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           2 : 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           4 : PG_FUNCTION_INFO_V1(lo_manage);
      25             : 
      26             : Datum
      27          16 : lo_manage(PG_FUNCTION_ARGS)
      28             : {
      29          16 :     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          16 :     if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
      39           0 :         elog(ERROR, "lo_manage: not fired by trigger manager");
      40             : 
      41          16 :     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          16 :     newtuple = trigdata->tg_newtuple;
      49          16 :     trigtuple = trigdata->tg_trigtuple;
      50          16 :     tupdesc = trigdata->tg_relation->rd_att;
      51          16 :     args = trigdata->tg_trigger->tgargs;
      52             : 
      53          16 :     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          16 :     if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
      59          12 :         rettuple = newtuple;
      60             :     else
      61           4 :         rettuple = trigtuple;
      62             : 
      63             :     /* Are we deleting the row? */
      64          16 :     isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
      65             : 
      66             :     /* Get the column we're interested in */
      67          16 :     attnum = SPI_fnumber(tupdesc, args[0]);
      68             : 
      69          16 :     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          28 :     if (newtuple != NULL &&
      80          12 :         bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, trigdata->tg_updatedcols))
      81             :     {
      82           6 :         char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
      83           6 :         char       *newv = SPI_getvalue(newtuple, tupdesc, attnum);
      84             : 
      85           6 :         if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
      86           6 :             DirectFunctionCall1(be_lo_unlink,
      87             :                                 ObjectIdGetDatum(atooid(orig)));
      88             : 
      89           6 :         if (newv)
      90           6 :             pfree(newv);
      91           6 :         if (orig)
      92           6 :             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          16 :     if (isdelete)
     101             :     {
     102           4 :         char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
     103             : 
     104           4 :         if (orig != NULL)
     105             :         {
     106           4 :             DirectFunctionCall1(be_lo_unlink,
     107             :                                 ObjectIdGetDatum(atooid(orig)));
     108             : 
     109           4 :             pfree(orig);
     110             :         }
     111             :     }
     112             : 
     113          16 :     return PointerGetDatum(rettuple);
     114             : }