Horton

Re: Pluggable Storage - Andres's take

Haribabu Kommi <kommi.haribabu@gmail.com>

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From: Haribabu Kommi <kommi.haribabu@gmail.com>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-11-02T00:17:29Z
Lists: pgsql-hackers

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On Wed, Oct 31, 2018 at 9:34 PM Dmitry Dolgov <9erthalion6@gmail.com> wrote:

> > On Mon, 29 Oct 2018 at 05:56, Haribabu Kommi <kommi.haribabu@gmail.com>
> wrote:
> >
> >> This problem couldn't be reproduced on the master branch, so I've tried
> to
> >> investigate it. It comes from nodeModifyTable.c:1267, when we've got
> >> HeapTupleInvisible as a result, and this value in turn comes from
> >> table_lock_tuple. Everything points to the new way of handling
> HeapTupleUpdated
> >> result from heap_update, when table_lock_tuple call was introduced.
> Since I
> >> don't see anything similar in the master branch, can anyone clarify why
> is this
> >> lock necessary here?
> >
> >
> > In the master branch code also, there is a tuple lock that is happening
> in
> > EvalPlanQual() function, but pluggable-storage code, the lock is kept
> outside
> > and also function call rearrangements, to make it easier for the table
> access
> > methods to provide their own MVCC implementation.
>
> Yes, now I see it, thanks. Also I can confirm that the attached patch
> solves
> this issue.
>

Thanks for the testing and confirmation.


> FYI, alongside with reviewing the code changes I've ran few performance
> tests
> (that's why I hit this issue with pgbench in the first place). In case of
> high
> concurrecy so far I see small performance degradation in comparison with
> the
> master branch (about 2-5% of average latency, depending on the level of
> concurrency), but can't really say why exactly (perf just shows barely
> noticeable overhead there and there, maybe what I see is actually a
> cumulative
> impact).
>

Thanks for sharing your observation, I will also analyze and try to find
out performance
bottlenecks that are causing the overhead.

Here I attached the cumulative fixes of the patches, new API additions for
zheap and
basic outline of the documentation.

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.