Horton

Re: remaining sql/json patches

Andrew Dunstan <andrew@dunslane.net>

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From: Andrew Dunstan <andrew@dunslane.net>
To: John Naylor <johncnaylorls@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Amit Langote <amitlangote09@gmail.com>, Andres Freund <andres@anarazel.de>, jian he <jian.universality@gmail.com>, Erik Rijkers <er@xs4all.nl>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-11-28T20:49:04Z
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. SQL/JSON: Various improvements to SQL/JSON query function docs

  2. SQL/JSON: Fix some obsolete comments.

  3. SQL/JSON: Fix issues with DEFAULT .. ON ERROR / EMPTY

  4. JSON_TABLE: Add support for NESTED paths and columns

  5. Fix JsonExpr deparsing to emit QUOTES and WRAPPER correctly

  6. Fix typo introduced in 6185c9737

  7. Add basic JSON_TABLE() functionality

  8. Avoid splitting errmsg string to span multiple lines

  9. Add SQL/JSON query functions

  10. Implement various jsonpath methods

  11. Add soft error handling to some expression nodes

  12. Adjust populate_record_field() to handle errors softly

  13. Refactor code used by jsonpath executor to fetch variables

  14. Test EXPLAIN (FORMAT JSON) ... XMLTABLE

  15. Simplify productions for FORMAT JSON [ ENCODING name ]

  16. Add trailing commas to enum definitions

  17. doc: add missing <returnvalue> and whitespace

  18. Add more SQL/JSON constructor functions

  19. Rename a nonterminal used in SQL/JSON grammar

  20. Some refactoring to export json(b) conversion functions

  21. Don't include CaseTestExpr in JsonValueExpr.formatted_expr

  22. Code review for commit b6e1157e7d

  23. Pass constructName to transformJsonValueExpr()

  24. Unify JSON categorize type API and export for external use

  25. Make some indentation in gram.y consistent

  26. Allow most keywords to be used as column labels without requiring AS.

  27. Reduce size of backend scanner's tables.

  28. Use perfect hashing, instead of binary search, for keyword lookup.

On 2023-11-28 Tu 00:10, John Naylor wrote:
> On Mon, Nov 27, 2023 at 8:57 PM Andrew Dunstan <andrew@dunslane.net> wrote:
>> Interesting. But inferring a speed effect from such changes is
>> difficult. I don't have a good idea about measuring parser speed, but a
>> tool to do that would be useful. Amit has made a start on such
>> measurements, but it's only a start. I'd prefer to have evidence rather
>> than speculation.
> Tom shared this test a while back, and that's the one I've used in the
> past. The downside for a micro-benchmark like that is that it can
> monopolize the CPU cache. Cache misses in real world queries are
> likely much more dominant.
>
> https://www.postgresql.org/message-id/14616.1558560331@sss.pgh.pa.us



Cool, I took this and ran with it a bit. (See attached) Here are 
comparative timings for 1000 iterations parsing most of the 
information_schema.sql, all the way back to 9.3:


==== REL9_3_STABLE ====
Time: 3998.701 ms
==== REL9_4_STABLE ====
Time: 3987.596 ms
==== REL9_5_STABLE ====
Time: 4129.049 ms
==== REL9_6_STABLE ====
Time: 4145.777 ms
==== REL_10_STABLE ====
Time: 4140.927 ms (00:04.141)
==== REL_11_STABLE ====
Time: 4145.078 ms (00:04.145)
==== REL_12_STABLE ====
Time: 3528.625 ms (00:03.529)
==== REL_13_STABLE ====
Time: 3356.067 ms (00:03.356)
==== REL_14_STABLE ====
Time: 3401.406 ms (00:03.401)
==== REL_15_STABLE ====
Time: 3372.491 ms (00:03.372)
==== REL_16_STABLE ====
Time: 1654.056 ms (00:01.654)
==== HEAD ====
Time: 1614.949 ms (00:01.615)


This is fairly repeatable.

The first good news is that the parser is pretty fast. Even 4ms to parse 
almost all the information schema setup is pretty good.

The second piece of good news is that recent modifications have vastly 
improved the speed. So even if the changes from the SQL/JSON patches eat 
up a bit of that gain, I think we're in good shape.

In a few days I'll re-run the test with the SQL/JSON patches applied.


cheers


andrew


--
Andrew Dunstan
EDB: https://www.enterprisedb.com