Re: Converting postgresql.conf parameters to kilobytes

On Tuesday 01 June 2004 14:12, Shridhar Daithankar wrote:
> Actually I need to find out few more things about it. It is not as simple
> as adding a assign_hook. When I tried to initdb with changes, it demanded
> 64MB of shared buffers which I (now) think that somewhere NBuffers are used
> before postgresql.conf is parsed. So 8192*8000=64MB. But this is just
> guesswork. Haven't looked in it there.

Found it. Following is the code that is causing problem.

guc.c:2998
-----------
if (conf->assign_hook)
if (!(*conf->assign_hook) (newval, changeVal, source))
{
ereport(elevel,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid value for parameter \"%s\": %d",
name, newval)));
return false;
}

if (changeVal || makeDefault)
{
if (changeVal)
{
*conf->variable = newval;
conf->gen.source = source;
}
-----------

So even if assign_hook is executed, the value of variable is overwritten in
next step which nullifies any factoring/change in value done in assign hook.

I find this as a convention at many other place at guc.c. Call assign_hook and
the overwrite the value. So is assign_hook called only to validate the value?
How do I modify the value of the variable without getting specific?

I tried

if (changeVal && !(conf->assign_hook))

and it worked. However that is just for int variables. I am not sure if that
is a design decision. What should I do?

Regards,
Shridhar