Re: Selecting a constant question

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От Tom Lane
Тема Re: Selecting a constant question
Дата
Msg-id 21188.1181593946@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: Selecting a constant question  ("Dann Corbit" <DCorbit@connx.com>)
Ответы Re: Selecting a constant question  ("Dann Corbit" <DCorbit@connx.com>)
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"Dann Corbit" <DCorbit@connx.com> writes:
> The issue is this:
> Postgres describes the column with a typmod of -1 (unknown) and a length
> of 65534.

Oh, you're looking at typlen not typmod.  Please observe the comments in
pg_type.h:
/* * For a fixed-size type, typlen is the number of bytes we use to * represent a value of this type, e.g. 4 for an
int4.   But for a * variable-length type, typlen is negative.  We use -1 to indicate a * "varlena" type (one that has a
lengthword), -2 to indicate a * null-terminated C string. */int2        typlen;
 

You should be treating typlen as signed not unsigned, and not assuming a
fixed width for any negative value.

Since the width refers to the server internal representation, and not to
what comes down the wire, I find it pretty strange for an application to
be using typlen for anything at all actually.
        regards, tom lane


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