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Viewing changes to contrib/spi/moddatetime.c

  • Committer: Bazaar Package Importer
  • Author(s): Martin Pitt
  • Date: 2009-03-20 12:00:13 UTC
  • Revision ID: james.westby@ubuntu.com-20090320120013-hogj7egc5mjncc5g
Tags: upstream-8.4~0cvs20090328
Import upstream version 8.4~0cvs20090328

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contrib/spi/moddatetime.c
 
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/*
 
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moddatetime.c
 
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$PostgreSQL$
 
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What is this?
 
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It is a function to be called from a trigger for the purpose of updating
 
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a modification datetime stamp in a record when that record is UPDATEd.
 
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Credits
 
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This is 95%+ based on autoinc.c, which I used as a starting point as I do
 
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not really know what I am doing.  I also had help from
 
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Jan Wieck <jwieck@debis.com> who told me about the timestamp_in("now") function.
 
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OH, me, I'm Terry Mackintosh <terry@terrym.com>
 
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*/
 
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#include "postgres.h"
 
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#include "catalog/pg_type.h"
 
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#include "executor/spi.h"
 
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#include "commands/trigger.h"
 
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PG_MODULE_MAGIC;
 
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extern Datum moddatetime(PG_FUNCTION_ARGS);
 
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PG_FUNCTION_INFO_V1(moddatetime);
 
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Datum
 
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moddatetime(PG_FUNCTION_ARGS)
 
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{
 
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        TriggerData *trigdata = (TriggerData *) fcinfo->context;
 
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        Trigger    *trigger;            /* to get trigger name */
 
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        int                     nargs;                  /* # of arguments */
 
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        int                     attnum;                 /* positional number of field to change */
 
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        Datum           newdt;                  /* The current datetime. */
 
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        char      **args;                       /* arguments */
 
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        char       *relname;            /* triggered relation name */
 
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        Relation        rel;                    /* triggered relation */
 
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        HeapTuple       rettuple = NULL;
 
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        TupleDesc       tupdesc;                /* tuple description */
 
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        if (!CALLED_AS_TRIGGER(fcinfo))
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime: not fired by trigger manager");
 
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        if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime: cannot process STATEMENT events");
 
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        if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime: must be fired before event");
 
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        if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime: must be fired before event");
 
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        else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
 
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                rettuple = trigdata->tg_newtuple;
 
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        else
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime: cannot process DELETE events");
 
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        rel = trigdata->tg_relation;
 
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        relname = SPI_getrelname(rel);
 
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        trigger = trigdata->tg_trigger;
 
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        nargs = trigger->tgnargs;
 
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        if (nargs != 1)
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime (%s): A single argument was expected", relname);
 
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        args = trigger->tgargs;
 
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        /* must be the field layout? */
 
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        tupdesc = rel->rd_att;
 
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        /* Get the current datetime. */
 
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        newdt = DirectFunctionCall3(timestamp_in,
 
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                                                                CStringGetDatum("now"),
 
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                                                                ObjectIdGetDatum(InvalidOid),
 
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                                                                Int32GetDatum(-1));
 
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        /*
 
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         * This gets the position in the tuple of the field we want. args[0] being
 
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         * the name of the field to update, as passed in from the trigger.
 
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         */
 
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        attnum = SPI_fnumber(tupdesc, args[0]);
 
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        /*
 
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         * This is were we check to see if the field we are supposed to update
 
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         * even exits.  The above function must return -1 if name not found?
 
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         */
 
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        if (attnum < 0)
 
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                ereport(ERROR,
 
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                                (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
 
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                                 errmsg("\"%s\" has no attribute \"%s\"",
 
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                                                relname, args[0])));
 
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        /*
 
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         * OK, this is where we make sure the timestamp field that we are
 
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         * modifying is really a timestamp field. Hay, error checking, what a
 
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         * novel idea !-)
 
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         */
 
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        if (SPI_gettypeid(tupdesc, attnum) != TIMESTAMPOID)
 
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                ereport(ERROR,
 
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                                (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
 
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                                 errmsg("attribute \"%s\" of \"%s\" must be type TIMESTAMP",
 
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                                                args[0], relname)));
 
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/* 1 is the number of items in the arrays attnum and newdt.
 
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        attnum is the positional number of the field to be updated.
 
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        newdt is the new datetime stamp.
 
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        NOTE that attnum and newdt are not arrays, but then a 1 ellement array
 
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        is not an array any more then they are.  Thus, they can be considered a
 
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        one element array.
 
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*/
 
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        rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, &newdt, NULL);
 
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        if (rettuple == NULL)
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime (%s): %d returned by SPI_modifytuple",
 
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                         relname, SPI_result);
 
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/* Clean up */
 
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        pfree(relname);
 
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        return PointerGetDatum(rettuple);
 
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}