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Posted to gitbox@hive.apache.org by GitBox <gi...@apache.org> on 2021/07/31 10:46:53 UTC
[GitHub] [hive] dengzhhu653 commented on a change in pull request #2145: HIVE-24969: Predicates may be removed when decorrelating subqueries with lateral
dengzhhu653 commented on a change in pull request #2145:
URL: https://github.com/apache/hive/pull/2145#discussion_r680343400
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File path: ql/src/test/results/clientpositive/llap/subquery_multi.q.out
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@@ -246,7 +246,7 @@ POSTHOOK: Input: default@part_null
85768 almond antique chartreuse lavender yellow Manufacturer#1 Brand#12 LARGE BRUSHED STEEL 34 SM BAG 1753.76 refull
86428 almond aquamarine burnished black steel Manufacturer#1 Brand#12 STANDARD ANODIZED STEEL 28 WRAP BAG 1414.42 arefully
90681 almond antique chartreuse khaki white Manufacturer#3 Brand#31 MEDIUM BURNISHED TIN 17 SM CASE 1671.68 are slyly after the sl
-Warning: Shuffle Join MERGEJOIN[57][tables = [$hdt$_0, $hdt$_1, $hdt$_2, $hdt$_3]] in Stage 'Reducer 4' is a cross product
+Warning: Shuffle Join MERGEJOIN[57][tables = [$hdt$_0, $hdt$_2, $hdt$_3]] in Stage 'Reducer 4' is a cross product
Review comment:
The `$hdt$_1` is omitted because `$hdt$_0` and `$hdt$_1` perform a left semi join, that is `p_name IN (select p_name from part_null)` in `Reducer 2`, the `$hdt$_1` does not produces output after this [join](https://github.com/apache/hive/blob/23b0d30051af3ade5b03496ab9cf22929168dc84/ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java#L9109-L9118), only `$hdt$_0`, `$hdt$_2`(distinct p_brand) and `$hdt$_2`(count p_name) take place in `$hdt$_4`.
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