Horton

Re: pgsql: Add more SQL/JSON constructor functions

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Peter Eisentraut <peter@eisentraut.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-07-23T12:06:33Z
Lists: pgsql-hackers

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While reviewing the patch, I found some inconsistency on json_table EXISTS.

--tested based on your patch and master.
src4=# SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a jsonb
EXISTS PATH '$'));
ERROR:  cannot cast behavior expression of type boolean to jsonb
src4=# SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a jsonb
EXISTS PATH '$' error on error));
  a
------
 true
(1 row)

Why explicitly "error on error" not report error while not explicitly
mentioning it yields an error?

"(a jsonb EXISTS PATH '$' error on error)" returns jsonb 'true'
imply that no errors happened.
so "(a jsonb EXISTS PATH '$')" should not have any errors.


but boolean cannot cast to jsonb so for JSON_TABLE,
we should reject
COLUMNS (a jsonb EXISTS PATH '$' error on error ));
COLUMNS (a jsonb EXISTS PATH '$' unknown on error ));
at an earlier stage.

because json_populate_type will use literal 'true'/'false' cast to
jsonb, which will not fail.
but JsonPathExists returns are *not* quoted true/false.
so rejecting it earlier is better than handling it at ExecEvalJsonExprPath.


attached patch trying to solve the problem, changes applied based on
your 0001, 0002.
after apply attached patch:


create domain djsonb as jsonb check(value = 'true');
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a djsonb EXISTS
PATH '$' error on error));
ERROR:  cannot cast type boolean to djsonb
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a djsonb EXISTS
PATH '$' unknown on error));
ERROR:  cannot cast type boolean to djsonb
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a jsonb EXISTS PATH '$'));
ERROR:  cannot cast type boolean to jsonb



i found out a typo in
src/test/regress/expected/sqljson_queryfuncs.out,
src/test/regress/sql/sqljson_queryfuncs.sql
"fixed-legth" should be "fixed-length"

Commits

  1. SQL/JSON: Avoid initializing unnecessary ON ERROR / ON EMPTY steps

  2. SQL/JSON: Fix default ON ERROR behavior for JSON_TABLE

  3. SQL/JSON: Fix JSON_TABLE() column deparsing

  4. Update comment about ExprState.escontext

  5. SQL/JSON: Fix casting for integer EXISTS columns in JSON_TABLE

  6. SQL/JSON: Some fixes to JsonBehavior expression casting

  7. SQL/JSON: Remove useless code in ExecInitJsonExpr()

  8. SQL/JSON: Respect OMIT QUOTES when RETURNING domains over jsonb

  9. SQL/JSON: Improve error-handling of JsonBehavior expressions

  10. SQL/JSON: Fix error-handling of some JsonBehavior expressions

  11. SQL/JSON: Rethink c2d93c3802b

  12. SQL/JSON: Always coerce JsonExpr result at runtime

  13. SQL/JSON: Fix coercion of constructor outputs to types with typmod