Horton

Re: Pluggable Storage - Andres's take

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Haribabu Kommi <kommi.haribabu@gmail.com>, Asim R P <apraveen@pivotal.io>, Pg Hackers <pgsql-hackers@postgresql.org>, Ashwin Agrawal <aagrawal@pivotal.io>, Alvaro Herrera <alvherre@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>
Date: 2019-03-10T04:54:07Z
Lists: pgsql-hackers 
Hi,

On 2019-03-10 05:49:26 +0100, Dmitry Dolgov wrote:
> > On Sat, Mar 9, 2019 at 4:13 AM Andres Freund <andres@anarazel.de> wrote:
> >
> > While 0001 is pretty bulky, the interesting bits concentrate on a
> > comparatively small area. I'd appreciate if somebody could give the
> > comments added in tableam.h a read (both on callbacks, and their
> > wrappers, as they have different audiences).
> 
> Potentially stupid question, but I'm curious about this one (couldn't find any
> discussion about it):

Not stupid...


>     +/*
>     + * Generic descriptor for table scans. This is the base-class for
> table scans,
>     + * which needs to be embedded in the scans of individual AMs.
>     + */
>     +typedef struct TableScanDescData
>     // ...
>     bool rs_pageatatime; /* verify visibility page-at-a-time? */
>     bool rs_allow_strat; /* allow or disallow use of access strategy */
>     bool rs_allow_sync; /* allow or disallow use of syncscan */
> 
>     + * allow_{strat, sync, pagemode} specify whether a scan strategy,
>     + * synchronized scans, or page mode may be used (although not every AM
>     + * will support those).
>     // ...
>     + TableScanDesc (*scan_begin) (Relation rel,
> 
> The last commentary makes me think that those flags (allow_strat / allow_sync /
> pageatime) are more like AM specific, shouldn't they live in HeapScanDescData?

They're common enough across AMs, but more importantly calling code
currently specifies them in several places. As they're thus essentially
generic, rather than AM specific, I think it makes sense to have them in
the general scan struct.

Greetings,

Andres Freund

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.