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List:       postgresql-general
Subject:    Re: [GENERAL] Importing data w/ Unix timestamp
From:       Tom Lane <tgl () sss ! pgh ! pa ! us>
Date:       2000-06-29 19:04:01
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Thomas Lockhart <lockhart@alumni.caltech.edu> writes:
> Another side comment: afaik an explicit conversion to abstime is not
> required to go from Unix time to timestamp. So
>   insert into RealTable select uname, timestamp(timeinAsInt4),
>                                duration, etc from TempTable;
> should be equivalent.

Ah, right, that does work.  Just to drift a little further off topic,
the locutions
		timeinAsInt4::timestamp
		cast (timeinAsInt4 as timestamp)
do not work, because in those cases the parser expects to find a
one-step conversion method, and there isn't one --- at least not in
the standard set of Postgres functions.  The function-call syntax works
because there is a function timestamp(abstime) and the parser figures
out it can resolve the ambiguous function name timestamp() as that
function if it first applies int4-to-abstime coercion, which it knows
how to do.

In short: you can get a two-step type conversion from the function call
notation, but only one-step from cast notation.

			regards, tom lane

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