Cumulative 7.x backport #40195
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Cumulative 7.x backport #40195
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) When using DFS_QUERY_THEN_FETCH search type, the dfs phase is run and its results are used in the query phase to make scoring accurate. When using CCS, depending on whether the DFS phase runs in the CCS coordinating node (like if all shards were local) or in each remote cluster (when minimizing round-trips), scoring will differ. This commit disables minimizing round-trips whenever DFS is requested, as it is not currently possible to ensure that scoring is accurate in that case. Relates to elastic#32125
…ion (elastic#40056) This commit clarifies how the gateway selection works when configuring remote clusters for CCR or CCS. Specifically, it clarifies compatibility between different versions which is a very common question.
When minimizing round-trips, each cluster returns its own independent search response. In case sort by field and/or field collapsing were requested, when one cluster has no results to return, the information about the field that sorting was based on (SortField array) as well as the field (and the values) that collapsing was performed on are missing in the search response. That causes problems as we can't build the proper `TopDocs` instance which would need to be either `TopFieldDocs` or `CollapseTopFieldDocs`. The merge routine expects that all the top docs are of the same exact type which can't be guaranteed. Given that the problematic results are empty, hence have no impact on the final results, we can simply skip them. Relates to elastic#32125 Closes elastic#40067
…lastic#40101) Today a coordinating node forces a final reduction of sibling pipeline aggregators whenever reducing aggs, unless it is reducing aggs incrementally. This works well for incremental reduction of aggs, but breaks CCS when minimizing roundtrips as each cluster ends up reducing its own pipeline aggregators locally while that should only be done by the CCS coordinating node later. This causes issues as after their reduction, pipeline aggs cannot be further reduced, which is what happens with CCS causing errors like "java.lang.UnsupportedOperationException: Not supported" being returned. Each coordinating node should rather honour the reduce context flag that indicates whether we are executing a final reduce or not. If not, it should leave the sibling pipeline aggregations alone. Note that his bug affects only pipeline aggs that don't have a parent in the aggs tree, while all the others work well. Relates to elastic#40059 but does not fix it yet, as the CCS coordinating node also needs to be adapted to recreate sibling pipeline aggregators from the request.
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…astic#40177) We currently convert pipeline aggregators to their corresponding InternalAggregation instance as part of the final reduction phase. They arrive to the coordinating node as part of QuerySearchResult objects fom the shards and, despite we may incrementally reduce aggs (hence we may have some non-final reduce and the final one later) all the reduction phases happen on the same node. With CCS minimizing roundtrips though, each cluster performs its own non-final reduction, and then serializes the results back to the CCS coordinating node which will perform the final coordination. This breaks the assumptions made up until now around reductions happening all on the same node. With elastic#40101 we have made sure that top-level pipeline aggs are not reduced as part of the non-final reduction. The next step is to make sure that they don't get lost, meaning that each coordinating node needs to send them back to the CCS coordinating node as part of the top-level `InternalAggregations` object. Closes elastic#40059
Relates to elastic#40177
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This includes #40044 #40098 #39329 #40056 #40101 #40177 .
We need to disable bwc tests until the last change in the list (#40177) is backported as it requires a change in the way we serialize
InternalAggregations.