contrib/spi/insert_username.c

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