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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2021/10/13 23:21:40 UTC
[GitHub] [spark] c21 commented on a change in pull request #34270: [SPARK-37001][SQL] Disable two level of map for final hash aggregation by default
c21 commented on a change in pull request #34270:
URL: https://github.com/apache/spark/pull/34270#discussion_r728514936
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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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@@ -1705,11 +1705,21 @@ object SQLConf {
.doc("Enable two-level aggregate hash map. When enabled, records will first be " +
"inserted/looked-up at a 1st-level, small, fast map, and then fallback to a " +
"2nd-level, larger, slower map when 1st level is full or keys cannot be found. " +
- "When disabled, records go directly to the 2nd level.")
+ "When disabled, records go directly to the 2nd level. Enable for partial aggregate only.")
.version("2.3.0")
.booleanConf
.createWithDefault(true)
+ val ENABLE_TWOLEVEL_FINAL_AGG_MAP =
+ buildConf("spark.sql.codegen.aggregate.final.map.twolevel.enabled")
+ .internal()
+ .doc("Enable two-level aggregate hash map for final aggregate as well. Disable by default " +
+ "because final aggregate might get more distinct keys compared to partial aggregate. " +
+ "Overhead of looking up 1st-level map might dominate when having a lot of distinct keys.")
+ .version("3.2.0")
Review comment:
@cloud-fan - yes, updated.
##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
##########
@@ -1705,11 +1705,21 @@ object SQLConf {
.doc("Enable two-level aggregate hash map. When enabled, records will first be " +
"inserted/looked-up at a 1st-level, small, fast map, and then fallback to a " +
"2nd-level, larger, slower map when 1st level is full or keys cannot be found. " +
- "When disabled, records go directly to the 2nd level.")
+ "When disabled, records go directly to the 2nd level. Enable for partial aggregate only.")
.version("2.3.0")
.booleanConf
.createWithDefault(true)
+ val ENABLE_TWOLEVEL_FINAL_AGG_MAP =
+ buildConf("spark.sql.codegen.aggregate.final.map.twolevel.enabled")
Review comment:
@cloud-fan - sure, updated. So given the new meaning of config, changed the default config value to `true` as well.
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