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Trigger performance

From: pginfo <pginfo(at)t1(dot)unisoftbg(dot)com>
To: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Trigger performance
Date: 2004-01-22 09:35:17
Message-ID: 400F9955.3C0FD784@t1.unisoftbg.com (view raw or flat)
Thread:
Lists: pgsql-performance
Hi,

I need to speed up the triggers that we are using and I began to make
some tests to compare the "C" and pgSQL trigger performance.

I try to write two identical test triggers (sorry I do not know very
good the pgsql C interface and I got one of examples and werite it) and
attached it on insert of my test table.

After it I try to insert in thi stable ~ 160 K rows and compared the
speeds.

I was supprised that the pgsql trigger take ~8 sec. to insert this rows
and the "C" trigger take ~ 17 sec.

This are my triggers:
CREATE OR REPLACE FUNCTION trig1_t()
  RETURNS trigger AS
'
DECLARE

my_rec RECORD;

BEGIN

select into my_rec count(*) from ttest;

RETURN NEW;
END;
'
  LANGUAGE 'plpgsql' VOLATILE;

and this writen in "C":

#include "postgres.h"
 #include "executor/spi.h"       /* this is what you need to work with
SPI */
 #include "commands/trigger.h"   /* ... and triggers */

 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;

     /* make sure it's called as a trigger at all */
     if (!CALLED_AS_TRIGGER(fcinfo))
         elog(ERROR, "trigf: not called by trigger manager");

     /* tuple to return to executor */
     if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
         rettuple = trigdata->tg_newtuple;
     else
         rettuple = trigdata->tg_trigtuple;

     /* check for null values */
     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;

     /* connect to SPI manager */
     if ((ret = SPI_connect()) < 0)
         elog(INFO, "trigf (fired %s): SPI_connect returned %d", when,
ret);

     /* get number of rows in table */
     ret = SPI_exec("SELECT count(*) FROM ttest", 0);

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


     SPI_finish();

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

     return PointerGetDatum(rettuple);
 }



My question:
Can I do the "C" trigger to be faster that the pgSQL?

regards,
ivan.



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