Re: [PATCH] Document that directly callable functions may use fn_extra

On 5/29/15 10:21 AM, Peter Eisentraut wrote:
> On 5/28/15 10:15 PM, Craig Ringer wrote:
>> I was a puzzled by src/backend/utils/fmgr/README and fmgr.h's
>> descriptions of fcinfo->flinfo->fn_extra (FmgrInfo.fn_extra) as they
>> seem to conflict with actual usage.
>>
>> The docs suggest that fl_extra is for the use of function call handlers,
>> but in practice it's also used heavily by function implementations as a
>> cache space.
>
> The documentation could also be updated about this. It mentions using
> fn_extra for PL handlers, gist functions, and set-returning functions,
> but it doesn't say that you can use it any old function for anything you
> want.
>
> I'm not sure how up to date that README actually is. It looks more like
> a historical document describing the original proposal.

FWIW, I think it'd be good to also document what lifetime you can expect
out of something in fn_extra. I realize you can figure it out from
fn_mcxt, but I don't know that that's terribly obvious to others.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Data in Trouble? Get it in Treble! http://BlueTreble.com