Horton

Re: remaining sql/json patches

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Nikita Malakhov <hukutoc@gmail.com>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew@dunslane.net>, Erik Rijkers <er@xs4all.nl>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-10-16T12:49:15Z
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 Mon, Oct 16, 2023 at 5:47 PM Amit Langote <amitlangote09@gmail.com> wrote:
>
> > We're currently looking into this case.
>
> Thanks for the report.  I think I've figured out the problem --
> ExecEvalJsonExprCoercion() mishandles the EMPTY ARRAY ON EMPTY case.
>
> I'm reading the other 2 patches...
>
> --
> Thanks, Amit Langote
> EDB: http://www.enterprisedb.com

query: select JSON_QUERY('[]'::jsonb, '$.mm' RETURNING text OMIT
QUOTES EMPTY ON EMPTY);

Breakpoint 2, ExecEvalJsonExpr (state=0x55e47ad685c0,
op=0x55e47ad68818, econtext=0x55e47ad682e8) at
../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:4188
4188            JsonExprState *jsestate = op->d.jsonexpr.jsestate;
(gdb) fin
Run till exit from #0  ExecEvalJsonExpr (state=0x55e47ad685c0,
    op=0x55e47ad68818, econtext=0x55e47ad682e8)
    at ../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:4188
ExecInterpExpr (state=0x55e47ad685c0, econtext=0x55e47ad682e8,
isnull=0x7ffe63659e2f) at
../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:1556
1556                            EEO_NEXT();
(gdb) p *op->resnull
$1 = true
(gdb) cont
Continuing.

Breakpoint 1, ExecEvalJsonExprCoercion (state=0x55e47ad685c0,
op=0x55e47ad68998, econtext=0x55e47ad682e8, res=94439801785192,
resnull=false) at
../../Desktop/pg_sources/main/postgres/src/backend/executor/execExprInterp.c:4453
4453    {
(gdb) i args
state = 0x55e47ad685c0
op = 0x55e47ad68998
econtext = 0x55e47ad682e8
res = 94439801785192
resnull = false
(gdb) p *op->resnull
$2 = false
-------------------------------------------------------
in ExecEvalJsonExpr, *op->resnull is true.
then in ExecEvalJsonExprCoercion *op->resnull is false.
I am not sure why *op->resnull value changes, when changes.
-------------------------------------------------------
in ExecEvalJsonExprCoercion, if resnull is true, then jb is null, but
it seems there is no code to handle the case.
-----------------------------
add the following code after ExecEvalJsonExprCoercion if
(!InputFunctionCallSafe(...) works, but seems like a hack.

if (!val_string)
{
*op->resnull = true;
*op->resvalue = (Datum) 0;
}