# 47.6. Examples
This section contains a very simple example of SPI usage. The C function execq
takes an SQL command as its first argument and a row count as its second, executes the command using SPI_exec
and returns the number of rows that were processed by the command. You can find more complex examples for SPI in the source tree in src/test/regress/regress.c
and in the spi module.
#include "postgres.h"
#include "executor/spi.h"
#include "utils/builtins.h"
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(execq);
Datum
execq(PG_FUNCTION_ARGS)
{
char *command;
int cnt;
int ret;
uint64 proc;
/* Convert given text object to a C string */
command = text_to_cstring(PG_GETARG_TEXT_PP(0));
cnt = PG_GETARG_INT32(1);
SPI_connect();
ret = SPI_exec(command, cnt);
proc = SPI_processed;
/*
* If some rows were fetched, print them via elog(INFO).
*/
if (ret > 0 && SPI_tuptable != NULL)
{
SPITupleTable *tuptable = SPI_tuptable;
TupleDesc tupdesc = tuptable->tupdesc;
char buf[8192];
uint64 j;
for (j = 0; j < tuptable->numvals; j++)
{
HeapTuple tuple = tuptable->vals[j];
int i;
for (i = 1, buf[0] = 0; i <= tupdesc->natts; i++)
snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), " %s%s",
SPI_getvalue(tuple, tupdesc, i),
(i == tupdesc->natts) ? " " : " |");
elog(INFO, "EXECQ: %s", buf);
}
}
SPI_finish();
pfree(command);
PG_RETURN_INT64(proc);
}
This is how you declare the function after having compiled it into a shared library (details are in Section 38.10.5.):
CREATE FUNCTION execq(text, integer) RETURNS int8
AS 'filename'
LANGUAGE C STRICT;
Here is a sample session:
=> SELECT execq('CREATE TABLE a (x integer)', 0);
execq