contrib/lo/lo.c

   1 /*
   2  *      PostgreSQL definitions for managed Large Objects.
   3  *
   4  *      $PostgreSQL: pgsql/contrib/lo/lo.c,v 1.15 2005/06/23 00:06:37 tgl Exp $
   5  *
   6  */
   7
   8 #include "postgres.h"
   9
  10 /* Required for largeobjects */
  11 #include "libpq/libpq-fs.h"
  12 #include "libpq/be-fsstubs.h"
  13
  14 /* Required for SPI */
  15 #include "executor/spi.h"
  16
  17 /* Required for triggers */
  18 #include "commands/trigger.h"
  19
  20
  21 #define atooid(x)  ((Oid) strtoul((x), NULL, 10))
  22
  23
  24 /* forward declarations */
  25 Datum           lo_manage(PG_FUNCTION_ARGS);
  26
  27
  28 /*
  29  * This is the trigger that protects us from orphaned large objects
  30  */
  31 PG_FUNCTION_INFO_V1(lo_manage);
  32
  33 Datum
  34 lo_manage(PG_FUNCTION_ARGS)
  35 {
  36         TriggerData *trigdata = (TriggerData *) fcinfo->context;
  37         int                     attnum;                 /* attribute number to monitor  */
  38         char      **args;                       /* Args containing attr name    */
  39         TupleDesc       tupdesc;                /* Tuple Descriptor                             */
  40         HeapTuple       rettuple;               /* Tuple to be returned                 */
  41         bool            isdelete;               /* are we deleting?                             */
  42         HeapTuple       newtuple;               /* The new value for tuple              */
  43         HeapTuple       trigtuple;              /* The original value of tuple  */
  44
  45         if (!CALLED_AS_TRIGGER(fcinfo))         /* internal error */
  46                 elog(ERROR, "not fired by trigger manager");
  47
  48         /*
  49          * Fetch some values from trigdata
  50          */
  51         newtuple = trigdata->tg_newtuple;
  52         trigtuple = trigdata->tg_trigtuple;
  53         tupdesc = trigdata->tg_relation->rd_att;
  54         args = trigdata->tg_trigger->tgargs;
  55
  56         /* tuple to return to Executor */
  57         if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
  58                 rettuple = newtuple;
  59         else
  60                 rettuple = trigtuple;
  61
  62         /* Are we deleting the row? */
  63         isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
  64
  65         /* Get the column we're interested in */
  66         attnum = SPI_fnumber(tupdesc, args[0]);
  67
  68         if (attnum <= 0)
  69                 elog(ERROR, "column \"%s\" does not exist", args[0]);
  70
  71         /*
  72          * Handle updates
  73          *
  74          * Here, if the value of the monitored attribute changes, then the large
  75          * object associated with the original value is unlinked.
  76          */
  77         if (newtuple != NULL)
  78         {
  79                 char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
  80                 char       *newv = SPI_getvalue(newtuple, tupdesc, attnum);
  81
  82                 if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
  83                         DirectFunctionCall1(lo_unlink,
  84                                                                 ObjectIdGetDatum(atooid(orig)));
  85
  86                 if (newv)
  87                         pfree(newv);
  88                 if (orig)
  89                         pfree(orig);
  90         }
  91
  92         /*
  93          * Handle deleting of rows
  94          *
  95          * Here, we unlink the large object associated with the managed attribute
  96          */
  97         if (isdelete)
  98         {
  99                 char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
 100
 101                 if (orig != NULL)
 102                 {
 103                         DirectFunctionCall1(lo_unlink,
 104                                                                 ObjectIdGetDatum(atooid(orig)));
 105
 106                         pfree(orig);
 107                 }
 108         }
 109
 110         return PointerGetDatum(rettuple);
 111 }