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Sourcecode: postgresql-8.4 version File versions

lo.c

/*
 *    PostgreSQL definitions for managed Large Objects.
 *
 *    $PostgreSQL$
 *
 */

#include "postgres.h"

/* Required for SPI */
#include "executor/spi.h"

/* Required for largeobjects */
#include "libpq/be-fsstubs.h"
#include "libpq/libpq-fs.h"

/* Required for triggers */
#include "commands/trigger.h"

PG_MODULE_MAGIC;

#define atooid(x)  ((Oid) strtoul((x), NULL, 10))


/* forward declarations */
Datum       lo_manage(PG_FUNCTION_ARGS);


/*
 * This is the trigger that protects us from orphaned large objects
 */
PG_FUNCTION_INFO_V1(lo_manage);

Datum
lo_manage(PG_FUNCTION_ARGS)
{
      TriggerData *trigdata = (TriggerData *) fcinfo->context;
      int               attnum;                 /* attribute number to monitor      */
      char    **args;               /* Args containing attr name  */
      TupleDesc   tupdesc;          /* Tuple Descriptor                       */
      HeapTuple   rettuple;         /* Tuple to be returned             */
      bool        isdelete;         /* are we deleting?                       */
      HeapTuple   newtuple;         /* The new value for tuple          */
      HeapTuple   trigtuple;        /* The original value of tuple      */

      if (!CALLED_AS_TRIGGER(fcinfo))           /* internal error */
            elog(ERROR, "not fired by trigger manager");

      /*
       * Fetch some values from trigdata
       */
      newtuple = trigdata->tg_newtuple;
      trigtuple = trigdata->tg_trigtuple;
      tupdesc = trigdata->tg_relation->rd_att;
      args = trigdata->tg_trigger->tgargs;

      /* tuple to return to Executor */
      if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
            rettuple = newtuple;
      else
            rettuple = trigtuple;

      /* Are we deleting the row? */
      isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);

      /* Get the column we're interested in */
      attnum = SPI_fnumber(tupdesc, args[0]);

      if (attnum <= 0)
            elog(ERROR, "column \"%s\" does not exist", args[0]);

      /*
       * Handle updates
       *
       * Here, if the value of the monitored attribute changes, then the large
       * object associated with the original value is unlinked.
       */
      if (newtuple != NULL)
      {
            char     *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
            char     *newv = SPI_getvalue(newtuple, tupdesc, attnum);

            if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
                  DirectFunctionCall1(lo_unlink,
                                                ObjectIdGetDatum(atooid(orig)));

            if (newv)
                  pfree(newv);
            if (orig)
                  pfree(orig);
      }

      /*
       * Handle deleting of rows
       *
       * Here, we unlink the large object associated with the managed attribute
       */
      if (isdelete)
      {
            char     *orig = SPI_getvalue(trigtuple, tupdesc, attnum);

            if (orig != NULL)
            {
                  DirectFunctionCall1(lo_unlink,
                                                ObjectIdGetDatum(atooid(orig)));

                  pfree(orig);
            }
      }

      return PointerGetDatum(rettuple);
}

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