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);
}
</programlisting>

  <para>
   This is how you declare the function after having compiled it into
   a shared library (details are in <xref linkend="dfunc"/>.):

<programlisting>
CREATE FUNCTION execq(text, integer) RETURNS int8
    AS '<replaceable>filename</replaceable>'
    LANGUAGE C STRICT;
</programlisting>
  </para>

  <para>
   Here is a sample session:

<programlisting>
=&gt; SELECT execq('CREATE TABLE a (x integer)', 0);
 execq
-------
     0
(1 row)

=&gt; INSERT INTO a VALUES (execq('INSERT INTO a VALUES (0)', 0));
INSERT 0 1
=&gt; SELECT execq('SELECT * FROM a', 0);
INFO:  EXECQ:  0    <lineannotation>-- inserted by execq</lineannotation>
INFO:  EXECQ:  1    <lineannotation>-- returned by execq and inserted by upper INSERT</lineannotation>

 execq
-------
     2
(1 row)

=&gt; SELECT execq('INSERT INTO a SELECT x + 2 FROM a RETURNING *', 1);
INFO:  EXECQ:  2    <lineannotation>-- 0 + 2, then execution was stopped by count</lineannotation>
 execq
-------
     1
(1 row)

=&gt; SELECT execq('SELECT * FROM a', 10);
INFO:  EXECQ:  0
INFO:  EXECQ:  1
INFO:  EXECQ:  2

 execq
-------
     3              <lineannotation>-- 10 is the max value only, 3 is the real number of rows</lineannotation>
(1 row)

=&gt; SELECT execq('INSERT INTO a SELECT x + 10 FROM a', 1);
 execq
-------
     3              <lineannotation>-- all rows processed; count does not stop it, because nothing is returned</lineannotation>
(1 row)

=&gt; SELECT * FROM a;
 x
----
  0
  1
  2
 10
 11
 12
(6 rows)

=&gt; DELETE FROM a;
DELETE 6
=&gt; INSERT INTO a VALUES (execq('SELECT * FROM a', 0) + 1);
INSERT 0 1
=&gt; SELECT * FROM a;
 x
---
 1                  <lineannotation>-- 0 (no rows in a) + 1</lineannotation>
(1 row)

=&gt; INSERT INTO a VALUES (execq('SELECT * FROM a', 0) + 1);
INFO:  EXECQ:  1
INSERT 0 1
=&gt; SELECT * FROM a;
 x
---
 1
 2                  <lineannotation>-- 1 (there was one row in a) + 1</lineannotation>
(2 rows)

<lineannotation>-- This demonstrates the data changes visibility rule.</lineannotation>
<lineannotation>-- execq is called twice and sees different numbers of rows each time:</lineannotation>

=&gt; INSERT INTO a SELECT execq('SELECT * FROM a', 0) * x FROM a;
INFO:  EXECQ:  1    <lineannotation>-- results from first execq</lineannotation>
INFO:  EXECQ:  2
INFO:  EXECQ:  1    <lineannotation>-- results from second execq</lineannotation>
INFO:  EXECQ:  2
INFO:  EXECQ:  2
INSERT 0 2
=&gt; SELECT * FROM a;
 x
---
 1
 2
 2                  <lineannotation>-- 2 rows * 1 (x in first row)</lineannotation>
 6                  <lineannotation>-- 3 rows (2 + 1 just inserted) * 2 (x in second row)</lineannotation>
(4 rows)
</programlisting>
  </para>
 </sect1>
</chapter>