[druid] branch master updated: disable group by config applyLimitPushDownToSegment by default (#9711)

[cw...@apache.org]

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cwylie pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/druid.git


The following commit(s) were added to refs/heads/master by this push:
     new b89ad49  disable group by config applyLimitPushDownToSegment by default (#9711)
b89ad49 is described below

commit b89ad49396387bfb931ea936a65986700ca1ff9e
Author: Clint Wylie <cw...@apache.org>
AuthorDate: Thu Apr 16 03:03:35 2020 -0700

    disable group by config applyLimitPushDownToSegment by default (#9711)
    
    * disable group by config applyLimitPushDownToSegment by default
    
    * document
---
 docs/querying/groupbyquery.md                                       | 2 +-
 .../java/org/apache/druid/query/groupby/GroupByQueryConfig.java     | 2 +-
 .../java/org/apache/druid/query/groupby/GroupByQueryConfigTest.java | 6 ++++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/docs/querying/groupbyquery.md b/docs/querying/groupbyquery.md
index a9ff9b2..27323e4 100644
--- a/docs/querying/groupbyquery.md
+++ b/docs/querying/groupbyquery.md
@@ -414,7 +414,7 @@ Supported runtime properties:
 |`druid.query.groupBy.forceHashAggregation`|Force to use hash-based aggregation.|false|
 |`druid.query.groupBy.intermediateCombineDegree`|Number of intermediate nodes combined together in the combining tree. Higher degrees will need less threads which might be helpful to improve the query performance by reducing the overhead of too many threads if the server has sufficiently powerful cpu cores.|8|
 |`druid.query.groupBy.numParallelCombineThreads`|Hint for the number of parallel combining threads. This should be larger than 1 to turn on the parallel combining feature. The actual number of threads used for parallel combining is min(`druid.query.groupBy.numParallelCombineThreads`, `druid.processing.numThreads`).|1 (disabled)|
-|`druid.query.groupBy.applyLimitPushDownToSegment`|If Broker pushes limit down to queryable nodes (historicals, peons) then limit results during segment scan.|true (enabled)|
+|`druid.query.groupBy.applyLimitPushDownToSegment`|If Broker pushes limit down to queryable data server (historicals, peons) then limit results during segment scan. If typically there are a large number of segments taking part in a query on a data server, this setting may counterintuitively reduce performance if enabled.|false (disabled)|
 
 Supported query contexts:
 
diff --git a/processing/src/main/java/org/apache/druid/query/groupby/GroupByQueryConfig.java b/processing/src/main/java/org/apache/druid/query/groupby/GroupByQueryConfig.java
index 17ca929..c31ec26 100644
--- a/processing/src/main/java/org/apache/druid/query/groupby/GroupByQueryConfig.java
+++ b/processing/src/main/java/org/apache/druid/query/groupby/GroupByQueryConfig.java
@@ -80,7 +80,7 @@ public class GroupByQueryConfig
   private boolean forcePushDownLimit = false;
 
   @JsonProperty
-  private boolean applyLimitPushDownToSegment = true;
+  private boolean applyLimitPushDownToSegment = false;
 
   @JsonProperty
   private boolean forcePushDownNestedQuery = false;
diff --git a/processing/src/test/java/org/apache/druid/query/groupby/GroupByQueryConfigTest.java b/processing/src/test/java/org/apache/druid/query/groupby/GroupByQueryConfigTest.java
index 4cb5e80..fb0090f 100644
--- a/processing/src/test/java/org/apache/druid/query/groupby/GroupByQueryConfigTest.java
+++ b/processing/src/test/java/org/apache/druid/query/groupby/GroupByQueryConfigTest.java
@@ -56,6 +56,7 @@ public class GroupByQueryConfigTest
     Assert.assertEquals(4, config.getMaxOnDiskStorage());
     Assert.assertEquals(5, config.getMaxMergingDictionarySize());
     Assert.assertEquals(6.0, config.getBufferGrouperMaxLoadFactor(), 0.0);
+    Assert.assertFalse(config.isApplyLimitPushDownToSegment());
   }
 
   @Test
@@ -78,6 +79,7 @@ public class GroupByQueryConfigTest
     Assert.assertEquals(4, config2.getMaxOnDiskStorage());
     Assert.assertEquals(5, config2.getMaxMergingDictionarySize());
     Assert.assertEquals(6.0, config2.getBufferGrouperMaxLoadFactor(), 0.0);
+    Assert.assertFalse(config2.isApplyLimitPushDownToSegment());
   }
 
   @Test
@@ -95,7 +97,7 @@ public class GroupByQueryConfigTest
                             "maxOnDiskStorage", 0,
                             "maxResults", 2,
                             "maxMergingDictionarySize", 3,
-                            "applyLimitPushDownToSegment", false
+                            "applyLimitPushDownToSegment", true
                         )
                     )
                     .build()
@@ -109,6 +111,6 @@ public class GroupByQueryConfigTest
     Assert.assertEquals(0, config2.getMaxOnDiskStorage());
     Assert.assertEquals(3, config2.getMaxMergingDictionarySize());
     Assert.assertEquals(6.0, config2.getBufferGrouperMaxLoadFactor(), 0.0);
-    Assert.assertFalse(config2.isApplyLimitPushDownToSegment());
+    Assert.assertTrue(config2.isApplyLimitPushDownToSegment());
   }
 }


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