shaofengshi commented on a change in pull request #397: KYLIN-3722 Disable
limit push down after join
URL: https://github.com/apache/kylin/pull/397#discussion_r243876893
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File path: query/src/main/java/org/apache/kylin/query/relnode/OLAPLimitRel.java
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@@ -82,7 +82,8 @@ public void implementOLAP(OLAPImplementor implementor) {
// ignore limit after having clause
// ignore limit after another limit, e.g. select A, count(*) from
(select A,B from fact group by A,B limit 100) limit 10
// ignore limit after outer aggregate, e.g. select count(1) from
(select A,B from fact group by A,B ) limit 10
- if (!context.afterHavingClauseFilter && !context.afterLimit &&
!context.afterOuterAggregate) {
+ // ignore limit after join
+ if (!context.afterHavingClauseFilter && !context.afterLimit &&
!context.afterOuterAggregate && !context.afterJoin) {
Review comment:
My concern is, this change may make many normal queries (join with the
limit) much inefficient.
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