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https://issues.apache.org/jira/browse/FLINK-39420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18074062#comment-18074062
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Sergey Nuyanzin commented on FLINK-39420:
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Merged as
[1c71c3fabbe1c753634da890ec74f5ab17d7c13a|https://github.com/apache/flink/commit/1c71c3fabbe1c753634da890ec74f5ab17d7c13a]
> Temporal joins on non-lookup tables in batch mode produce a confusing
> internal error
> ------------------------------------------------------------------------------------
>
> Key: FLINK-39420
> URL: https://issues.apache.org/jira/browse/FLINK-39420
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / Planner
> Reporter: Jim Hughes
> Assignee: Jim Hughes
> Priority: Minor
> Labels: pull-request-available
>
> Temporal joins on non-lookup tables in batch mode produce a confusing
> internal error
> When a user writes a temporal join (FOR SYSTEM_TIME AS OF) against a regular
> (non-lookup) table in batch mode, the query fails with an opaque internal
> error from FlinkDecorrelateProgram:
> {code}
> org.apache.flink.table.api.TableException: unexpected correlate variable
> $cor0 in the plan
> {code}
> *Root cause:* The batch planner's TEMPORAL_JOIN_REWRITE phase only registers
> lookup join rules (LOOKUP_JOIN_WITH_FILTER / LOOKUP_JOIN_WITHOUT_FILTER).
> Non-lookup temporal joins — event-time joins on versioned tables,
> processing-time joins on non-lookup sources — leave an unresolved
> LogicalCorrelate with a LogicalSnapshot in the plan. This correlate survives
> into the decorrelation phase, which doesn't know how to handle it.
> In streaming mode these are handled by the WITH_FILTER / WITHOUT_FILTER
> rewrite rules, which are not registered in the batch rule set.
> *Example query that triggers this:*
> {code:sql}
> SELECT o.amount * r.rate
> FROM Orders AS o
> JOIN RatesHistory FOR SYSTEM_TIME AS OF o.rowtime AS r
> ON o.currency = r.currency
> {code}
> *Proposed fix:* Add a rejection rule to the batch EXPAND_PLAN_RULES that
> matches any LogicalCorrelate + LogicalSnapshot remaining after the lookup
> join rules have run, and throws a clear error:
> {quote}
> Temporal joins (FOR SYSTEM_TIME AS OF) on regular tables are not supported in
> batch mode. Use a lookup join or switch to streaming mode.
> {quote}
> The rule can unconditionally reject all remaining Correlate + Snapshot
> patterns — no lookup detection logic is needed because the lookup join rules
> fire first in the same HepProgram and rewrite valid lookup joins before the
> rejection rule sees them.
> Generated-by: Claude Opus 4.6 (1M context)
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