Re: How can I pass an array from PostgreSQL to C (libpq)?

On Wed, 26 Mar 2003, G. Anthony Reina wrote:

See contrib/intarray

> Yes, in the past I had used binary cursor and things seemed to work fine.
> However, recently when I ran the binary cursor stuff, the array ends up
> getting shifted to the right one index. So what should be placed in
> array_var[n] was getting placed in array var[n+1]. Plus, I was always a
> little concerned with the binary cursor when going across platforms (e.g.
> endianess, alignment).
>
> I ended up just writing a little script that parses the string for the
> comma separators. That works fine, but wanted to see if others had more
> elegant solutions. I'll take a look at the /utils directory you mentioned.
> Perhaps there are functions that I'm not aware of (e.g. I didn't know there
> was a built in function called array_dims that gives the array dimensions).
>
> -Tony
>
>
> --On Wednesday, March 26, 2003 11:07 AM -0800 Joe Conway
> <mail(at)joeconway(dot)com> wrote:r
> >
> > PQgetvalue is always going to give you the string representation of the
> > field value *unless* you specify a binary cursor. In that case you'll get
> > all requested fields in binary form, and it's your responsibility to deal
> > with making sense of what you get. There are some backend macros and
> > functions that can help you get at array values. Take a look at
> > src/utils/adt/arrayfuncs.c and src/include/utils/array.h. You might want
> > to read through contrib/array and/or contrib/intarray for examples.
> >
> > You could also consider writing your array manipulation code in a user
> > defined C function and just return the end result to the libpq program.
> > It's hard to know if this is an option without more detail on what you're
> > trying to do.
> >
> > Joe
> >
>
>
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