Fix const-folding of JSON constructors inside a simple CASE
A JSON constructor with a RETURNING clause uses a CaseTestExpr as the
placeholder for its result in the coercion expression. When such a
constructor appears in a WHEN clause of a simple CASE whose test
expression is a constant, eval_const_expressions substituted that
constant for the placeholder, so the coercion produced the CASE's test
value instead of the constructor's result. For instance,
CASE 'x' WHEN JSON_OBJECT('a': 'b' RETURNING text) THEN 1 ELSE 0 END
evaluated to 1.
To fix, keep case_val out of scope while simplifying the coercion, as
is already done for the elemexpr of an ArrayCoerceExpr.
Back-patch to v16, where the SQL/JSON constructor functions were
introduced.
Author: Richard Guo <[email protected]>
Discussion:
https://postgr.es/m/CAMbWs48A=vcfbtetkucokno1_0-cu0ambt0m07dm7vj1qyi...@mail.gmail.com
Backpatch-through: 16
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/e17df18a811e082a47d68263c154ae0385cd1494
Modified Files
--------------
src/backend/optimizer/util/clauses.c | 32 +++++++++++++++++++++++++++++++-
src/include/nodes/primnodes.h | 10 +++++-----
src/test/regress/expected/sqljson.out | 7 +++++++
src/test/regress/sql/sqljson.sql | 3 +++
4 files changed, 46 insertions(+), 6 deletions(-)
