somu-imply commented on code in PR #15075:
URL: https://github.com/apache/druid/pull/15075#discussion_r1348995898
##########
processing/src/main/java/org/apache/druid/query/JoinDataSource.java:
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@@ -501,20 +509,37 @@ private static Triple<DataSource, DimFilter,
List<PreJoinableClause>> flattenJoi
DimFilter currentDimFilter = null;
final List<PreJoinableClause> preJoinableClauses = new ArrayList<>();
- while (current instanceof JoinDataSource) {
- final JoinDataSource joinDataSource = (JoinDataSource) current;
- current = joinDataSource.getLeft();
- currentDimFilter = validateLeftFilter(current,
joinDataSource.getLeftFilter());
- preJoinableClauses.add(
- new PreJoinableClause(
- joinDataSource.getRightPrefix(),
- joinDataSource.getRight(),
- joinDataSource.getJoinType(),
- joinDataSource.getConditionAnalysis()
- )
- );
+ // There can be queries like
+ // Join of Unnest of Join of Unnest of Filter
+ // so these checks are needed to be ORed
+ // to get the base
+ // This also means that an addition of a new datasource
+ // Will need an instanceof check here
+ // A future work should look into if the flattenJoin
+ // can be refactored to omit these instanceof checks
+ while (current instanceof JoinDataSource || current instanceof
UnnestDataSource || current instanceof FilteredDataSource) {
+ if (current instanceof JoinDataSource) {
+ final JoinDataSource joinDataSource = (JoinDataSource) current;
+ current = joinDataSource.getLeft();
+ currentDimFilter = validateLeftFilter(current,
joinDataSource.getLeftFilter());
+ preJoinableClauses.add(
+ new PreJoinableClause(
+ joinDataSource.getRightPrefix(),
+ joinDataSource.getRight(),
+ joinDataSource.getJoinType(),
+ joinDataSource.getConditionAnalysis()
+ )
+ );
+ } else if (current instanceof UnnestDataSource) {
Review Comment:
I'll add comments. The `getAnalysis()` of an Unnest or a filteredDS always
delegates to its base. So flattening through a Join->Unnest->Join kind of
scenario makes sense to go down to find the base concrete data source. In this
PR, the filters on the filteredDataSource and unnestDataSource are not pushed
down to the left of the join, the unnest filter and the filter on the
filteredDataSource remain on the data source. I have added an unit test of
Join->Unnest->Join will add another UT of Join->Unnest->Filter->Join
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