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113 lines
2.5 KiB
C
113 lines
2.5 KiB
C
/*
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* PostgreSQL definitions for managed Large Objects.
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*
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* contrib/lo/lo.c
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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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}
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