Horton

Re: Pluggable Storage - Andres's take

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Amit Khandekar <amitdkhan.pg@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Haribabu Kommi <kommi.haribabu@gmail.com>, Asim R P <apraveen@pivotal.io>, Pg Hackers <pgsql-hackers@postgresql.org>, Ashwin Agrawal <aagrawal@pivotal.io>, Dmitry Dolgov <9erthalion6@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>
Date: 2019-02-20T22:46:50Z
Lists: pgsql-hackers 
On Fri, Feb 8, 2019 at 5:18 AM Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
> In the attached v1 patch, the prefetch_distance is calculated as
> effective_io_concurrency + 10. Also it has some cosmetic changes.

I did a little brief review of this patch and noticed the following things.

+} PrefetchState;

That name seems too generic.

+/*
+ * An arbitrary way to come up with a pre-fetch distance that grows with io
+ * concurrency, but is at least 10 and not more than the max effective io
+ * concurrency.
+ */

This comment is kinda useless, because it only tells us what the code
does (which is obvious anyway) and not why it does that.  Saying that
your formula is arbitrary may not be the best way to attract support
for it.

+ for (i = prefetch_state->next_item; i < nitems && count < prefetch_count; i++)

It looks strange to me that next_item is stored in prefetch_state and
nitems is passed around as an argument.  Is there some reason why it's
like that?

+ /* prefetch a fixed number of pages beforehand. */

Not accurate -- the number of pages we prefetch isn't fixed.  It
depends on effective_io_concurrency.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.