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Diffstat (limited to 'contrib/spi/moddatetime.c')
| -rw-r--r-- | contrib/spi/moddatetime.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/contrib/spi/moddatetime.c b/contrib/spi/moddatetime.c new file mode 100644 index 0000000..3eb7004 --- /dev/null +++ b/contrib/spi/moddatetime.c @@ -0,0 +1,130 @@ +/* +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); +} |