16.4. ��

src/test/regress/regress.c��contrib/spi�ˤϤ�ä�ʣ�����㤬����ޤ���

�ȥꥬ�λȤ����˴ؤ���ȤƤ��ñ����򤳤��˼����ޤ��� trigf �ؿ��ϡ��ȥꥬ��ȯ�Ԥ��� ttest ��졼�������ˤ��륿�ץ������𤷡��䤤��碌�� x �� NULL �ͤ��������褦�Ȥ��Ƥ������ϡ���������ȤФ��ޤ� (�Ĥޤꡢ���δؿ��ϡ��ȥ�󥶥����������Ǥ����ʤ� NOT NULL ����Τ褦��ư��򤷤ޤ�)��

#include "executor/spi.h" /* SPI  */
#include "commands/trigger.h"   /* -"- ����ӥȥꥬ����Ѥ������ɬ�פǤ� */

extern Datum trigf(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(trigf);

Datum
trigf(PG_FUNCTION_ARGS)
{
TriggerData    *trigdata = (TriggerData *) fcinfo->context;
    TupleDesc   tupdesc;
    HeapTuple   rettuple;
    char       *when;
    bool        checknull = false;
    bool        isnull;
    int         ret, i;

    /* trigdata �����Ԥɤ���Τ�Τ�ؤ��Ƥ��뤳�Ȥ��ǧ���ޤ� */
    if (!CALLED_AS_TRIGGER(fcinfo))
        elog(ERROR, "trigf:not fired by trigger manager");

    /* ���������塼�����֤����ץ� */
    if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
        rettuple = trigdata->tg_newtuple;
    else
        rettuple = trigdata->tg_trigtuple;

    /* NULL �ͤ�����å� */
    if (!TRIGGER_FIRED_BY_DELETE(trigdata->tg_event)
        && TRIGGER_FIRED_BEFORE(trigdata->tg_event))
        checknull = true;

    if (TRIGGER_FIRED_BEFORE(trigdata->tg_event))
        when = "before";
    else
        when = "after ";

    tupdesc = trigdata->tg_relation->rd_att;

    /* SPI�ޥ͡��������³���ޤ� */
    if ((ret = SPI_connect()) < 0)
        elog(INFO, "trigf (fired %s):SPI_connect returned %d", when, ret);

    /* ��졼�������Υ��ץ����������ޤ� */
    ret = SPI_exec("SELECT count(*) FROM ttest", 0);

    if (ret < 0)
        elog (NOTICE, "trigf (fired %s):SPI_exec returned %d", when, ret);

    /* PG7.2 �Ǥ� count(*) �� int8 ���֤��ޤ��� �Ѵ������դ��Ʋ�����*/
    i = (int) DatumGetInt64(SPI_getbinval(SPI_tuptable->vals[0],
                                          SPI_tuptable->tupdesc,
                                          1,
                                          &isnull));

    elog (NOTICE, "trigf (fired %s):there are %d tuples in ttest", when, i);

    SPI_finish();

    if (checknull)
    {
        (void) SPI_getbinval(rettuple, tupdesc, 1, &isnull);
        if (isnull)
            rettuple = NULL;
    }

    return PointerGetDatum(rettuple);
}

�����ǥ���ѥ����Ԥ����ȥꥬ�ؿ�����ޤ���

CREATE FUNCTION trigf () RETURNS TRIGGER AS
'...path_to_so' LANGUAGE C;

CREATE TABLE ttest (x int4);

vac=> CREATE TRIGGER tbefore BEFORE INSERT OR UPDATE OR DELETE ON ttest
FOR EACH ROW EXECUTE PROCEDURE trigf();
CREATE
vac=> CREATE TRIGGER tafter AFTER INSERT OR UPDATE OR DELETE ON ttest
FOR EACH ROW EXECUTE PROCEDURE trigf();
CREATE
vac=> INSERT INTO ttest VALUES (NULL);
WARNING:  trigf (fired before):there are 0 tuples in ttest
INSERT 0 0

-- �������ϤȤФ��졢�ޤ���AFTER�ȥꥬ��ȯ�Ԥ���ޤ���

vac=> SELECT * FROM ttest;
x
---
(0 rows)

vac=> INSERT INTO ttest VALUES (1);
INFO:  trigf (fired before):there are 0 tuples in ttest
INFO:  trigf (fired after ):there are 1 tuples in ttest
                                       ^^^^^^^^
                            �Ļ�����������פ��Ф��Ʋ�������
INSERT 167793 1
vac=> SELECT * FROM ttest;
x
---
 1
(1 row)

vac=> INSERT INTO ttest SELECT x * 2 FROM ttest;
INFO:  trigf (fired before):there are 1 tuples in ttest
INFO:  trigf (fired after ):there are 2 tuples in ttest
                                       ^^^^^^^^
                            �Ļ�����������פ��Ф��Ʋ�������
INSERT 167794 1
vac=> SELECT * FROM ttest;
x
---
 1
 2
(2 rows)

vac=> UPDATE ttest SET x = NULL WHERE x = 2;
INFO:  trigf (fired before):there are 2 tuples in ttest
UPDATE 0
vac=> UPDATE ttest SET x = 4 WHERE x = 2;
INFO:  trigf (fired before):there are 2 tuples in ttest
INFO:  trigf (fired after ):there are 2 tuples in ttest
UPDATE 1
vac=> SELECT * FROM ttest;
x
---
 1
 4
(2 rows)

vac=> DELETE FROM ttest;
INFO:  trigf (fired before):there are 2 tuples in ttest
INFO:  trigf (fired after ):there are 1 tuples in ttest
INFO:  trigf (fired before):there are 1 tuples in ttest
INFO:  trigf (fired after ):there are 0 tuples in ttest
                                       ^^^^^^^^
                            �Ļ�����������פ��Ф��Ʋ�������
DELETE 2
vac=> SELECT * FROM ttest;
x
---
(0 rows)