leventov commented on a change in pull request #8209: add mechanism to control
filter optimization in historical query processing
URL: https://github.com/apache/incubator-druid/pull/8209#discussion_r311688559
##########
File path:
processing/src/main/java/org/apache/druid/segment/filter/Filters.java
##########
@@ -651,4 +652,31 @@ private static void generateAllCombinations(
generateAllCombinations(result, andList.subList(1, andList.size()),
nonAndList);
}
}
+
+ /**
+ * This method provides a "standard" implementation of {@link
Filter#shouldUseIndex(BitmapIndexSelector)} which takes
+ * a {@link Filter}, a {@link BitmapIndexSelector}, and {@link FilterTuning}
to determine if:
+ * a) the filter supports bitmap indexes
+ * b) the filter tuning specifies that it should use the index
+ * c) the cardinality of the column is above the minimum threshold and
below the maximum threshold to use the index
+ *
+ * If all these things are true, {@link
org.apache.druid.segment.QueryableIndexStorageAdapter} will utilize the
+ * indexes.
+ */
+ public static boolean shouldUseIndex(
+ Filter filter,
+ BitmapIndexSelector indexSelector,
+ @Nullable FilterTuning filterTuning
+ )
+ {
+ final FilterTuning tuning = filterTuning != null ? filterTuning :
FilterTuning.createDefault(filter, indexSelector);
+ if (filter.supportsBitmapIndex(indexSelector) && tuning.getUseIndex()) {
+ return filter.getRequiredColumns().stream().allMatch(column -> {
+ final int cardinality =
indexSelector.getBitmapIndex(column).getCardinality();
Review comment:
It's not obvious that `filter.supportsBitmapIndex(indexSelector)` above
guarantees that `indexSelector.getBitmapIndex(column)` is non-null for every
column. If it does, please add the corresponding mandate in the Javadoc for
`supportsBitmapIndex()`. If it doesn't please add a null guard.
Please also annotate `BitmapIndexSelector.supportsBitmapIndex()` as
`@Nullable`.
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