Horton

Doc: add some commentary about ExecutorRun's NoMovement special case.

Tom Lane <tgl@sss.pgh.pa.us>

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Commit: 982890530379235974a7e99fd72e862ae40f1400
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2024-12-10T22:17:28Z
Releases: 18.0 
Doc: add some commentary about ExecutorRun's NoMovement special case.

Robert Haas expressed concern about whether commit 3eea7a0c9 exposed
the parallel-execution machinery to a case it isn't tested for, namely
a second non-parallel execution of a plan after a parallel execution.
Investigation shows that that can't happen because of pquery.c's
manipulation of the scan direction, but it sure wasn't obvious to
start with.  Add some commentary about that.

Discussion: https://postgr.es/m/CA+TgmoagyKQy=HFw+wLo0AKTYWHui+iKswZ8Jnqqd-cFby-WVg@mail.gmail.com

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src/backend/executor/execMain.c modified +10 −1

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