2009/10/26 ChenXun <p.smasher@hotmail.com>:
> Hello,
>
> I'm starting to learn programming with libpq.
> In the main loop of my code, I will receive some data in the format of an
> array of a struct. The data will be inserted to the database, in different
> lines.
> I also need to update the last record in the table before the insertion. So
> I plan to write a pl/pgsql function (procedure) to perform the whole
> updating and inserting.
> But I don't know how to pass the array to the procedure through libpq. It
> seems the only way is to using libpq to do updating and inserting
> separately. Like this
>
> for(;;) {
> /* receive data */
>
> /* libpq updating */
> PQexec(...);
>
> PQprepare(...);
> for (i=0; i<n; i++) {
> /* libpq inserting */
> PQexecPrepared()...
> }
> }
>
> The PQprepare function has to be called in each loop.So my question is that
> whether there is a method to pass the array as parameter to libpq?
check out libpqtypes (http://libpqtypes.esilo.com/). It's exactly what
you want. We expose sending arrays/composites directly in
paramaterized fashion in binary (no escaping). You still have to loop
because a C array is not directly compatible to postgres array.
PGint4 i;
PGarray arr;
PGparam *param;
arr.ndims = 0;
arr.param = PQparamCreate(conn);
for(i=0; i < 1000; i++)
PQputf(arr.param, "%int4", i); // client side
param = PQparamCreate(conn);
PQputf(param, "%int[]", &arr); // client side
res = PQparamExec(conn, param, "insert into foo values ($1)", 0);
merlin
