Re: custom function for converting human readable sizes to bytes

On Tue, Dec 22, 2015 at 10:45 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
wrote:

> Hi
>
> 2015-12-21 16:11 GMT+01:00 Robert Haas <robertmhaas(at)gmail(dot)com>:
>
>> On Sun, Dec 20, 2015 at 4:54 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
>> wrote:
>> > 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).
>>
>> -1 from me. I don't think we should muck with the way pg_size_pretty
>> works.
>>
>
> new update - I reverted changes in pg_size_pretty
>

Hi,

I didn't check out earlier versions of this patch, but the latest one still
changes pg_size_pretty() to emit PB suffix.

I don't think it is worth it to throw a number of changes together like
that. We should focus on adding pg_size_bytes() first and make it
compatible with both pg_size_pretty() and existing GUC units: that is
support suffixes up to TB and make sure they have the meaning of powers of
2^10, not 10^3. Re-using the table present in guc.c would be a plus.

Next, we could think about adding handling of PB suffix on input and
output, but I don't see a big problem if that is emitted as 1024TB or the
user has to specify it as 1024TB in a GUC or argument to pg_size_bytes():
an minor inconvenience only.

--
Alex