On Sat, Jul 30, 2016 at 2:47 AM, David G. Johnston <david.g.johns...@gmail.com> wrote: > After bouncing on this for a bit I'm inclined to mark the bug itself "won't > fix" but introduce a "to_binary_iso" function (I'm hopeful a better name > will emerge...) that will output a number using ISO binary suffixes. I > would document this under 9.8 "data type formatting functions" instead of > within system functions.
I think Bruce's summary is a bit revisionist. All these standards are attempts to reconcile two different conflicting traditions that have been conflicting for decades. There's a conflict for a reason though and the tradition of using powers of 2 is well-ingrained in plenty of practices and software, not just Postgres. Personally I'm pretty satisfied with the current mode of operation because I think powers of 2 are vastly more useful and more likely to be what the user actually wants. You would be hard pressed to find any users actually typing KiB or MiB in config files and being surprised they don't work or any users typing work_mem=100MB and being surprised that they're not getting 95.367 MiB. If you really want to support a strict interpretation of the SI standards then I don't see anything wrong with having a GUC. It doesn't change the semantics of SQL parsing so the worst-case downside is that if you change the setting and then reload a config file or if you move a setting from one place in a config file to another the interpretation of the config file would change. The best practice would probably be to set this config at the top of the config file and nowhere else. I would suggest having a GUC like "strict_si_units" with false as the default. If it's true then units like KiB and KB are both accepted and mean different things. If it's false then still accept both but treat them as synonyms meaning powers of 2. This means users who don't care can continue using convenient powers of 2 everywhere without thinking about it and users who do can start using the new-fangled SI units (and have the pitfall of accidentally specifying in units of powers of 10). For outputs like pg_size_pretty, SHOW, and pg_settings you could either say to always use KiB so that the outputs are always correct to use regardless of the setting of strict_si_units or you could have it print KB et al when strict_si_units is false -- the latter have the advantage that outputs could be copied to older versions safely but the disadvantage that if you change the setting then the interpretation of existing config files change. I think it would be better to print KiB/MiB etc always. I suppose there's the alternative of trying to guess which unit results in the most concise display but that seems unnecessarily baroque and likely to just hide mistakes rather than help. -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
