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Viewing changes to contrib/lo/lo.c

  • Committer: Bazaar Package Importer
  • Author(s): Martin Pitt
  • Date: 2009-03-20 12:00:13 UTC
  • Revision ID: james.westby@ubuntu.com-20090320120013-hogj7egc5mjncc5g
Tags: upstream-8.4~0cvs20090328
Import upstream version 8.4~0cvs20090328

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contrib/lo/lo.c
 
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/*
 
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 *      PostgreSQL definitions for managed Large Objects.
 
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 *
 
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 *      $PostgreSQL$
 
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 *
 
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 */
 
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#include "postgres.h"
 
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/* Required for SPI */
 
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#include "executor/spi.h"
 
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/* Required for largeobjects */
 
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#include "libpq/be-fsstubs.h"
 
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#include "libpq/libpq-fs.h"
 
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/* Required for triggers */
 
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#include "commands/trigger.h"
 
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PG_MODULE_MAGIC;
 
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#define atooid(x)  ((Oid) strtoul((x), NULL, 10))
 
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/* forward declarations */
 
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Datum           lo_manage(PG_FUNCTION_ARGS);
 
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/*
 
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 * This is the trigger that protects us from orphaned large objects
 
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 */
 
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PG_FUNCTION_INFO_V1(lo_manage);
 
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Datum
 
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lo_manage(PG_FUNCTION_ARGS)
 
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{
 
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        TriggerData *trigdata = (TriggerData *) fcinfo->context;
 
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        int                     attnum;                 /* attribute number to monitor  */
 
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        char      **args;                       /* Args containing attr name    */
 
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        TupleDesc       tupdesc;                /* Tuple Descriptor                             */
 
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        HeapTuple       rettuple;               /* Tuple to be returned                 */
 
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        bool            isdelete;               /* are we deleting?                             */
 
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        HeapTuple       newtuple;               /* The new value for tuple              */
 
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        HeapTuple       trigtuple;              /* The original value of tuple  */
 
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        if (!CALLED_AS_TRIGGER(fcinfo))         /* internal error */
 
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                elog(ERROR, "not fired by trigger manager");
 
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        /*
 
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         * Fetch some values from trigdata
 
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         */
 
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        newtuple = trigdata->tg_newtuple;
 
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        trigtuple = trigdata->tg_trigtuple;
 
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        tupdesc = trigdata->tg_relation->rd_att;
 
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        args = trigdata->tg_trigger->tgargs;
 
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        /* tuple to return to Executor */
 
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        if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
 
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                rettuple = newtuple;
 
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        else
 
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                rettuple = trigtuple;
 
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        /* Are we deleting the row? */
 
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        isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
 
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        /* Get the column we're interested in */
 
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        attnum = SPI_fnumber(tupdesc, args[0]);
 
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        if (attnum <= 0)
 
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                elog(ERROR, "column \"%s\" does not exist", args[0]);
 
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        /*
 
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         * Handle updates
 
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         *
 
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         * Here, if the value of the monitored attribute changes, then the large
 
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         * object associated with the original value is unlinked.
 
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         */
 
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        if (newtuple != NULL)
 
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        {
 
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                char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
 
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                char       *newv = SPI_getvalue(newtuple, tupdesc, attnum);
 
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                if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
 
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                        DirectFunctionCall1(lo_unlink,
 
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                                                                ObjectIdGetDatum(atooid(orig)));
 
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                if (newv)
 
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                        pfree(newv);
 
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                if (orig)
 
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                        pfree(orig);
 
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        }
 
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        /*
 
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         * Handle deleting of rows
 
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         *
 
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         * Here, we unlink the large object associated with the managed attribute
 
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         */
 
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        if (isdelete)
 
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        {
 
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                char       *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
 
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                if (orig != NULL)
 
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                {
 
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                        DirectFunctionCall1(lo_unlink,
 
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                                                                ObjectIdGetDatum(atooid(orig)));
 
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                        pfree(orig);
 
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                }
 
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        }
 
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        return PointerGetDatum(rettuple);
 
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}