Re: wal_sync_method as enum

Magnus Hagander wrote:
> Attached patch implements wal_sync_method as an enum. I'd like someone
> to look it over before I apply it - I don't have the machines to test
> all codepaths (and some of it is hard to test - better to read it and
> make sure it's right).
>
> In order to implement the enum guc, I had to break out a new
> SYNC_METHOD_OPEN_DSYNC out of SYNC_METHOD_OPEN where it was previously
> overloaded. This is one of the parts where I'm slightly worried I have
> made a mistake.

I took a look at this and I like it -- it seems correct as far as I can
tell, and it has the nice property that we can display the list of
values that the current platform actually support.

This thing looked a bit dubious to me at first:

> !     switch (new_sync_method)
>       {
> !         case SYNC_METHOD_FSYNC:
> !         case SYNC_METHOD_FSYNC_WRITETHROUGH:
> !         case SYNC_METHOD_FDATASYNC:

because at least some of the values are only present on some platforms.
However, I think realized that the actual values are present on all
platforms, independent of whether they represent a supported fsync
method, so this is OK.  Perhaps it would be good to add a comment on top
of the switch statement explaining this.  Otherwise looks fine.

Well, and the ereport("FIXME") needs to be improved :-)

--
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.