Обсуждение: pgsql: Doc: improve discussion of race conditions involved in LISTEN.

Doc: improve discussion of race conditions involved in LISTEN.

The user docs didn't really explain how to use LISTEN safely,
so clarify that.  Also clean up some fuzzy-headed explanations
in comments.  No code changes.

Discussion: https://postgr.es/m/3ac7f397-4d5f-be8e-f354-440020675694@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d3aa114ac4de9ecc558ba77ed5c85e2ad9ad01d4

Modified Files
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doc/src/sgml/ref/listen.sgml | 31 +++++++++++++++-----
src/backend/commands/async.c | 70 ++++++++++++++++++++++++++------------------
2 files changed, 65 insertions(+), 36 deletions(-)