Horton

Re: remaining sql/json patches

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Andrew Dunstan <andrew@dunslane.net>, Amit Langote <amitlangote09@gmail.com>, jian he <jian.universality@gmail.com>, Erik Rijkers <er@xs4all.nl>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-11-27T17:50:32Z
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.

Hi,

On 2023-11-27 15:06:12 +0100, Alvaro Herrera wrote:
> On 2023-Nov-27, Andrew Dunstan 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.

Yea, the parser table sizes are influenced by the increase in complexity of
the grammar, but it's not a trivial correlation. Bison attempts to compress
the state space and it looks like there are some heuristics involved.


> At this point one thing that IMO we cannot afford to do, is stop feature
> progress work on the name of parser speed.

Agreed - I don't think anyone advocated that though.


> But at some point we'll probably have to fix that by parsing differently (a
> top-down parser, perhaps?  Split the parser in smaller pieces that each deal
> with subsets of the whole thing?)

Yea. Both perhaps. Being able to have sub-grammars would be quite powerful I
think, and we might be able to do it without loosing cross-checking from bison
that our grammar is conflict free.  Even if the resulting combined state space
is larger, better locality should more than make up for that.



> The amount of effort spent on the parsing aspect on this thread seems in
> line with what we should always be doing: keep an eye on it, but not
> disregard the work just because the parser tables have grown.

I think we've, in other threads, not paid enough attention to it and just
added stuff to the grammar in the first way that didn't produce shift/reduce
conflicts... Of course a decent part of the problem here is the SQL standard
that so seems to like adding one-off forms of grammar (yes,
func_expr_common_subexpr, I'm looking at you)...

Greetings,

Andres Freund