Horton

Re: remaining sql/json patches

amit <amitlangote09@gmail.com>

View thread
From: Amit Langote <amitlangote09@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew@dunslane.net>, jian he <jian.universality@gmail.com>, Erik Rijkers <er@xs4all.nl>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-11-24T09:32:06Z
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 Thu, Nov 23, 2023 at 4:38 AM Andres Freund <andres@anarazel.de> wrote:
> On 2023-11-21 12:52:35 +0900, Amit Langote wrote:
> > version     gram.o text bytes  %change  gram.c bytes  %change
> >
> > 9.6         534010             -        2108984       -
> > 10          582554             9.09     2258313       7.08
> > 11          584596             0.35     2313475       2.44
> > 12          590957             1.08     2341564       1.21
> > 13          590381            -0.09     2357327       0.67
> > 14          600707             1.74     2428841       3.03
> > 15          633180             5.40     2495364       2.73
> > 16          653464             3.20     2575269       3.20
> > 17-sqljson  672800             2.95     2709422       3.97
> >
> > So if we put SQL/JSON (including JSON_TABLE()) into 17, we end up with a gram.o 2.95% larger than v16, which granted is a somewhat larger bump, though also smaller than with some of recent releases.
>
> I think it's ok to increase the size if it's necessary increases - but I also
> think we've been a bit careless at times, and that that has made the parser
> slower.  There's probably also some "infrastructure" work we could do combat
> some of the growth too.
>
> I know I triggered the use of the .c bytes and text size, but it'd probably
> more sensible to look at the size of the important tables generated by bison.
> I think the most relevant defines are:
>
> #define YYLAST   117115
> #define YYNTOKENS  521
> #define YYNNTS  707
> #define YYNRULES  3300
> #define YYNSTATES  6255
> #define YYMAXUTOK   758
>
>
> I think a lot of the reason we end up with such a big "state transition" space
> is that a single addition to e.g. col_name_keyword or unreserved_keyword
> increases the state space substantially, because it adds new transitions to so
> many places. We're in quadratic territory, I think.  We might be able to do
> some lexer hackery to avoid that, but not sure.

One thing I noticed when looking at the raw parsing times across
versions is that they improved a bit around v12 and then some in v13:

9.0    0.000060 s
9.6    0.000061 s
10     0.000061 s
11     0.000063 s
12     0.000055 s
13     0.000054 s
15     0.000057 s
16     0.000059 s

I think they might be due to the following commits in v12 and v13 resp.:

commit c64d0cd5ce24a344798534f1bc5827a9199b7a6e
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date:   Wed Jan 9 19:47:38 2019 -0500
    Use perfect hashing, instead of binary search, for keyword lookup.
    ...
    Discussion: https://postgr.es/m/20190103163340.GA15803@britannica.bec.de

commit 7f380c59f800f7e0fb49f45a6ff7787256851a59
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date:   Mon Jan 13 15:04:31 2020 -0500
    Reduce size of backend scanner's tables.
    ...
    Discussion:
https://postgr.es/m/CACPNZCvaoa3EgVWm5yZhcSTX6RAtaLgniCPcBVOCwm8h3xpWkw@mail.gmail.com

I haven't read the whole discussions there to see if the target(s)
included the metrics you've mentioned though, either directly or
indirectly.

-- 
Thanks, Amit Langote
EDB: http://www.enterprisedb.com