Hi Fabian, In general a strong +1 for the feature, without getting into the details of the FLIP yet. This is a missing feature for years and I'm happy that we're putting the time to address this - while also getting rid of some of the hard restrictions we had. Thanks!
Kind regards, Gustavo On Fri, 15 May 2026 at 16:39, Fabian Hueske <[email protected]> wrote: > Hi everyone, > > I'd like to start a discussion on FLIP-579: LATERAL SNAPSHOT Join [1]. > > Enriching a stream with data from a (slowly changing) dynamic table is a > super common use case. > Flink SQL features Temporal Joins [2] to address these use cases. > However, SQL users can only use the event-time variant which has many > limitations (heavy dependency on frequent WM updates on both inputs, > build-side table requires a PK, the join predicate must include the > build-side PK, etc). > The processing-time temporal join is disabled (due to build-side > initialization issues [3]) and temporal table function joins are > only available in Table API. > > FLIP-579 proposes a new temporal join operator that operates in > processing-time and addresses the limitations of the existing > implementations: > * initialization of the build-side before joining > * no requirement of continuous, frequent build-side WMs (after the > initialization completed) > * no requirement for a PK on the build-side > * table function-based syntax [4] via a built-in SNAPSHOT function > (proposed in FLIP-517 [4]) > > Looking forward to your feedback. > > Best, > Fabian > > [1] > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-579%3A+LATERAL+SNAPSHOT+Join > [2] > > https://nightlies.apache.org/flink/flink-docs-stable/docs/dev/table/sql/queries/joins/#temporal-joins > [3] https://issues.apache.org/jira/browse/FLINK-19830 > [4] > > https://nightlies.apache.org/flink/flink-docs-stable/docs/dev/table/sql/queries/joins/#temporal-table-function-join > [5] > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-517%3A+Better+Handling+of+Dynamic+Table+Primitives+with+PTFs#FLIP517:BetterHandlingofDynamicTablePrimitiveswithPTFs-SNAPSHOTfortemporaljoins >
