pgsql: doc: Clarify the logging collector's guarantees.

doc: Clarify the logging collector's guarantees.

Presently, the documentation for logging_collector says that the
collector "is designed to never lose messages," which reads as a
stronger promise than we actually make. The collector does not
fsync the log file or retry failed writes, so log messages can go
missing after an operating system crash, power loss, or a write
error. Reword that sentence and add a note about what is not
guaranteed.

Author: Daniel Bauman <danielbaniel(at)gmail(dot)com>
Reviewed-by: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Reviewed-by: Zhenwei Shang <a934172442(at)gmail(dot)com>
Reviewed-by: Robert Treat <rob(at)xzilla(dot)net>
Discussion: https://postgr.es/m/CAMtj0_a86DdDKkW-ReVpQpqjndVS6GMrwXVpQY4G3-SGY7saMQ%40mail.gmail.com
Backpatch-through: 14

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a92fbdfb830046e907813e9067b2c9de9708d600

Modified Files
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doc/src/sgml/config.sgml | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)