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            1 : 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            2 : PG_FUNCTION_INFO_V1(lo_manage);
      25              : 
      26              : Datum
      27            8 : lo_manage(PG_FUNCTION_ARGS)
      28              : {
      29            8 :     TriggerData *trigdata = (TriggerData *) fcinfo->context;
      30              :     int         attnum;         /* attribute number to monitor  */
      31              :     char      **args;           /* Args containing attr name    */
      32              :     TupleDesc   tupdesc;        /* Tuple Descriptor             */
      33              :     HeapTuple   rettuple;       /* Tuple to be returned         */
      34              :     bool        isdelete;       /* are we deleting?             */
      35              :     HeapTuple   newtuple;       /* The new value for tuple      */
      36              :     HeapTuple   trigtuple;      /* The original value of tuple  */
      37              : 
      38            8 :     if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
      39            0 :         elog(ERROR, "lo_manage: not fired by trigger manager");
      40              : 
      41            8 :     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            8 :     newtuple = trigdata->tg_newtuple;
      49            8 :     trigtuple = trigdata->tg_trigtuple;
      50            8 :     tupdesc = trigdata->tg_relation->rd_att;
      51            8 :     args = trigdata->tg_trigger->tgargs;
      52              : 
      53            8 :     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            8 :     if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
      59            6 :         rettuple = newtuple;
      60              :     else
      61            2 :         rettuple = trigtuple;
      62              : 
      63              :     /* Are we deleting the row? */
      64            8 :     isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
      65              : 
      66              :     /* Get the column we're interested in */
      67            8 :     attnum = SPI_fnumber(tupdesc, args[0]);
      68              : 
      69            8 :     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           14 :     if (newtuple != NULL &&
      80            6 :         bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, trigdata->tg_updatedcols))
      81              :     {
      82            3 :         char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
      83            3 :         char       *newv = SPI_getvalue(newtuple, tupdesc, attnum);
      84              : 
      85            3 :         if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
      86            3 :             DirectFunctionCall1(be_lo_unlink,
      87              :                                 ObjectIdGetDatum(atooid(orig)));
      88              : 
      89            3 :         if (newv)
      90            3 :             pfree(newv);
      91            3 :         if (orig)
      92            3 :             pfree(orig);
      93              :     }
      94              : 
      95              :     /*
      96              :      * Handle deleting of rows
      97              :      *
      98              :      * Here, we unlink the large object associated with the managed attribute
      99              :      */
     100            8 :     if (isdelete)
     101              :     {
     102            2 :         char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
     103              : 
     104            2 :         if (orig != NULL)
     105              :         {
     106            2 :             DirectFunctionCall1(be_lo_unlink,
     107              :                                 ObjectIdGetDatum(atooid(orig)));
     108              : 
     109            2 :             pfree(orig);
     110              :         }
     111              :     }
     112              : 
     113            8 :     return PointerGetDatum(rettuple);
     114              : }