From: Andrew Dunstan <andrew@dunslane.net>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: make immutability tests in to_json and to_jsonb complete
Date: Tue, 17 Mar 2026 15:31:24 +0000
Message-ID: <E1w2WOB-000BJE-0h@gemulon.postgresql.org> (raw)
make immutability tests in to_json and to_jsonb complete
Complete the TODOs in to_json_is_immutable() and to_jsonb_is_immutable()
by recursing into container types (arrays, composites, ranges, multiranges,
domains) to check element/sub-type mutability, rather than conservatively
returning "mutable" for all arrays and composites.
The shared logic is factored into a single json_check_mutability() function
in jsonfuncs.c, with the existing exported functions as thin wrappers.
Composite type inspection uses lookup_rowtype_tupdesc() (typcache) instead
of relation_open() to avoid unnecessary lock acquisition in the optimizer.
Range and multirange types are now also checked recursively: if the
subtype's conversion is immutable, the range is considered immutable
for JSON purposes, even though range_out is generically marked STABLE.
This is a behavioral change: range types with immutable subtypes (e.g.,
int4range) can now appear in expression indexes via JSON_ARRAY/JSON_OBJECT,
whereas previously they were conservatively rejected.
Add regression tests for JSON_ARRAY and JSON_OBJECT mutability with
expression indexes and generated columns, covering arrays, composites,
domains, ranges, multiranges and combinations thereof.
Author: Jian He <jian.universality@gmail.com>
Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CACJufxFz=OsXQdsMJ-cqoqspD9aJrwntsQP-U2A-UaV_M+-S9g@mail.gmail.com
Commitfest: https://commitfest.postgresql.org/patch/5759
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/ecd9288624a1582a732cf86ac5a01475a1ce7815
Modified Files
--------------
src/backend/utils/adt/json.c | 38 +-------
src/backend/utils/adt/jsonb.c | 38 +-------
src/backend/utils/adt/jsonfuncs.c | 105 ++++++++++++++++++++++
src/include/utils/jsonfuncs.h | 2 +
src/test/regress/expected/sqljson.out | 165 ++++++++++++++++++++++++++++++++++
src/test/regress/sql/sqljson.sql | 89 ++++++++++++++++++
6 files changed, 367 insertions(+), 70 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: andrew@dunslane.net, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: make immutability tests in to_json and to_jsonb complete
In-Reply-To: <E1w2WOB-000BJE-0h@gemulon.postgresql.org>
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