Github user mallman commented on a diff in the pull request:
https://github.com/apache/spark/pull/21320#discussion_r190486220
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala ---
@@ -1256,8 +1256,18 @@ object SQLConf {
"issues. Turn on this config to insert a local sort before
actually doing repartition " +
"to generate consistent repartition results. The performance of
repartition() may go " +
"down since we insert extra local sort before it.")
+ .booleanConf
+ .createWithDefault(true)
+
+ val NESTED_SCHEMA_PRUNING_ENABLED =
+ buildConf("spark.sql.nestedSchemaPruning.enabled")
+ .internal()
+ .doc("Prune nested fields from a logical relation's output which are
unnecessary in " +
+ "satisfying a query. This optimization allows columnar file format
readers to avoid " +
+ "reading unnecessary nested column data. Currently Parquet is the
only data source that " +
--- End diff --
ORC should be able to support this capability as well, but this PR does not
address that.
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