Horton

Re: Optimizing nbtree ScalarArrayOp execution, allowing multi-column ordered scans, skip scan

Alexander Lakhin <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Jeff Davis <pgsql@j-davis.com>, benoit <benoit@hopsandfork.com>, Alexander Korotkov <aekorotkov@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2024-04-22T08:00:00Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Move nbtree preprocessing into new .c file.

  2. Fix nbtree lookahead overflow bug.

  3. Remove unneeded nbtree array preprocessing assert.

  4. Don't try to fix eliminated nbtree array scan keys.

  5. Remove redundant nbtree preprocessing assertions.

  6. Avoid extra lookups with nbtree array inequalities.

  7. Enhance nbtree ScalarArrayOp execution.

  8. Improvements and fixes for e0b1ee17dc

  9. Skip checking of scan keys required for directional scan in B-tree

  10. Fix btmarkpos/btrestrpos array key wraparound bug.

  11. Add nbtree high key "continuescan" optimization.

  12. Consider secondary factors during nbtree splits.

  13. Make heap TID a tiebreaker nbtree index column.

  14. Fix planning of btree index scans using ScalarArrayOpExpr quals.

  15. Fix btree stop-at-nulls logic properly.

  16. Teach btree to handle ScalarArrayOpExpr quals natively.

Hello Peter,

07.04.2024 20:18, Peter Geoghegan wrote:
> On Sun, Apr 7, 2024 at 1:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
>> SELECT * FROM t WHERE a < ANY (ARRAY[1]) AND b < ANY (ARRAY[1]);
>>
>> TRAP: failed Assert("so->numArrayKeys"), File: "nbtutils.c", Line: 560, PID: 3251267
> I immediately see what's up here. WIll fix this in the next short
> while. There is no bug here in builds without assertions, but it's
> probably best to keep the assertion, and to just make sure not to call
> _bt_preprocess_array_keys_final() unless it has real work to do.

Please look at another case, where a similar Assert (but this time in
_bt_preprocess_keys()) is triggered:
CREATE TABLE t (a text, b text);
INSERT INTO t (a, b) SELECT 'a', repeat('b', 100) FROM generate_series(1, 500) g;
CREATE INDEX t_idx ON t USING btree(a);
BEGIN;
DECLARE c CURSOR FOR SELECT a FROM t WHERE a = 'a';
FETCH FROM c;
FETCH RELATIVE 0 FROM c;

TRAP: failed Assert("so->numArrayKeys"), File: "nbtutils.c", Line: 2582, PID: 1130962

Best regards,
Alexander