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