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