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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 "commands/trigger.h" 21 : #include "executor/spi.h" 22 : #include "utils/builtins.h" 23 : #include "utils/rel.h" 24 : 25 0 : PG_MODULE_MAGIC; 26 : 27 0 : PG_FUNCTION_INFO_V1(moddatetime); 28 : 29 : Datum 30 0 : moddatetime(PG_FUNCTION_ARGS) 31 : { 32 0 : 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 0 : HeapTuple rettuple = NULL; 43 : TupleDesc tupdesc; /* tuple description */ 44 : 45 0 : if (!CALLED_AS_TRIGGER(fcinfo)) 46 : /* internal error */ 47 0 : elog(ERROR, "moddatetime: not fired by trigger manager"); 48 : 49 0 : if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) 50 : /* internal error */ 51 0 : elog(ERROR, "moddatetime: must be fired for row"); 52 : 53 0 : if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event)) 54 : /* internal error */ 55 0 : elog(ERROR, "moddatetime: must be fired before event"); 56 : 57 0 : if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event)) 58 : /* internal error */ 59 0 : elog(ERROR, "moddatetime: cannot process INSERT events"); 60 0 : else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event)) 61 0 : rettuple = trigdata->tg_newtuple; 62 : else 63 : /* internal error */ 64 0 : elog(ERROR, "moddatetime: cannot process DELETE events"); 65 : 66 0 : rel = trigdata->tg_relation; 67 0 : relname = SPI_getrelname(rel); 68 : 69 0 : trigger = trigdata->tg_trigger; 70 : 71 0 : nargs = trigger->tgnargs; 72 : 73 0 : if (nargs != 1) 74 : /* internal error */ 75 0 : elog(ERROR, "moddatetime (%s): A single argument was expected", relname); 76 : 77 0 : args = trigger->tgargs; 78 : /* must be the field layout? */ 79 0 : 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 0 : 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 0 : if (attnum <= 0) 92 0 : 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 0 : atttypid = SPI_gettypeid(tupdesc, attnum); 102 0 : if (atttypid == TIMESTAMPOID) 103 0 : newdt = DirectFunctionCall3(timestamp_in, 104 : CStringGetDatum("now"), 105 : ObjectIdGetDatum(InvalidOid), 106 : Int32GetDatum(-1)); 107 0 : else if (atttypid == TIMESTAMPTZOID) 108 0 : newdt = DirectFunctionCall3(timestamptz_in, 109 : CStringGetDatum("now"), 110 : ObjectIdGetDatum(InvalidOid), 111 : Int32GetDatum(-1)); 112 : else 113 : { 114 0 : 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 0 : newdtnull = false; 121 : 122 : /* Replace the attnum'th column with newdt */ 123 0 : rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc, 124 : 1, &attnum, &newdt, &newdtnull); 125 : 126 : /* Clean up */ 127 0 : pfree(relname); 128 : 129 0 : return PointerGetDatum(rettuple); 130 : }