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111 lines
3.3 KiB
C
111 lines
3.3 KiB
C
/*
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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 perpose 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 datetime_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 "executor/spi.h" /* this is what you need to work with SPI */
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#include "commands/trigger.h" /* -"- and triggers */
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HeapTuple moddatetime(void);
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HeapTuple
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moddatetime()
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{
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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 (!CurrentTriggerData)
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elog(ERROR, "moddatetime: triggers are not initialized.");
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if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
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elog(ERROR, "moddatetime: can't process STATEMENT events.");
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if (TRIGGER_FIRED_AFTER(CurrentTriggerData->tg_event))
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elog(ERROR, "moddatetime: must be fired before event.");
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if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
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elog(ERROR, "moddatetime: must be fired before event.");
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else if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
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rettuple = CurrentTriggerData->tg_newtuple;
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else
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elog(ERROR, "moddatetime: can't process DELETE events.");
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rel = CurrentTriggerData->tg_relation;
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relname = SPI_getrelname(rel);
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trigger = CurrentTriggerData->tg_trigger;
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nargs = trigger->tgnargs;
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if (nargs != 1)
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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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/* Why do this? */
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CurrentTriggerData = NULL;
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/* Get the current datetime. */
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newdt = datetime_in("now");
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/*
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* This gets the position in the turple of the field we want. args[0]
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* being the name of the field to update, as passed in from the
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* 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 feild we are suppost 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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elog(ERROR, "moddatetime (%s): there is no attribute %s", relname,
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args[0]);
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/*
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* OK, this is where we make sure the datetime field that we are
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* modifying is really a datetime 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) != DATETIMEOID)
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elog(ERROR, "moddatetime (%s): attribute %s must be of DATETIME type",
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relname, args[0]);
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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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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 (rettuple);
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}
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