too-may-open-files log file entries when vauuming under solaris

Dear all,
recently we have seen a lot of occurrences of "out of file descriptors: Too many open files; release and retry" in our postgres log files, every night when a "vacuum full analyze" is run. After some digging into the code we found that postgres potentially tries to open as many as a pre-determined maximum number of file descriptors when vacuuming. That number is the lesser of the one from the configuration file (max_files_per_process) and the one determined at start-up by "src/backend/storage/file/fd.c::count_usable_fds()". Under Solaris now, it would seem, finding out that number via dup(0) is not sufficient, as the actual number of interest might be/is the number of usable stream file descriptors (up until Solaris 10, at least). Also, closing the last recently used file descriptor might therefore not solve a temporary problem (as something below 256 is needed). Now, this can be fixed by setting/leaving the descriptor limit at 256 or changing the postgresql.conf setting accordingly. Still, the function for determining the max number is not working as intended under Solaris, it would appear. One might try using fopen() instead of dup() or have a different handling for stream and normal file descriptors (including moving standard file descriptors to above 255 to leave room for stream ones). Maybe though, all this is not worth the effort; then it might perhaps be a good idea to mention the limitations/specialties in the platform specific notes (e.g. have u/limit at 256 maximum).

cheers
hardy

Hartmut Raschick
Network Management Solutions
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KEYMILE GmbH
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