kaijianding commented on a change in pull request #11379:
URL: https://github.com/apache/druid/pull/11379#discussion_r662826614
##########
File path:
processing/src/main/java/org/apache/druid/query/groupby/strategy/GroupByStrategyV2.java
##########
@@ -213,7 +216,48 @@ public boolean doMergeResults(final GroupByQuery query)
context.put("finalize", false);
context.put(GroupByQueryConfig.CTX_KEY_STRATEGY,
GroupByStrategySelector.STRATEGY_V2);
context.put(CTX_KEY_OUTERMOST, false);
- if (query.getUniversalTimestamp() != null) {
+ Map<String, Object> timestampFieldContext =
GroupByQueryHelper.findTimestampResultField(query);
+ context.putAll(timestampFieldContext);
+
+ Granularity granularity = query.getGranularity();
+ List<DimensionSpec> dimensionSpecs = query.getDimensions();
+ final String timestampResultField = (String)
timestampFieldContext.get(GroupByQuery.CTX_TIMESTAMP_RESULT_FIELD);
+ final boolean hasTimestampResultField = timestampResultField != null
+ &&
query.getContextBoolean(CTX_KEY_OUTERMOST, true);
+ int timestampResultFieldIndex = 0;
+ if (hasTimestampResultField) {
+ // sql like "group by city_id,time_floor(__time to day)",
+ // the original translated query is granularity=all and dimensions:[d0,
d1]
+ // the better plan is granularity=day and dimensions:[d0]
+ // but the ResultRow structure is changed from [d0, d1] to [__time, d0]
+ // this structure should be fixed as [d0, d1] (actually it is [d0,
__time]) before postAggs are called
+ final Granularity timestampResultFieldGranularity
+ = (Granularity)
timestampFieldContext.get(GroupByQuery.CTX_TIMESTAMP_RESULT_FIELD_GRANULARITY);
+ dimensionSpecs =
+ query.getDimensions()
+ .stream()
+ .filter(dimensionSpec ->
!dimensionSpec.getOutputName().equals(timestampResultField))
+ .collect(Collectors.toList());
+ granularity = timestampResultFieldGranularity;
+ // when timestampResultField is the last dimension, should set
sortByDimsFirst=true,
+ // otherwise the downstream is sorted by row's timestamp first which
makes the final ordering not as expected
+ timestampResultFieldIndex = (int)
timestampFieldContext.get(GroupByQuery.CTX_TIMESTAMP_RESULT_FIELD_INDEX);
+ if (!query.getContextSortByDimsFirst() && timestampResultFieldIndex ==
query.getDimensions().size() - 1) {
+ context.put(GroupByQuery.CTX_KEY_SORT_BY_DIMS_FIRST, true);
+ }
+ // when timestampResultField is the first dimension and
sortByDimsFirst=true,
+ // it is actually equals to sortByDimsFirst=false
+ if (query.getContextSortByDimsFirst() && timestampResultFieldIndex == 0)
{
+ context.put(GroupByQuery.CTX_KEY_SORT_BY_DIMS_FIRST, false);
+ }
+ // when hasTimestampResultField=true and timestampResultField is neither
first nor last dimension,
+ // the DefaultLimitSpec will always do the reordering
+ }
Review comment:
I totally agree with you that better to do the planning at only one
place.
But there are so so so many related code have to be changed to be compatible
with the fact that the query.getDimensions() is with time_floor dimension
removed, like subtotalsSpec, group set, post agg, having, and many other things.
It's much much easier to make this optimization as group by inner process
improvement like fudgeTimestamp feature, and keep the sql layer not affected.
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