SQL/JSON: Some fixes to JsonBehavior expression casting

1. Remove the special case handling when casting the JsonBehavior
   expressions to types with typmod, like 86d33987 did for the casting
   of SQL/JSON constructor functions.

2. Fix casting for fixed-length character and bit string types by
   using assignment-level casts.  This is again similar to what
   86d33987 did, but for ON ERROR / EMPTY expressions.

3. Use runtime coercion for the boolean ON ERROR constants so that
   using fixed-length character string types, for example, for an
   EXISTS column doesn't cause a "value too long for type
   character(n)" when the parser tries to coerce the default ON ERROR
   value "false" to that type, that is, even when clause is not
   specified.

4. Simplify the conditions of when to use runtime coercion vs
   creating the cast expression in the parser itself.  jsonb-valued
   expressions are now always coerced at runtime and boolean
   expressions too if the target type is a string type for the
   reasons mentioned above.

New tests are from a patch that Jian He posted.  Outputs of some
existing tests change because the coercion now happens at runtime
instead of at parse time.

Reported-by: Jian He <jian.universality@gmail.com>
Author: Jian He <jian.universality@gmail.com>
Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com
Backpatch-through: 17
This commit is contained in:
Amit Langote
2024-07-30 10:37:56 +09:00
parent f208a16035
commit 847ee701bd
5 changed files with 164 additions and 52 deletions

View File

@ -266,7 +266,10 @@ SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int4 EXISTS PATH '$.a'));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int2 EXISTS PATH '$.a'));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int8 EXISTS PATH '$.a'));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a float4 EXISTS PATH '$.a'));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a char(5) EXISTS PATH '$.a'));
-- Default FALSE (ON ERROR) doesn't fit char(3)
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a char(3) EXISTS PATH '$.a'));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a char(3) EXISTS PATH '$.a' ERROR ON ERROR));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a char(5) EXISTS PATH '$.a' ERROR ON ERROR));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a json EXISTS PATH '$.a'));
SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a jsonb EXISTS PATH '$.a'));