Thread: pgsql: Doc: add some commentary about ExecutorRun's NoMovement special

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

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/982890530379235974a7e99fd72e862ae40f1400

Modified Files
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src/backend/executor/execMain.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)