contrib/spi/insert_username.c

   1 /*
   2  * insert_username.c
   3  * $Modified: Thu Oct 16 08:13:42 1997 by brook $
   4  * $PostgreSQL$
   5  *
   6  * insert user name in response to a trigger
   7  * usage:  insert_username (column_name)
   8  */
   9
  10 #include "executor/spi.h"               /* this is what you need to work with SPI */
  11 #include "commands/trigger.h"   /* -"- and triggers */
  12 #include "miscadmin.h"                  /* for GetUserName() */
  13
  14 PG_MODULE_MAGIC;
  15
  16 extern Datum insert_username(PG_FUNCTION_ARGS);
  17
  18 PG_FUNCTION_INFO_V1(insert_username);
  19
  20 Datum
  21 insert_username(PG_FUNCTION_ARGS)
  22 {
  23         TriggerData *trigdata = (TriggerData *) fcinfo->context;
  24         Trigger    *trigger;            /* to get trigger name */
  25         int                     nargs;                  /* # of arguments */
  26         Datum           newval;                 /* new value of column */
  27         char      **args;                       /* arguments */
  28         char       *relname;            /* triggered relation name */
  29         Relation        rel;                    /* triggered relation */
  30         HeapTuple       rettuple = NULL;
  31         TupleDesc       tupdesc;                /* tuple description */
  32         int                     attnum;
  33
  34         /* sanity checks from autoinc.c */
  35         if (!CALLED_AS_TRIGGER(fcinfo))
  36                 /* internal error */
  37                 elog(ERROR, "insert_username: not fired by trigger manager");
  38         if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
  39                 /* internal error */
  40                 elog(ERROR, "insert_username: cannot process STATEMENT events");
  41         if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
  42                 /* internal error */
  43                 elog(ERROR, "insert_username: must be fired before event");
  44
  45         if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
  46                 rettuple = trigdata->tg_trigtuple;
  47         else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
  48                 rettuple = trigdata->tg_newtuple;
  49         else
  50                 /* internal error */
  51                 elog(ERROR, "insert_username: cannot process DELETE events");
  52
  53         rel = trigdata->tg_relation;
  54         relname = SPI_getrelname(rel);
  55
  56         trigger = trigdata->tg_trigger;
  57
  58         nargs = trigger->tgnargs;
  59         if (nargs != 1)
  60                 /* internal error */
  61                 elog(ERROR, "insert_username (%s): one argument was expected", relname);
  62
  63         args = trigger->tgargs;
  64         tupdesc = rel->rd_att;
  65
  66         attnum = SPI_fnumber(tupdesc, args[0]);
  67
  68         if (attnum < 0)
  69                 ereport(ERROR,
  70                                 (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
  71                                  errmsg("\"%s\" has no attribute \"%s\"", relname, args[0])));
  72
  73         if (SPI_gettypeid(tupdesc, attnum) != TEXTOID)
  74                 ereport(ERROR,
  75                                 (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
  76                                  errmsg("attribute \"%s\" of \"%s\" must be type TEXT",
  77                                                 args[0], relname)));
  78
  79         /* create fields containing name */
  80         newval = CStringGetTextDatum(GetUserNameFromId(GetUserId()));
  81
  82         /* construct new tuple */
  83         rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, &newval, NULL);
  84         if (rettuple == NULL)
  85                 /* internal error */
  86                 elog(ERROR, "insert_username (\"%s\"): %d returned by SPI_modifytuple",
  87                          relname, SPI_result);
  88
  89         pfree(relname);
  90
  91         return PointerGetDatum(rettuple);
  92 }