Re: pgsql: Add time/date macros for code clarity: #define

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Tom Lane wrote:
> >>> #define DAYS_PER_YEAR   365.25
> >>> #define MONTHS_PER_YEAR 12
> >>> #define DAYS_PER_MONTH  30
> >>> #define HOURS_PER_DAY   24
> >>
> >> Considering that only one of these four is actually an accurate
> >> constant, I have to question the usefulness of this.
>
> > Yea, the problem is that these non-absolute constants are littered all
> > through the code, so it is best to have them at least in one place.  I
> > will add a comment marking the non-accurate ones more clearly.
>
> Unless you comment every single use of the macros, you won't have
> addressed my point.  No one will ever read "DAYS_PER_YEAR" in the midst
> of some code and not stop to wonder "hmm, is that 365, or 365.25, or
> 365.2425"?  And in most places where this might be used, that's not
> an ignorable issue.  I think it is actually better to write out the
> literal number, because then you can see right away what is happening.
>
> In short, I don't think this is an improvement.

The problem is that 24 or 30 or 60 doesn't really say what it is, while
the macros are self-documenting.  The 30 is aparticular problem because
I am like, hey, what does that 30 mean, then I have to think about it.
What we can do is to rename them to AVG_* macros so it is clear it is
approximate.

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