correct offset number from the target_tid when > XLH_DELETE_IS_PARTITION_MOVE flag is set. Oh, this looks good to me. So when a row was moved across partitions this could have caused incorrect tuple references on a standby, which could have caused corruptions. wal_consistency_checking is proving to be worth its cost here... -- Michael signature.asc Description: PGP signature
Re: wal_consistency_checking reports an inconsistency on master branch
On Fri, Apr 13, 2018 at 9:06 AM, Andres Freund wrote:
> On 2018-04-13 12:29:21 +0900, Amit Langote wrote:
>> On 2018/04/13 7:36, Peter Geoghegan wrote:
>> > On Thu, Apr 12, 2018 at 11:47 AM, Peter Geoghegan wrote:
>> >> In short, it looks like the tests added to update.sql by commit
>> >> 2f178441 ("Allow UPDATE to move rows between partitions") lead to this
>> >> failure, since I always hit a problem when update.sql is reached. I
>> >> haven't gone to the trouble of digging any deeper than that just yet.
>> >
>> > Without having looked at it in much detail, this seems rather more
>> > likely to be the fault of 2f178441. That was recent enough that it's
>> > easy to believe that I'd be the first to notice it, and actually has
>> > on-disk changes, in the form of ItemPointerSetMovedPartitions().
>>
>> I think you meant f16241bef7cc2 (Raise error when affecting tuple moved
>> into different partition), because it's the one that adds
>> ItemPointerSetMovedPartitions. Commit 2f178441 you quoted added the test
>> that triggered the failure.
>
> Right. Amul, have you looked at this?
>
I have looked into this and found that the issue is in heap_xlog_delete -- we
have missed to set the correct offset number from the target_tid when
XLH_DELETE_IS_PARTITION_MOVE flag is set.
Please find the attached patch does the correction and a big thanks to
Peter for the bug report.
Regards,
Amul
fix_installcheck_failure_due_to_MovedPartitions.patch
Description: Binary data
Re: wal_consistency_checking reports an inconsistency on master branch
Will look into this, thanks.
Regards,
Amul
Sent from a mobile device. Please excuse brevity and tpyos.
On Fri, Apr 13, 2018, 9:06 AM Andres Freund wrote:
> On 2018-04-13 12:29:21 +0900, Amit Langote wrote:
> > On 2018/04/13 7:36, Peter Geoghegan wrote:
> > > On Thu, Apr 12, 2018 at 11:47 AM, Peter Geoghegan wrote:
> > >> In short, it looks like the tests added to update.sql by commit
> > >> 2f178441 ("Allow UPDATE to move rows between partitions") lead to this
> > >> failure, since I always hit a problem when update.sql is reached. I
> > >> haven't gone to the trouble of digging any deeper than that just yet.
> > >
> > > Without having looked at it in much detail, this seems rather more
> > > likely to be the fault of 2f178441. That was recent enough that it's
> > > easy to believe that I'd be the first to notice it, and actually has
> > > on-disk changes, in the form of ItemPointerSetMovedPartitions().
> >
> > I think you meant f16241bef7cc2 (Raise error when affecting tuple moved
> > into different partition), because it's the one that adds
> > ItemPointerSetMovedPartitions. Commit 2f178441 you quoted added the test
> > that triggered the failure.
>
> Right. Amul, have you looked at this?
>
> Greetings,
>
> Andres Freund
>
Re: wal_consistency_checking reports an inconsistency on master branch
On 2018-04-13 12:29:21 +0900, Amit Langote wrote:
> On 2018/04/13 7:36, Peter Geoghegan wrote:
> > On Thu, Apr 12, 2018 at 11:47 AM, Peter Geoghegan wrote:
> >> In short, it looks like the tests added to update.sql by commit
> >> 2f178441 ("Allow UPDATE to move rows between partitions") lead to this
> >> failure, since I always hit a problem when update.sql is reached. I
> >> haven't gone to the trouble of digging any deeper than that just yet.
> >
> > Without having looked at it in much detail, this seems rather more
> > likely to be the fault of 2f178441. That was recent enough that it's
> > easy to believe that I'd be the first to notice it, and actually has
> > on-disk changes, in the form of ItemPointerSetMovedPartitions().
>
> I think you meant f16241bef7cc2 (Raise error when affecting tuple moved
> into different partition), because it's the one that adds
> ItemPointerSetMovedPartitions. Commit 2f178441 you quoted added the test
> that triggered the failure.
Right. Amul, have you looked at this?
Greetings,
Andres Freund
Re: wal_consistency_checking reports an inconsistency on master branch
On 2018/04/13 7:36, Peter Geoghegan wrote:
> On Thu, Apr 12, 2018 at 11:47 AM, Peter Geoghegan wrote:
>> In short, it looks like the tests added to update.sql by commit
>> 2f178441 ("Allow UPDATE to move rows between partitions") lead to this
>> failure, since I always hit a problem when update.sql is reached. I
>> haven't gone to the trouble of digging any deeper than that just yet.
>
> Without having looked at it in much detail, this seems rather more
> likely to be the fault of 2f178441. That was recent enough that it's
> easy to believe that I'd be the first to notice it, and actually has
> on-disk changes, in the form of ItemPointerSetMovedPartitions().
I think you meant f16241bef7cc2 (Raise error when affecting tuple moved
into different partition), because it's the one that adds
ItemPointerSetMovedPartitions. Commit 2f178441 you quoted added the test
that triggered the failure.
Thanks,
Amit
Re: wal_consistency_checking reports an inconsistency on master branch
On Thu, Apr 12, 2018 at 03:36:12PM -0700, Peter Geoghegan wrote: > Without having looked at it in much detail, this seems rather more > likely to be the fault of 2f178441. That was recent enough that it's > easy to believe that I'd be the first to notice it, and actually has > on-disk changes, in the form of ItemPointerSetMovedPartitions(). Since f16241be the following comment has been added to heap_mask(): /* * NB: Not ignoring ctid changes due to the tuple having moved * (i.e. HeapTupleHeaderIndicatesMovedPartitions), because that's * important information that needs to be in-sync between primary * and standby, and thus is WAL logged. */ And actually, if you remove this query from update.sql, then the consistency checks are able to finish: UPDATE upview set c = 120 WHERE b = 4; This triggers in the test suite a CHECK violation but this should not result in a row being moved as even c is updated it would remain on the same child partition so no rows are moved across partitions here. Could this be pointing to an older issue? -- Michael signature.asc Description: PGP signature
Re: wal_consistency_checking reports an inconsistency on master branch
On Thu, Apr 12, 2018 at 11:47 AM, Peter Geoghegan wrote:
> In short, it looks like the tests added to update.sql by commit
> 2f178441 ("Allow UPDATE to move rows between partitions") lead to this
> failure, since I always hit a problem when update.sql is reached. I
> haven't gone to the trouble of digging any deeper than that just yet.
Without having looked at it in much detail, this seems rather more
likely to be the fault of 2f178441. That was recent enough that it's
easy to believe that I'd be the first to notice it, and actually has
on-disk changes, in the form of ItemPointerSetMovedPartitions().
--
Peter Geoghegan
