tschwarzinger opened a new pull request, #27126:
URL: https://github.com/apache/datafusion/pull/27126

   ## Which issue does this PR close?
   
   - Related to https://github.com/apache/datafusion/issues/26169
   
   ## Rationale for this change
   
   `CoalescePartitionsExec` eagerly starts and polls streams during 
`ExecutionPlan::execute`. This can cause situtations where dynamic filters of a 
parent join are not yet available and thus the first poll of scans is done 
without the dynamic filters.
   
   This should improve 2 TPC-H queries with `pushdown_filters=true`.
   
   ## What changes are included in this PR?
   
   - Wait for the first poll to actually run the children.
   
   ## What is the testing strategy for this PR?
   
   - Existing tests
   - `inputs_start_on_first_poll_not_on_execute` asserts that the stream is not 
started 
   
   ## Are there any user-facing changes?
   
   - Could cause better pruning for some queries (as dynamic filters are 
available)
   - Possibly higher latency due to the delayed opening of files but I could 
not measure a significant impact locally.


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