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https://issues.apache.org/jira/browse/OPTIQ-367?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde closed OPTIQ-367.
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Close issues resolved in release 0.9.0-incubating (2014-08-25).
> PushFilterPastJoinRule should strengthen join type
> --------------------------------------------------
>
> Key: OPTIQ-367
> URL: https://issues.apache.org/jira/browse/OPTIQ-367
> Project: Optiq
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Fix For: 0.9.0-incubating
>
>
> PushFilterPashJoinRule can already convert a filter on a join into a join.
> (For example, 'FROM emp JOIN dept ON TRUE WHERE emp.deptno = emp.deptno' into
> 'FROM emp JOIN dept ON emp.deptno = dept.deptno'.)
> But if the filter is strong -- i.e. it is guaranteed to return false if one
> of its input values is NULL -- then we can upgrade the join type. For example,
> {code}
> FROM emp FULL JOIN dept WHERE emp.age > 30
> {code}
> becomes
> {code}
> FROM emp LEFT JOIN dept WHERE emp.age > 30
> {code}
> The condition is strong on emp.age, and emp.age comes from the left, so that
> if a null row is generated on the left the condition will fail. Therefore we
> can strengthen the join type to LEFT, which only generates nulls on the right.
> I also want to work on the kind of queries produced by EXISTS/IN rewrite; for
> example, the query in RelOptRulesTest.testSemiJoinRule
> {code}
> FilterRel(condition=[IS TRUE($3)])
> JoinRel(condition=[=($0, $2)], joinType=[left])
> TableAccessRel(table=[[CATALOG, SALES, DEPT]])
> AggregateRel(group=[{0}], agg#0=[MIN($1)])
> ...
> {code}
> should become
> {code}
> JoinRel(condition=[=($0, $2) AND IS TRUE($3)], joinType=[inner])
> TableAccessRel(table=[[CATALOG, SALES, DEPT]])
> AggregateRel(group=[{0}], agg#0=[MIN($1)])
> ...
> {code}
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