Line data    Source code

       1              : /*
       2              :  *      PostgreSQL definitions for managed Large Objects.
       3              :  *
       4              :  *      contrib/lo/lo.c
       5              :  *
       6              :  */
       7              : 
       8              : #include "postgres.h"
       9              : 
      10              : #include "commands/trigger.h"
      11              : #include "executor/spi.h"
      12              : #include "utils/fmgrprotos.h"
      13              : #include "utils/rel.h"
      14              : 
      15            0 : PG_MODULE_MAGIC_EXT(
      16              :                                         .name = "lo",
      17              :                                         .version = PG_VERSION
      18              : );
      19              : 
      20              : 
      21              : /*
      22              :  * This is the trigger that protects us from orphaned large objects
      23              :  */
      24            0 : PG_FUNCTION_INFO_V1(lo_manage);
      25              : 
      26              : Datum
      27            0 : lo_manage(PG_FUNCTION_ARGS)
      28              : {
      29            0 :         TriggerData *trigdata = (TriggerData *) fcinfo->context;
      30            0 :         int                     attnum;                 /* attribute number to monitor  */
      31            0 :         char      **args;                       /* Args containing attr name    */
      32            0 :         TupleDesc       tupdesc;                /* Tuple Descriptor                             */
      33            0 :         HeapTuple       rettuple;               /* Tuple to be returned                 */
      34            0 :         bool            isdelete;               /* are we deleting?                             */
      35            0 :         HeapTuple       newtuple;               /* The new value for tuple              */
      36            0 :         HeapTuple       trigtuple;              /* The original value of tuple  */
      37              : 
      38            0 :         if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
      39            0 :                 elog(ERROR, "lo_manage: not fired by trigger manager");
      40              : 
      41            0 :         if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) /* internal error */
      42            0 :                 elog(ERROR, "%s: must be fired for row",
      43              :                          trigdata->tg_trigger->tgname);
      44              : 
      45              :         /*
      46              :          * Fetch some values from trigdata
      47              :          */
      48            0 :         newtuple = trigdata->tg_newtuple;
      49            0 :         trigtuple = trigdata->tg_trigtuple;
      50            0 :         tupdesc = trigdata->tg_relation->rd_att;
      51            0 :         args = trigdata->tg_trigger->tgargs;
      52              : 
      53            0 :         if (args == NULL)                       /* internal error */
      54            0 :                 elog(ERROR, "%s: no column name provided in the trigger definition",
      55              :                          trigdata->tg_trigger->tgname);
      56              : 
      57              :         /* tuple to return to Executor */
      58            0 :         if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
      59            0 :                 rettuple = newtuple;
      60              :         else
      61            0 :                 rettuple = trigtuple;
      62              : 
      63              :         /* Are we deleting the row? */
      64            0 :         isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
      65              : 
      66              :         /* Get the column we're interested in */
      67            0 :         attnum = SPI_fnumber(tupdesc, args[0]);
      68              : 
      69            0 :         if (attnum <= 0)
      70            0 :                 elog(ERROR, "%s: column \"%s\" does not exist",
      71              :                          trigdata->tg_trigger->tgname, args[0]);
      72              : 
      73              :         /*
      74              :          * Handle updates
      75              :          *
      76              :          * Here, if the value of the monitored attribute changes, then the large
      77              :          * object associated with the original value is unlinked.
      78              :          */
      79            0 :         if (newtuple != NULL &&
      80            0 :                 bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, trigdata->tg_updatedcols))
      81              :         {
      82            0 :                 char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
      83            0 :                 char       *newv = SPI_getvalue(newtuple, tupdesc, attnum);
      84              : 
      85            0 :                 if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
      86            0 :                         DirectFunctionCall1(be_lo_unlink,
      87              :                                                                 ObjectIdGetDatum(atooid(orig)));
      88              : 
      89            0 :                 if (newv)
      90            0 :                         pfree(newv);
      91            0 :                 if (orig)
      92            0 :                         pfree(orig);
      93            0 :         }
      94              : 
      95              :         /*
      96              :          * Handle deleting of rows
      97              :          *
      98              :          * Here, we unlink the large object associated with the managed attribute
      99              :          */
     100            0 :         if (isdelete)
     101              :         {
     102            0 :                 char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
     103              : 
     104            0 :                 if (orig != NULL)
     105              :                 {
     106            0 :                         DirectFunctionCall1(be_lo_unlink,
     107              :                                                                 ObjectIdGetDatum(atooid(orig)));
     108              : 
     109            0 :                         pfree(orig);
     110            0 :                 }
     111            0 :         }
     112              : 
     113            0 :         return PointerGetDatum(rettuple);
     114            0 : }