Re: custom function for converting human readable sizes to bytes

Hi

new update:

1. unit searching is case insensitive

2. initial support for binary byte prefixes - KiB, MiB, .. (IEC standard),
change behave for SI units

Second point is much more complex then it is looking - if pg_size_bytes
should be consistent with pg_size_pretty.

The current pg_size_pretty and transformations in guc.c are based on JEDEC
standard. Using this standard for GUC has sense - using it for object sizes
is probably unhappy.

I tried to fix (and enhance) pg_size_pretty - now reports correct units,
and via second parameter it allows to specify base: 2 (binary, IEC -
default) or 10 (SI).

I think it is good to have it. These standards are generic and wide used,
but should to be pretty explained in documentation if we will use JEDEC for
configuration. Probably better to leave JEDEC and prefer SI and IEC.

Plan B is fix Postgres on JEDEC only - it is trivial, simple - but it can
look like archaic in next years.

Comments, notices?

Regards

Pavel