Horton

Re: Pluggable Storage - Andres's take

Haribabu Kommi <kommi.haribabu@gmail.com>

View thread View on postgr.es
From: Haribabu Kommi <kommi.haribabu@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-10-23T06:49:23Z
Lists: pgsql-hackers

Attachments

On Mon, Oct 22, 2018 at 6:16 PM Haribabu Kommi <kommi.haribabu@gmail.com>
wrote:

> On Thu, Oct 18, 2018 at 1:04 PM Haribabu Kommi <kommi.haribabu@gmail.com>
> wrote:
>
>> On Tue, Oct 9, 2018 at 1:46 PM Haribabu Kommi <kommi.haribabu@gmail.com>
>> wrote:
>>
>>>
>>> I also observed the failure of aggregates.sql, will look into it.
>>>
>>
>> The random failure of aggregates.sql is as follows
>>
>>   SELECT avg(a) AS avg_32 FROM aggtest WHERE a < 100;
>> !        avg_32
>> ! ---------------------
>> !  32.6666666666666667
>>   (1 row)
>>
>>   -- In 7.1, avg(float4) is computed using float8 arithmetic.
>> --- 8,16 ----
>>   (1 row)
>>
>>   SELECT avg(a) AS avg_32 FROM aggtest WHERE a < 100;
>> !  avg_32
>> ! --------
>> !
>>   (1 row)
>>
>> Same NULL result for another aggregate query on column b.
>>
>> The aggtest table is accessed by two tests that are running in parallel.
>> i.e aggregates.sql and transactions.sql, In transactions.sql, inside a
>> transaction
>> all the records in the aggtest table are deleted and aborted the
>> transaction,
>> I suspect that some visibility checks are having some race conditions
>> that leads
>> to no records on the table aggtest, thus it returns NULL result.
>>
>> If I try the scenario manually by opening a transaction and deleting the
>> records, the
>> issue is not occurring.
>>
>> I am yet to find the cause for this problem.
>>
>
> I am not yet able to generate a test case where the above issue can occur
> easily for
> debugging, it is happening randomly. I will try to add some logs to find
> out the problem.
>

I am able to generate the simple test and found the problem. The issue with
the following
SQL.

SELECT *
   INTO TABLE xacttest
   FROM aggtest;

During the processing of the above query, the tuple that is selected from
the aggtest is
sent to the intorel_receive() function, and the same tuple is used for the
insert, because
of this reason, the tuple xmin is updated and it leads to failure of
selecting the data from
another query. I fixed this issue by materializing the slot.

During the above test run, I found another issue during analyze, that is
trying to access
the invalid offset data. Attached a fix patch.

Regards,
Haribabu Kommi
Fujitsu Australia

Commits

  1. Add default_table_access_method to postgresql.conf.sample.

  2. tableam: Avoid relying on relation size to determine validity of tids.

  3. tableam: Don't assume that every AM uses md.c style storage.

  4. Allow pg_class xid & multixid horizons to not be set.

  5. Fix slot type issue for fuzzy distance index scan over out-of-core table AM.

  6. tableam: comment and formatting fixes.

  7. table: docs: fix typos and grammar.

  8. tableam: basic documentation.

  9. Only allow heap in a number of contrib modules.

  10. tableam: Add table_finish_bulk_insert().

  11. tableam: sample scan.

  12. tableam: bitmap table scan.

  13. tableam: Move heap specific logic from estimate_rel_size below tableam.

  14. tableam: VACUUM and ANALYZE support.

  15. tableam: relation creation, VACUUM FULL/CLUSTER, SET TABLESPACE.

  16. tableam: Support for an index build's initial table scan(s).

  17. tableam: Add table_get_latest_tid, to wrap heap_get_latest_tid.

  18. tableam: Add helper for indexes to check if a corresponding table tuples exist.

  19. tableam: Add and use table_fetch_row_version().

  20. tableam: Use in CREATE TABLE AS and CREATE MATERIALIZED VIEW.

  21. Ensure sufficient alignment for ParallelTableScanDescData in BTShared.

  22. Don't reuse slots between root and partition in ON CONFLICT ... UPDATE.

  23. Use a virtual rather than a heap slot in two places where that suffices.

  24. Store tuples for EvalPlanQual in slots, rather than as HeapTuples.

  25. Use slots in trigger infrastructure, except for the actual invocation.

  26. Store table oid and tuple's tid in tuple slots directly.

  27. Allow to use HeapTupleData embedded in [Buffer]HeapTupleTableSlot.

  28. Add ExecStorePinnedBufferHeapTuple.

  29. Add ArchiveOpts to pass options to ArchiveEntry

  30. Rename RelationData.rd_amroutine to rd_indam.

  31. Rephrase references to "time qualification".

  32. Move remaining code from tqual.[ch] to heapam.h / heapam_visibility.c.

  33. Move generic snapshot related code from tqual.h to snapmgr.h.

  34. Remove superfluous tqual.h includes.

  35. Don't duplicate parallel seqscan shmem sizing logic in nbtree.

  36. Move vacuumlazy.c into access/heap.

  37. Support parallel bitmap heap scans.