1 /* 2 moddatetime.c 3 4 contrib/spi/moddatetime.c 5 6 What is this? 7 It is a function to be called from a trigger for the purpose of updating 8 a modification datetime stamp in a record when that record is UPDATEd. 9 10 Credits 11 This is 95%+ based on autoinc.c, which I used as a starting point as I do 12 not really know what I am doing. I also had help from 13 Jan Wieck <jwieck@debis.com> who told me about the timestamp_in("now") function. 14 OH, me, I'm Terry Mackintosh <terry@terrym.com> 15 */ 16 #include "postgres.h" 17 18 #include "access/htup_details.h" 19 #include "catalog/pg_type.h" 20 #include "executor/spi.h" 21 #include "commands/trigger.h" 22 #include "utils/builtins.h" 23 #include "utils/rel.h" 24 25 PG_MODULE_MAGIC; 26 27 PG_FUNCTION_INFO_V1(moddatetime); 28 29 Datum 30 moddatetime(PG_FUNCTION_ARGS) 31 { 32 TriggerData *trigdata = (TriggerData *) fcinfo->context; 33 Trigger *trigger; /* to get trigger name */ 34 int nargs; /* # of arguments */ 35 int attnum; /* positional number of field to change */ 36 Oid atttypid; /* type OID of field to change */ 37 Datum newdt; /* The current datetime. */ 38 bool newdtnull; /* null flag for it */ 39 char **args; /* arguments */ 40 char *relname; /* triggered relation name */ 41 Relation rel; /* triggered relation */ 42 HeapTuple rettuple = NULL; 43 TupleDesc tupdesc; /* tuple description */ 44 45 if (!CALLED_AS_TRIGGER(fcinfo)) 46 /* internal error */ 47 elog(ERROR, "moddatetime: not fired by trigger manager"); 48 49 if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) 50 /* internal error */ 51 elog(ERROR, "moddatetime: must be fired for row"); 52 53 if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event)) 54 /* internal error */ 55 elog(ERROR, "moddatetime: must be fired before event"); 56 57 if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event)) 58 /* internal error */ 59 elog(ERROR, "moddatetime: cannot process INSERT events"); 60 else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event)) 61 rettuple = trigdata->tg_newtuple; 62 else 63 /* internal error */ 64 elog(ERROR, "moddatetime: cannot process DELETE events"); 65 66 rel = trigdata->tg_relation; 67 relname = SPI_getrelname(rel); 68 69 trigger = trigdata->tg_trigger; 70 71 nargs = trigger->tgnargs; 72 73 if (nargs != 1) 74 /* internal error */ 75 elog(ERROR, "moddatetime (%s): A single argument was expected", relname); 76 77 args = trigger->tgargs; 78 /* must be the field layout? */ 79 tupdesc = rel->rd_att; 80 81 /* 82 * This gets the position in the tuple of the field we want. args[0] being 83 * the name of the field to update, as passed in from the trigger. 84 */ 85 attnum = SPI_fnumber(tupdesc, args[0]); 86 87 /* 88 * This is where we check to see if the field we are supposed to update 89 * even exists. 90 */ 91 if (attnum <= 0) 92 ereport(ERROR, 93 (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION), 94 errmsg("\"%s\" has no attribute \"%s\"", 95 relname, args[0]))); 96 97 /* 98 * Check the target field has an allowed type, and get the current 99 * datetime as a value of that type. 100 */ 101 atttypid = SPI_gettypeid(tupdesc, attnum); 102 if (atttypid == TIMESTAMPOID) 103 newdt = DirectFunctionCall3(timestamp_in, 104 CStringGetDatum("now"), 105 ObjectIdGetDatum(InvalidOid), 106 Int32GetDatum(-1)); 107 else if (atttypid == TIMESTAMPTZOID) 108 newdt = DirectFunctionCall3(timestamptz_in, 109 CStringGetDatum("now"), 110 ObjectIdGetDatum(InvalidOid), 111 Int32GetDatum(-1)); 112 else 113 { 114 ereport(ERROR, 115 (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION), 116 errmsg("attribute \"%s\" of \"%s\" must be type TIMESTAMP or TIMESTAMPTZ", 117 args[0], relname))); 118 newdt = (Datum) 0; /* keep compiler quiet */ 119 } 120 newdtnull = false; 121 122 /* Replace the attnum'th column with newdt */ 123 rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc, 124 1, &attnum, &newdt, &newdtnull); 125 126 /* Clean up */ 127 pfree(relname); 128 129 return PointerGetDatum(rettuple); 130 } 131