Horton

Re: Pluggable Storage - Andres's take

Rafia Sabih <rafia.pghackers@gmail.com>

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From: Rafia Sabih <rafia.pghackers@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>, 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>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Ashwin Agrawal <aagrawal@pivotal.io>, Dmitry Dolgov <9erthalion6@gmail.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>
Date: 2019-05-07T07:45:46Z
Lists: pgsql-hackers 
On Mon, 6 May 2019 at 16:14, Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On May 6, 2019 3:40:55 AM PDT, Rafia Sabih <rafia.pghackers@gmail.com> wrote:
> >On Tue, 9 Apr 2019 at 15:17, Heikki Linnakangas <hlinnaka@iki.fi>
> >wrote:
> >>
> >> 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.
> >>
> >I was trying the toyam patch and on make check it failed with
> >segmentation fault at
> >
> >static void
> >toyam_relation_set_new_filenode(Relation rel,
> > char persistence,
> > TransactionId *freezeXid,
> > MultiXactId *minmulti)
> >{
> > *freezeXid = InvalidTransactionId;
> >
> >Basically, on running create table t (i int, j int) using toytable,
> >leads to this segmentation fault.
> >
> >Am I missing something here?
>
> I assume you got compiler warmings compiling it? The API for some callbacks changed a bit.
>
Oh yeah it does.


-- 
Regards,
Rafia Sabih

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.