Horton

Re: BitmapHeapScan streaming read user and prelim refactoring

Tomas Vondra <tomas.vondra@enterprisedb.com>

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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Andres Freund <andres@anarazel.de>, Pg Hackers <pgsql-hackers@postgresql.org>, Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: 2024-03-29T11:05:15Z
Lists: pgsql-hackers 

On 3/29/24 02:12, Thomas Munro wrote:
> On Fri, Mar 29, 2024 at 10:43 AM Tomas Vondra
> <tomas.vondra@enterprisedb.com> wrote:
>> I think there's some sort of bug, triggering this assert in heapam
>>
>>   Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno);
> 
> Thanks for the repro.  I can't seem to reproduce it (still trying) but
> I assume this is with Melanie's v11 patch set which had
> v11-0016-v10-Read-Stream-API.patch.
> 
> Would you mind removing that commit and instead applying the v13
> stream_read.c patches[1]?  v10 stream_read.c was a little confused
> about random I/O combining, which I fixed with a small adjustment to
> the conditions for the "if" statement right at the end of
> read_stream_look_ahead().  Sorry about that.  The fixed version, with
> eic=4, with your test query using WHERE a < a, ends its scan with:
> 

I'll give that a try. Unfortunately unfortunately the v11 still has the
problem I reported about a week ago:

  ERROR:  prefetch and main iterators are out of sync

So I can't run the full benchmarks :-( but master vs. streaming read API
should work, I think.

regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Fix bitmapheapscan incorrect recheck of NULL tuples

  2. Increase default maintenance_io_concurrency to 16

  3. Separate TBM[Shared|Private]Iterator and TBMIterateResult

  4. Improve read_stream.c advice for dense streams.

  5. Increase default effective_io_concurrency to 16

  6. Delay extraction of TIDBitmap per page offsets

  7. Add lossy indicator to TBMIterateResult

  8. Move BitmapTableScan per-scan setup into a helper

  9. Add and use BitmapHeapScanDescData struct

  10. Fix bitmap table scan crash on iterator release

  11. Bitmap Table Scans use unified TBMIterator

  12. Add common interface for TBMIterators

  13. Make table_scan_bitmap_next_block() async-friendly

  14. Move EXPLAIN counter increment to heapam_scan_bitmap_next_block

  15. Refactor tidstore.c iterator buffering.

  16. BitmapHeapScan: Remove incorrect assert and reset field

  17. Change BitmapAdjustPrefetchIterator to accept BlockNumber

  18. BitmapHeapScan: Use correct recheck flag for skip_fetch

  19. BitmapHeapScan: Push skip_fetch optimization into table AM

  20. BitmapHeapScan: postpone setting can_skip_fetch

  21. BitmapHeapScan: begin scan after bitmap creation

  22. Fix EXPLAIN Bitmap heap scan to count pages with no visible tuples

  23. Remove redundant snapshot copying from parallel leader to workers

  24. Remove some obsolete smgrcloseall() calls.

  25. Remove the "snapshot too old" feature.

  26. Compute XID horizon for page level index vacuum on primary.