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  • Committer: Package Import Robot
  • Author(s): Martin Pitt
  • Date: 2013-05-08 05:39:52 UTC
  • Revision ID: package-import@ubuntu.com-20130508053952-1j7uilp7mjtrvq8q
Tags: upstream-9.3~beta1
Import upstream version 9.3~beta1

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contrib/spi/moddatetime.c
 
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/*
 
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moddatetime.c
 
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contrib/spi/moddatetime.c
 
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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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#include "utils/rel.h"
 
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#include "utils/timestamp.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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        Oid                     atttypid;               /* type OID 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_ROW(trigdata->tg_event))
 
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                /* internal error */
 
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                elog(ERROR, "moddatetime: must be fired for row");
 
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        if (!TRIGGER_FIRED_BEFORE(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: cannot process INSERT events");
 
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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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        /*
 
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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 where we check to see if the field we are supposed to update
 
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         * even exists. 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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         * Check the target field has an allowed type, and get the current
 
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         * datetime as a value of that type.
 
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         */
 
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        atttypid = SPI_gettypeid(tupdesc, attnum);
 
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        if (atttypid == TIMESTAMPOID)
 
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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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        else if (atttypid == TIMESTAMPTZOID)
 
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                newdt = DirectFunctionCall3(timestamptz_in,
 
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                                                                        CStringGetDatum("now"),
 
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                                                                        ObjectIdGetDatum(InvalidOid),
 
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                                                                        Int32GetDatum(-1));
 
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        else
 
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        {
 
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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 or TIMESTAMPTZ",
 
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                                                args[0], relname)));
 
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                newdt = (Datum) 0;              /* keep compiler quiet */
 
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        }
 
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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 element 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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}