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Posted to commits@calcite.apache.org by GitBox <gi...@apache.org> on 2020/03/20 10:43:31 UTC
[GitHub] [calcite] rubenada opened a new pull request #1864: [CALCITE-3829]
MergeJoinEnumerator should not use inputs enumerators until it is really
required
rubenada opened a new pull request #1864: [CALCITE-3829] MergeJoinEnumerator should not use inputs enumerators until it is really required
URL: https://github.com/apache/calcite/pull/1864
Jira ticket: [CALCITE-3829](https://issues.apache.org/jira/browse/CALCITE-3829)
`EnumerableDefaults#MergeJoinEnumerator` provides an Enumerator that performs a merge join between two sorted inputs. This sort operation can be potentially very expensive, so we should skip it if possible. Right now, merge join inputs' enumerators are created when `MergeJoinEnumerator` is constructed; however, there are some cases where we can skip the enumerator creation of one input: if the outer (i.e. left) enumerator returns no results, there is no need to access (and sort) the inner (i.e. right) enumerator. For this reason, we should delay the inner enumerator creation until the moment we are sure it is really required: when the first element of the outer enumerator is fetched.
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[GitHub] [calcite] rubenada merged pull request #1864: [CALCITE-3829]
MergeJoinEnumerator should not use inputs enumerators until it is really
required
Posted by GitBox <gi...@apache.org>.
rubenada merged pull request #1864: [CALCITE-3829] MergeJoinEnumerator should not use inputs enumerators until it is really required
URL: https://github.com/apache/calcite/pull/1864
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