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https://issues.apache.org/jira/browse/CALCITE-6641?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17892352#comment-17892352
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Mihai Budiu commented on CALCITE-6641:
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The solution is to relax a bit the validator rules and to allow casts that
involve columns from the two relations in the join conditions.
> Compiling programs with ASOF joins can report obscure errors
> ------------------------------------------------------------
>
> Key: CALCITE-6641
> URL: https://issues.apache.org/jira/browse/CALCITE-6641
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.38.0
> Reporter: Mihai Budiu
> Assignee: Mihai Budiu
> Priority: Minor
>
> A program like the following:
> {code:sql}
> SELECT *
> FROM B
> LEFT ASOF JOIN S
> MATCH_CONDITION B.p_time >= S.date_time
> ON B.mod = S.key
> {code}
> can report an error such as:
> {code}
> Error in SQL statement: ASOF JOIN condition must be a conjunction of equality
> comparisons
> ON B.mod = S.key;
> ^^^^^^^^^^^^^
> {code}
> This looks like a conjunction of equality comparisons, so the error is very
> strange; internally the program represents this expression as (CAST B.mod as
> BIGINT) = S.key.
> This situation should be improved by either
> - giving an error message that explains why the compiler does not like this
> expression, or, better,
> - having the ASOF join actually accept expressions that involve casts.
> This is yet another problem caused by the new TypeCoercion improvements. When
> the ASOF join was merged there were no casts at this point in the validation.
> As was discussed briefly in [CALCITE-6639], the ASOF joins look rather
> brittle.
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