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https://issues.apache.org/jira/browse/CALCITE-4375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17226397#comment-17226397
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Julian Hyde edited comment on CALCITE-4375 at 11/4/20, 9:46 PM:
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It might be better to do the CNF rewrite only in the particular rule that is
trying to push down. (I am always skeptical that there is a single best form
for an expression. Especially with CNF, which can increase the size of an
expression exponentially in the worst case.)
The rewrite might be guided by which columns come from which sides of the join.
To be clear. The method that rewrites RexNode should be in a utility such as
RexUtil or RexSimplify (not in the particular rule), and it should be unit
tested. But you should do the rewrite only inside the rule, and you should not
store the "simplified" expression in Join.condition.
was (Author: julianhyde):
It might be better to do the CNF rewrite only in the particular rule that is
trying to push down. (I am always skeptical that there is a single best form
for an expression. Especially with CNF, which can increase the size of an
expression exponentially in the worst case.)
The rewrite might be guided by which columns come from which sides of the join.
> Merge join condition that has "OR" as much as possible
> ------------------------------------------------------
>
> Key: CALCITE-4375
> URL: https://issues.apache.org/jira/browse/CALCITE-4375
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Jiatao Tao
> Assignee: Jiatao Tao
> Priority: Major
>
> SQL:
> SELECT * FROM emps,depts
> WHERE
> (emps.name = depts.name AND empno=1)
> OR
> (emps.name = depts.name AND empno=2)
>
> And the join after optimizer is:
> EnumerableNestedLoopJoin(condition=[OR(AND(=($1, $11), =($0, 1)), AND(=($1,
> $11), =($0, 2)))], joinType=[inner])
>
> In fact ($1, $11) can be extracted, and the join can be:
> HashJoin(condition=[AND(=($1, $11), OR(=($0, 1), =($0, 2)))],
> joinType=[inner])
>
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