9e283fc85d
Commit 27e1f1456 failed to process a pending asynchronous request made for a given ForeignScan node in postgresReScanForeignScan() (if any) in cases where we would only reset the next_tuple counter in that function, contradicting the assumption that there should be no pending asynchronous requests that have been made for async-capable subplans for the parent Append node after ReScan. This led to an assert failure in an assert-enabled build. I think this would also lead to mis-rewinding the cursor in that function in the case where we have already fetched one batch for the ForeignScan node and the asynchronous request has been made for the second batch, because even in that case we would just reset the counter when called from that function, so we would fail to execute MOVE BACKWARD ALL. To fix, modify that function to process the asynchronous request before restarting the scan. While at it, add a comment to a function to match other places. Per bug #17344 from Alexander Lakhin. Back-patch to v14 where the aforesaid commit came in. Patch by me. Test case by Alexander Lakhin, adjusted by me. Reviewed and tested by Alexander Lakhin and Dmitry Dolgov. Discussion: https://postgr.es/m/17344-226b78b00de73a7e@postgresql.org
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