PostgreSQL Discussion - Help with SPI...

Author

Help with SPI...

Cristian Prieto

2005-08-30, 8:24 pm

Hi, I will try to explain the most possible my question:

I'm writing a Store Procedure as a C Language Function in the Database, I need to handle a bytea (binary objetc) and store it in a modified mode in the database, I've done it in the following way:

PG_FUNCTION_INFO_V1(
myspi);

Datum
myspi(PG_FUNCTION_AR
GS)
{
int ret;
bool isnull;
bytea *val;

ret = SPI_connect();

ret = SPI_exec("SELECT val FROM binary_table", 1);
if (ret == SPI_OK_SELECT && SPI_processed > 0) {
TupleDesc tupdesc = SPI_tuptable->tupdesc;
SPITupleTable *tuptable = SPI_tuptable;

val = DatumGetByteP(SPI_ge
tbinval(tuptable->vals[0], tupdesc, 1, &isnull));
}

/* Here I use and modified the new version of the val value */

// I don't know what to do here to store the new value again :(

SPI_finish();
PG_RETURN_INT32(val)
;
}

Well, the new value is really the content of a memory segment, I know I could store it again using SPI and an UPDATE statement, but that means that I need to transform the val value into a string, and I don't know the length of the string with the scape characters added.

Any idea in how to handle this?

Thanks a lot...

Michael Fuhr

2005-08-31, 3:24 am

On Tue, Aug 30, 2005 at 01:28:11PM -0600, Cristian Prieto wrote:
> Well, the new value is really the content of a memory segment, I
> know I could store it again using SPI and an UPDATE statement, but
> that means that I need to transform the val value into a string,
> and I don't know the length of the string with the scape characters
> added.

You could use SPI_prepare() and SPI_execp() without having to
transform the bytea value into a string; see the SPI documentation
and look around for examples that use numbered parameters ($1, $2,
etc.).

--
Michael Fuhr

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