On Aug 28, 2007, at 17:22 , D. Dante Lorenso wrote:
Michael Glaesemann wrote:
On Aug 28, 2007, at 16:55 , D. Dante Lorenso wrote:
RETURN time + (days || ' days')::INTERVAL;
It's bad practice to concatenate like this. Use time + days *
interval '1 day' and be done with it.
Why? Is this functionality expected to break in the future or has
unexpected side effects? Is it less clear or less efficient? Who
declared it bad practice and where can I read that documentation?
It's generally bad practice to interpolate unnecessarily. You're
right, in this case you're probably safe from this particular case
ever changing. I personally find it less clear (though clarity is
often in the eye of the beholder). time + * interval '1 day' is to
me a clearer expression of what you're doing: add this multiple of
days to the time.
(days || ' days')::interval says "Make a string using this value (oh,
it's an int? we need to cast it to text) and this string: the result
just happens to match the proper input format for an interval, which
is fortunate because now we're casting the string to interval". Okay,
there's a little editorializing thrown in, but that's what the
concatenation says to me.
The concatenation is probably less efficient: you're casting an int
to text and then the text to interval with the concatenation you're
using. I don't know how that compares in terms of cycles to the int *
interval math, but efficiency isn't really the reason I would avoid it.
I'm sure others could provide more cogent explanations, but those are
my initial thoughts.
Michael Glaesemann
grzm seespotcode net
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