Hi all, I've merged the fix to master (PR: https://github.com/apache/flink/pull/28741) This will be released with the 2.4.0 release.
@dylanhz, thanks for the ticket! Best, Fabian Am Mi., 15. Juli 2026 um 11:03 Uhr schrieb Gustavo de Morais < [email protected]>: > Hey Fabian, > > Thanks for bringing this up and looking into it. It's not great that the > behavior changed, but reverting in a next minor is a valid path. +1 to it, > and to standardizing this across functions. > > Kind regards, > Gustavo > > > On Tue, 14 Jul 2026 at 04:09, dylanhz <[email protected]> wrote: > > > Sure, I’ve opened FLINK-40141 for these functions: > > > > https://issues.apache.org/jira/browse/FLINK-40141 > > > > ---------- > > Best regards, > > dylanhz > > > > > > > > > > > 2026年7月13日 22:33，Fabian Hueske <[email protected]> 写道： > > > > > > Hi everyone, > > > > > > Thanks for the feedback so far. > > > I'll start working on this and will open a PR soon. > > > > > > @dylanhz, thanks for checking the other functions! > > > Would you mind opening a ticket for these? > > > > > > Best, Fabian > > > > > > Am Sa., 11. Juli 2026 um 10:33 Uhr schrieb dylanhz <[email protected]>: > > > > > >> Hi Fabian, > > >> > > >> +1 to align with the SQL standard and other vendors. > > >> > > >> I also noticed that IS_DECIMAL, IS_DIGIT, and IS_ALPHA return FALSE > for > > >> NULL input. They may be worth reviewing separately for consistency. > > >> > > >> > > >> ---------- > > >> Best regards, > > >> dylanhz > > >> > > >> > > >> > > >> > > >>> 2026年7月9日 21:24，Fabian Hueske <[email protected]> 写道： > > >>> > > >>> Hi folks, > > >>> > > >>> I'd like to discuss FLINK-39943 [1]. > > >>> Today, Flink's IS JSON / IS NOT JSON functions are hard-coded to > never > > >>> return NULL. > > >>> The recent Calcite 1.38.0 upgrade (FLINK-36602) changed Calcite's own > > >>> default to the standard-compliant behavior instead: IS JSON is a > > >> predicate > > >>> subject to three-valued logic and should evaluate to UNKNOWN (NULL) > > when > > >>> the input is NULL, not FALSE. > > >>> Flink currently suppresses this new Calcite default to preserve the > > old, > > >>> standards-incompatible semantics [2]. > > >>> I've checked a few other engines and all agree with the standard > here. > > >>> Oracle, PostgreSQL (16+), SQL Server (ISJSON), MySQL (JSON_VALID), > and > > >>> Snowflake (IS_OBJECT/IS_ARRAY/CHECK_JSON) all return NULL/UNKNOWN > for a > > >>> NULL input. > > >>> > > >>> Originally, Flink implemented the correct nullable behavior when the > > >>> functions were added in Flink 1.11. For Flink 1.15, this was hotfixed > > [3] > > >>> to comply with Calcite's non-null semantics. > > >>> Since Calcite fixed its definition with the 1.38 release, I'm > proposing > > >>> that we revert the Flink 1.15 hotfix, even though it's a breaking > > change. > > >>> > > >>> * PRO: standards compliance, consistency with every other engine and > > with > > >>> Calcite's own default (less surprise porting SQL from other systems), > > >>> consistency with Flink's other JSON functions which already propagate > > >> NULL, > > >>> and removing custom codegen that fights Calcite on every future > > upgrade. > > >>> * CON: it's a breaking change, most notably flipping NULL IS NOT JSON > > >> from > > >>> TRUE to NULL, which can affect existing filters, views, or NOT > > NULL-typed > > >>> computed columns/sinks built on this predicate, and there's no > > >>> compatibility flag today to ease the transition. > > >>> > > >>> This is one of several breaking side-effects of the Calcite 1.38.0 > > >>> upgrade. Hence, I'd propose treating it as a deliberate, documented > > break > > >>> targeted at the next minor version (2.4) rather than adding a > dedicated > > >>> config flag. > > >>> > > >>> Curious to hear if others agree, or see a strong case for keeping the > > >>> current NOT NULL semantics. > > >>> > > >>> Best, > > >>> Fabian > > >>> > > >>> [1] https://issues.apache.org/jira/browse/FLINK-39943 > > >>> [2] > > >>> > > >> > > > https://github.com/apache/flink/commit/8de3293e2d#diff-53c19443d4ddaabe90d0041379f3656f3d52983ae7a0226a9b23bc87675471a8R93 > > >>> [3] > > >>> > > >> > > > https://github.com/apache/flink/commit/74146c626edd7603f00a6f0c90c7fccaf2066912 > > >> > > >> > > > > >
