cloud-fan commented on a change in pull request #24598: [SPARK-27699][SQL]
Partially push down disjunctive predicated in Parquet/ORC
URL: https://github.com/apache/spark/pull/24598#discussion_r284219728
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilters.scala
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@@ -527,11 +527,22 @@ private[parquet] class ParquetFilters(
}
case sources.Or(lhs, rhs) =>
+ // The Or predicate is convertible when both of its children can be
pushed down.
+ // That is to say, if one/both of the children can be partially pushed
down, the Or
+ // predicate can be partially pushed down as well.
+ //
+ // Here is an example used to explain the reason.
+ // Let's say we have
+ // (a1 AND a2) OR (b1 AND b2),
+ // a1 and b1 is convertible, while a2 and b2 is not.
+ // The predicate can be converted as
+ // (a1 OR b1) AND (a1 OR b2) AND (a2 OR b1) AND (a2 OR b2)
Review comment:
The conversion from `(a1 AND a2) OR (b1 AND b2)` to`(a1 OR b1) AND (a1 OR
b2) AND (a2 OR b1) AND (a2 OR b2)` always works no matter it's a top level
boolean expression or not.
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