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/*
moddatetime.c
contrib/spi/moddatetime.c
What is this?
It is a function to be called from a trigger for the purpose 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 "postgres.h"
#include "access/htup_details.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "executor/spi.h"
#include "utils/builtins.h"
#include "utils/rel.h"
PG_MODULE_MAGIC;
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 */
Oid atttypid; /* type OID of field to change */
Datum newdt; /* The current datetime. */
bool newdtnull; /* null flag for it */
char **args; /* arguments */
char *relname; /* triggered relation name */
Relation rel; /* triggered relation */
HeapTuple rettuple = NULL;
TupleDesc tupdesc; /* tuple description */
if (!CALLED_AS_TRIGGER(fcinfo))
/* internal error */
elog(ERROR, "moddatetime: not fired by trigger manager");
if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
/* internal error */
elog(ERROR, "moddatetime: must be fired for row");
if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
/* internal error */
elog(ERROR, "moddatetime: must be fired before event");
if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
/* internal error */
elog(ERROR, "moddatetime: cannot process INSERT events");
else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
rettuple = trigdata->tg_newtuple;
else
/* internal error */
elog(ERROR, "moddatetime: cannot process DELETE events");
rel = trigdata->tg_relation;
relname = SPI_getrelname(rel);
trigger = trigdata->tg_trigger;
nargs = trigger->tgnargs;
if (nargs != 1)
/* internal error */
elog(ERROR, "moddatetime (%s): A single argument was expected", relname);
args = trigger->tgargs;
/* must be the field layout? */
tupdesc = rel->rd_att;
/*
* This gets the position in the tuple 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 where we check to see if the field we are supposed to update
* even exists.
*/
if (attnum <= 0)
ereport(ERROR,
(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
errmsg("\"%s\" has no attribute \"%s\"",
relname, args[0])));
/*
* Check the target field has an allowed type, and get the current
* datetime as a value of that type.
*/
atttypid = SPI_gettypeid(tupdesc, attnum);
if (atttypid == TIMESTAMPOID)
newdt = DirectFunctionCall3(timestamp_in,
CStringGetDatum("now"),
ObjectIdGetDatum(InvalidOid),
Int32GetDatum(-1));
else if (atttypid == TIMESTAMPTZOID)
newdt = DirectFunctionCall3(timestamptz_in,
CStringGetDatum("now"),
ObjectIdGetDatum(InvalidOid),
Int32GetDatum(-1));
else
{
ereport(ERROR,
(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
errmsg("attribute \"%s\" of \"%s\" must be type TIMESTAMP or TIMESTAMPTZ",
args[0], relname)));
newdt = (Datum) 0; /* keep compiler quiet */
}
newdtnull = false;
/* Replace the attnum'th column with newdt */
rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc,
1, &attnum, &newdt, &newdtnull);
/* Clean up */
pfree(relname);
return PointerGetDatum(rettuple);
}
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