Horton

Re: Pluggable Storage - Andres's take

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>
Cc: 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: 2019-04-08T12:34:46Z
Lists: pgsql-hackers

Attachments

I wrote a little toy implementation that just returns constant data to 
play with this a little. Looks good overall.

There were a bunch of typos in the comments in tableam.h, see attached. 
Some of the comments could use more copy-editing and clarification, I 
think, but I stuck to fixing just typos and such for now.

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.

The comments for relation_set_new_relfilenode() callback say that the AM 
can set *freezeXid and *minmulti to invalid. But when I did that, VACUUM 
hits this assertion:

TRAP: FailedAssertion("!(((classForm->relfrozenxid) >= ((TransactionId) 
3)))", File: "vacuum.c", Line: 1323)

There's a little bug in index-only scan executor node, where it mixes up 
the slots to hold a tuple from the index, and from the table. That 
doesn't cause any ill effects if the AM uses TTSOpsHeapTuple, but with 
my toy AM, which uses a virtual slot, it caused warnings like this from 
index-only scans:

WARNING:  problem in alloc set ExecutorState: detected write past chunk 
end in block 0x56419b0f88e8, chunk 0x56419b0f8f90

Attached is a patch with the toy implementation I used to test this. 
I'm not suggesting we should commit that - although feel free to do that 
if you think it's useful - but it shows how I bumped into these issues. 
The second patch fixes the index-only-scan slot confusion (untested, 
except with my toy AM).

- Heikki

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.