Re: Allowing WAL fsync to be done via O_SYNC

Tom Lane writes:

> I think we need to make both O_SYNC and fsync() choices available in
> 7.1. Two important questions need to be settled:
>
> 1. Is a compile-time flag (in config.h.in) good enough, or do we need
> to make it configurable via a GUC variable? (A variable would have to
> be postmaster-start-time changeable only, so you'd still need a
> postmaster restart to change it.)

As a general rule, if something can be a run time option, as opposed to a
compile time option, then it should be. At the very least you keep the
installation simple and allow for easier experimenting.

> There's also the lesser question of what to call the config symbol
> or variable.

I suggest "wal_use_fsync" as a GUC variable, assuming the default would be
off. Otherwise "wal_use_open_sync". (Use a general-to-specific naming
scheme to allow for easier grouping. Having defaults be "off"
consistently is more intuitive.)

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/