Github user ilooner commented on a diff in the pull request:
https://github.com/apache/drill/pull/1101#discussion_r164611155
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/aggregate/HashAggTemplate.java
---
@@ -215,6 +206,7 @@ public BatchHolder() {
MaterializedField outputField = materializedValueFields[i];
// Create a type-specific ValueVector for this value
vector = TypeHelper.getNewVector(outputField, allocator);
+ int columnSize = new RecordBatchSizer.ColumnSize(vector).estSize;
--- End diff --
The goal of this code is to preallocate enough space to hold BATCH_SIZE
number of elements in the batch. The BatchHolder itself is used to hold the
aggregate values and aggregate values can currently only be FixedWidth vectors
or ObjectVectors. Since we know how much direct memory each of these types will
consume, we can use that knowledge in our column size estimate and preallocate
the correct amount of space.
**Note:** earlier the RecordBatchSizer would return an estSize of 0 for an
empty FixedWidth value vectors. For example and empty IntVector would return an
estSize of 0. This was incorrect behavior so I updated the RecordBatchSizer to
return the correct size of a FixedWidth vector even when the value vector is
empty. Please see the changes in the RecordBatchSizer and ValueVector templates
for more details.
---
