Hi
Current implementation of pg_flush_data when called with zero offset and zero nbytes is assumed to flush all file. In
osxit uses mmap with these arguments, but according to man:
"[EINVAL] The len argument was negative or zero. Historically, the system call would not return an
error if the argument was zero. See other potential additional restrictions in the COMPAT-
IBILITY section below."
so it is generate a lot of warnings:
"WARNING: could not mmap while flushing dirty data: Invalid argument"
Call to pg_flush_data with zero offset and nbytes happens when replica starts from base backup and fsync=on. TAP test
toreproduce is attached.
One possible solution for that is just fallback to pg_fdatasync in case when offset = nbytes = 0.
Also there are no default ifdef inside this function, is there any check that will guarantee that pg_flush_data will
notend up with empty body on some platform?
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Stas Kelvich
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company