Date: Wed, 26 Mar 2003 17:47:11 -0500
From: "G. Anthony Reina" <gar8+@pitt.edu>
Subject: Re: How can I pass an array from PostgreSQL to C (libpq)?
In-reply-to: <3E81FA6A.8090201@joeconway.com>
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To: Joe Conway <mail@joeconway.com>
Cc: pgsql-sql@postgresql.org
Message-id: <519653832.1048700831@dell1.neurobio.pitt.edu>
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References: <3E81FA6A.8090201@joeconway.com>

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@joeconway.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
>