Horton

Re: Pluggable Storage - Andres's take

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Heikki Linnakangas <hlinnaka@iki.fi>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, Alvaro Herrera <alvherre@2ndquadrant.com>, David Rowley <david.rowley@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Asim R P <apraveen@pivotal.io>, pgsql-hackers@postgresql.org, Ashwin Agrawal <aagrawal@pivotal.io>, Dmitry Dolgov <9erthalion6@gmail.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>
Date: 2019-04-23T22:52:01Z
Lists: pgsql-hackers 
Hi,

On 2019-04-08 15:34:46 +0300, Heikki Linnakangas wrote:
> index_update_stats() calls RelationGetNumberOfBlocks(<table>). If the AM
> doesn't use normal data files, that won't work. I bumped into that with my
> toy implementation, which wouldn't need to create any data files, if it
> wasn't for this.

There are a few more of these:

1) index_update_stats(), computing pg_class.relpages

   Feels like the number of both heap and index blocks should be
   computed by the index build and stored in IndexInfo. That'd also get
   a bit closer towards allowing indexams not going through smgr (useful
   e.g. for memory only ones).

2) commands/analyze.c, computing pg_class.relpages

   This should imo be moved to the tableam callback. It's currently done
   a bit weirdly imo, with fdws computing relpages the callback, but
   then also returning the acquirefunc. Seems like it should entirely be
   computed as part of calling acquirefunc.

3) nodeTidscan, skipping over too large tids
   I think this should just be moved into the AMs, there's no need to
   have this in nodeTidscan.c

4) freespace.c, used for the new small-rels-have-no-fsm paths.
   That's being revised currently anyway. But I'm not particularly
   concerned even if it stays as is - freespace use is optional
   anyway. And I can't quite see an AM that doesn't want to use
   postgres' storage mechanism wanting to use freespace.c

   Therefore I'm inclined not to thouch this independent of fixing the
   others.

I think none of these are critical issues for tableam, but we should fix
them.

I'm not sure about doing so for v12 though. 1) and 3) are fairly
trivial, but 2) would involve changing the FDW interface, by changing
the AnalyzeForeignTable, AcquireSampleRowsFunc signatures. But OTOH,
we're not even in beta1.

Comments?

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.