greenplumn lo 源码
greenplumn lo 代码
文件路径：/contrib/lo/lo.c
/*
* PostgreSQL definitions for managed Large Objects.
*
* contrib/lo/lo.c
*
*/
#include "postgres.h"
#include "commands/trigger.h"
#include "executor/spi.h"
#include "utils/builtins.h"
#include "utils/rel.h"
PG_MODULE_MAGIC;
/*
* 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, "%s: not fired by trigger manager",
trigdata->tg_trigger->tgname);
if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) /* internal error */
elog(ERROR, "%s: must be fired for row",
trigdata->tg_trigger->tgname);
/*
* Fetch some values from trigdata
*/
newtuple = trigdata->tg_newtuple;
trigtuple = trigdata->tg_trigtuple;
tupdesc = trigdata->tg_relation->rd_att;
args = trigdata->tg_trigger->tgargs;
if (args == NULL) /* internal error */
elog(ERROR, "%s: no column name provided in the trigger definition",
trigdata->tg_trigger->tgname);
/* 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, "%s: column \"%s\" does not exist",
trigdata->tg_trigger->tgname, 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(be_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(be_lo_unlink,
ObjectIdGetDatum(atooid(orig)));
pfree(orig);
}
}
return PointerGetDatum(rettuple);
}
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