PostgreSQL used fsync incorrectly for 20 years

Re:PostgreSQL used fsync incorrectly for 20 years by garganzol on Sunday February 10, 2019 @05:27AM (#19127204)

That's an excellent patch. Partial writes (and reads) is a known behavior which is often overlooked. It rarely (if ever) occurs on local file systems, and even the network ones manifest it only from time to time, usually when there is some kind of congestion/segmentation is going on.

It's a pity a lot developers out there do not have an ingrained awareness about this.

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Re:PostgreSQL used fsync incorrectly for 20 years by jeffdavis on Sunday February 10, 2019 @11:31AM (#19128410)

Everyone in that thread knows what a partial write is. That's why the patch author saw this error message:

    > 2011-07-31 22:13:35 EST postgres postgres [local] LOG: connection authorized: user=postgres database=postgres
    > 2011-07-31 22:13:35 EST ERROR: could not write block 1 of relation global/2671: wrote only 4096 of 8192 bytes
    > 2011-07-31 22:13:35 EST HINT: Check free disk space.
    > 2011-07-31 22:13:35 EST CONTEXT: writing block 1 of relation global/2671
    > 2011-07-31 22:13:35 EST [unknown] [unknown] LOG: connection received: host=[local]

If they didn't know what a partial write was, they wouldn't have identified it specifically as an error case with its own informative error message.

The proposed patch retries rather than throwing an error.

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