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>
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: 2019-04-09T13:16:54Z
Lists: pgsql-hackers

Attachments

On 08/04/2019 20:37, Andres Freund wrote:
> On 2019-04-08 15:34:46 +0300, Heikki Linnakangas wrote:
>> 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:
> 
> Hm. That's another one that I think I had fixed previously :(, and then
> concluded that it's not actually necessary for some reason. Your fix
> looks correct to me.  Do you want to commit it? Otherwise I'll look at
> it after rebasing zheap, and checking it with that.

I found another slot type confusion bug, while playing with zedstore. In 
an Index Scan, if you have an ORDER BY key that needs to be rechecked, 
so that it uses the reorder queue, then it will sometimes use the 
reorder queue slot, and sometimes the table AM's slot, for the scan 
slot. If they're not of the same type, you get an assertion:

TRAP: FailedAssertion("!(op->d.fetch.kind == slot->tts_ops)", File: 
"execExprInterp.c", Line: 1905)

Attached is a test for this, again using the toy table AM, extended to 
be able to test this. And a fix.

>> 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.
> 
> Hm, probably not a bad idea to include something like it. It seems like
> we kinda would need non-stub implementation of more functions for it to
> test much / and to serve as an example.  I'm mildy inclined to just do
> it via zheap / externally, but I'm not quite sure that's good enough.

Works for me.

>> +static Size
>> +toyam_parallelscan_estimate(Relation rel)
>> +{
>> +	ereport(ERROR,
>> +			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
>> +			 errmsg("function %s not implemented yet", __func__)));
>> +}
> 
> The other stubbed functions seem like we should require them, but I
> wonder if we should make the parallel stuff optional?

Yeah, that would be good. I would assume it to be optional.

- 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.