Re: [INTERFACES] Getting field length in libpq

Bartek Teodorczyk <barteo(at)it(dot)pl> writes:
> I need to get the length of field after executing query. For INT4 fields
> it is simple (call PQfsize and get 4) but when I have VARCHAR(30) field
> PQfsize returns -1. I cannot call PQgetlength for example first tuple
> because this tuple can have 10 chars and PQgetlength returns 10 but I
> need 30. Have you any solutions?

I believe PQfmod will give you the number you want, for the specific
case of char and varchar fields. The meaning of PQfmod is by definition
type-specific, so there's no guarantee that it will contain the maximum
field width for other data types. For that matter, there's no guarantee
that a VARLENA data type even *has* an identifiable maximum width ---
the handiest example of one that does not is text.

If I were you I'd check PQftype before assuming that I knew what PQfmod
means.

BTW, keep in mind that PQfsize is the stored size of a datum, but unless
you are using binary cursors it has nothing to do with the length of the
ASCII representation of the value...

regards, tom lane