Chaining transaction ops #6
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henningandersen
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Aug 23, 2023
Fixes elastic/elasticsearch-internal#497 Fixes ESQL-560 A query like `from test | sort data | limit 2 | project count` fails because `LocalToGlobalLimitAndTopNExec` planning rule adds a collecting `TopNExec` after last GATHER exchange, to perform last reduce, see ``` TopNExec[[Order[data{f}#6,ASC,LAST]],2[INTEGER]] \_ExchangeExec[GATHER,SINGLE_DISTRIBUTION] \_ProjectExec[[count{f}#4]] // <- `data` is projected away but still used by the TopN node above \_FieldExtractExec[count{f}#4] \_TopNExec[[Order[data{f}#6,ASC,LAST]],2[INTEGER]] \_FieldExtractExec[data{f}#6] \_ExchangeExec[REPARTITION,FIXED_ARBITRARY_DISTRIBUTION] \_EsQueryExec[test], query[][_doc_id{f}#9, _segment_id{f}#10, _shard_id{f}#11] ``` Unfortunately, at that stage the inputs needed by the TopNExec could have been projected away by a ProjectExec, so they could be no longer available. This PR adapts the plan as follows: - add all the projections used by the `TopNExec` to the existing `ProjectExec`, so that they are available when needed - add another ProjectExec on top of the plan, to project away the originally removed projections and preserve the query semantics This approach is a bit dangerous, because it bypasses the mechanism of input/output resolution and validation that happens on the logical plan. The alternative would be to do this manipulation on the logical plan, but it's probably hard to do, because there is no concept of Exchange at that level.
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Chaining transaction ops and walking them on commit.