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https://issues.apache.org/jira/browse/CALCITE-2288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16457254#comment-16457254
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Laurent Goujon commented on CALCITE-2288:
-----------------------------------------
I guess the simplifier cannot add back the correct type, because the
information is already lost. In that case, the type of expressions returned by
{{ReduceExpressionRule#reduceExpressionInternal}} should be correct. But
there's also a phase of simplification in that method, which is only using
{{RexSimplifier}} and not {{ExprSimplifier}}. However since CALCITE-2041,
{{RexSimplifier}} will strip a type from its nullability flag if reduced to a
literal or similar.
> Type assertion error when reducing partially constant expression
> ----------------------------------------------------------------
>
> Key: CALCITE-2288
> URL: https://issues.apache.org/jira/browse/CALCITE-2288
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Laurent Goujon
> Assignee: Julian Hyde
> Priority: Major
>
> Probably a follow up of CALCITE-2041
> The following query failed at planning time with an assertion error:
> {code:sql}
> SELECT
> EXTRACT(SECOND FROM CAST(CASE WHEN TRUE THEN {ts '2018-01-01 01:23:45'}
> ELSE NULL END AS TIMESTAMP)) =
> EXTRACT(SECOND FROM d)
> FROM (VALUES({ts '2018-01-01 01:23:45'})) tbl(d
> {code}
> Stacktrace is:
> {noformat}
> java.lang.AssertionError: Cannot add expression of different type to set:
> set type is RecordType(BOOLEAN EXPR$0) NOT NULL
> expression type is RecordType(BOOLEAN NOT NULL EXPR$0) NOT NULL
> set is
> rel#4:LogicalProject(input=HepRelVertex#3,EXPR$0==(EXTRACT(FLAG(SECOND),
> CAST(CASE(true, 2018-01-01 01:23:45, null)):TIMESTAMP(0)),
> EXTRACT(FLAG(SECOND), $0)))
> expression is LogicalProject#6
> at
> org.apache.calcite.plan.RelOptUtil.verifyTypeEquivalence(RelOptUtil.java:413)
> at
> org.apache.calcite.plan.hep.HepRuleCall.transformTo(HepRuleCall.java:57)
> at
> org.apache.calcite.plan.RelOptRuleCall.transformTo(RelOptRuleCall.java:234)
> at
> org.apache.calcite.rel.rules.ReduceExpressionsRule$ProjectReduceExpressionsRule.onMatch(ReduceExpressionsRule.java:290)
> at
> org.apache.calcite.plan.AbstractRelOptPlanner.fireRule(AbstractRelOptPlanner.java:317)
> at org.apache.calcite.plan.hep.HepPlanner.applyRule(HepPlanner.java:556)
> at
> org.apache.calcite.plan.hep.HepPlanner.applyRules(HepPlanner.java:415)
> at
> org.apache.calcite.plan.hep.HepPlanner.executeInstruction(HepPlanner.java:252)
> at
> org.apache.calcite.plan.hep.HepInstruction$RuleInstance.execute(HepInstruction.java:127)
> at
> org.apache.calcite.plan.hep.HepPlanner.executeProgram(HepPlanner.java:211)
> at
> org.apache.calcite.plan.hep.HepPlanner.findBestExp(HepPlanner.java:198)
> ...
> {noformat}
> As far as I can tell, the issue is in
> {{ReduceExpressionRules#reduceExpressions}}: when the expression is partially
> reduced, the reduced expression lost its type nullability, which is not added
> back by the simplifier.
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