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* Getting field length in libpq
@ 1999-03-09 14:44 Bartek Teodorczyk <barteo@it.pl>
0 siblings, 1 reply; 2+ messages in thread
From: Bartek Teodorczyk @ 1999-03-09 14:44 UTC (permalink / raw)
To: pgsql-interfaces
I have following problem:
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?
BarTeo
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: [INTERFACES] Getting field length in libpq
@ 1999-03-09 15:08 Tom Lane <tgl@sss.pgh.pa.us>
parent: Bartek Teodorczyk <barteo@it.pl>
0 siblings, 0 replies; 2+ messages in thread
From: Tom Lane @ 1999-03-09 15:08 UTC (permalink / raw)
To: Bartek Teodorczyk <barteo@it.pl>; +Cc: pgsql-interfaces
Bartek Teodorczyk <barteo@it.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
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1999-03-09 14:44 Getting field length in libpq Bartek Teodorczyk <barteo@it.pl>
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