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https://issues.apache.org/jira/browse/CALCITE-6639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17892037#comment-17892037
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Steven Phillips commented on CALCITE-6639:
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Can you elaborate what exactly is the assertion error caused by?
I think we should simply not allow any optimization that results in violating
the ASOF constraint.
> Optimization that pulls up predicates causes ASOF JOIN validation failures
> --------------------------------------------------------------------------
>
> Key: CALCITE-6639
> URL: https://issues.apache.org/jira/browse/CALCITE-6639
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.38.0
> Reporter: Mihai Budiu
> Assignee: Mihai Budiu
> Priority: Minor
> Labels: pull-request-available
>
> The following test added to the RelOptRulesTest causes an assertion failure:
> {code:java}
> @Test void testAsofOpt() {
> final String sql = "SELECT *\n" +
> "FROM (VALUES (NULL, 0), (1, NULL), (1, 0), (1, 1), (1, 2), (1, 3),
> (1, 4), (2, 3), (3, 4)) AS t1(k, t)\n" +
> "ASOF JOIN (VALUES (1, NULL), (1, 2), (1, 3), (2, 10), (2, 0)) AS
> t2(k, t)\n" +
> "MATCH_CONDITION t2.t < t1.t\n" +
> "ON t1.k = t2.k\n";
> sql(sql).withRule(CoreRules.PROJECT_REDUCE_EXPRESSIONS)
> .checkUnchanged();
> }
> {code}
> This test is taken straigt from asof.iq.
> This test fails with the following assertion failure:
> {code}
> java.lang.AssertionError
> at
> org.apache.calcite.rel.metadata.RelMdPredicates$JoinConditionBasedPredicateInference.inferPredicates(RelMdPredicates.java:850)
> at
> org.apache.calcite.rel.metadata.RelMdPredicates.getPredicates(RelMdPredicates.java:346)
> at
> org.apache.calcite.rel.metadata.janino.GeneratedMetadata_PredicatesHandler.getPredicates_$(Unknown
> Source)
> at
> org.apache.calcite.rel.metadata.janino.GeneratedMetadata_PredicatesHandler.getPredicates(Unknown
> Source)
> at
> org.apache.calcite.rel.metadata.RelMetadataQuery.getPulledUpPredicates(RelMetadataQuery.java:887)
> at
> org.apache.calcite.rel.rules.ReduceExpressionsRule$ProjectReduceExpressionsRule.onMatch(ReduceExpressionsRule.java:310)
> {code}
> Diagnosis: the definition of ASOF join implementation, inspired by the
> Snowflake variant of the operation, imposes some strong "syntactical"
> constraints on the predicate structure. In particular, each predicate in the
> equi-join part must compare expressions from the two joined relations.
> These constraints ensure that the ASOF join can be efficiently implemented.
> However, this definition inhibits some optimizations, such as pull-up
> predicates, which may rewrite predicates into a shape that does not satisfy
> the above rules.
> It is not clear what the right course of action is.
> One solution would be to relax the requirements on the ASOF join and to
> validate its shape only after optimizations. But then it is not clear that
> the resulting program would always be efficiently implementable - the
> original goal of ASOF.
> Another solution would be to inhibit optimizations from optimizing such joins.
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