@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $ PostgreSQL : pgsql / src / backend / storage / large_object / inv_api . c , v 1.110 2005 / 04 / 14 20 : 03 : 25 tgl Exp $
* $ PostgreSQL : pgsql / src / backend / storage / large_object / inv_api . c , v 1.111 2005 / 06 / 13 02 : 26 : 49 tgl Exp $
*
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
*/
@ -114,6 +114,42 @@ close_lo_relation(bool isCommit)
}
/*
* Same as pg_largeobject . c ' s LargeObjectExists ( ) , except snapshot to
* read with can be specified .
*/
static bool
myLargeObjectExists ( Oid loid , Snapshot snapshot )
{
bool retval = false ;
Relation pg_largeobject ;
ScanKeyData skey [ 1 ] ;
SysScanDesc sd ;
/*
* See if we can find any tuples belonging to the specified LO
*/
ScanKeyInit ( & skey [ 0 ] ,
Anum_pg_largeobject_loid ,
BTEqualStrategyNumber , F_OIDEQ ,
ObjectIdGetDatum ( loid ) ) ;
pg_largeobject = heap_open ( LargeObjectRelationId , AccessShareLock ) ;
sd = systable_beginscan ( pg_largeobject , LargeObjectLOidPNIndexId , true ,
snapshot , 1 , skey ) ;
if ( systable_getnext ( sd ) ! = NULL )
retval = true ;
systable_endscan ( sd ) ;
heap_close ( pg_largeobject , AccessShareLock ) ;
return retval ;
}
static int32
getbytealen ( bytea * data )
{
@ -125,58 +161,44 @@ getbytealen(bytea *data)
/*
* inv_create - - create a new large object .
* inv_create - - create a new large object
*
* Arguments :
* flags
* lobjId - OID to use for new large object , or InvalidOid to pick one
*
* Returns :
* large object descriptor , appropriately filled in .
* OID of new object
*
* If lobjId is not InvalidOid , then an error occurs if the OID is already
* in use .
*/
LargeObjectDesc *
inv_create ( int flags )
Oid
inv_create ( Oid lobjId )
{
Oid file_oid ;
LargeObjectDesc * retval ;
/*
* Allocate an OID to be the LO ' s identifier .
* Allocate an OID to be the LO ' s identifier , unless we were told
* what to use . In event of collision with an existing ID , loop
* to find a free one .
*/
file_oid = newoid ( ) ;
/* Check for duplicate (shouldn't happen) */
if ( LargeObjectExists ( file_oid ) )
elog ( ERROR , " large object %u already exists " , file_oid ) ;
if ( ! OidIsValid ( lobjId ) )
{
do {
lobjId = newoid ( ) ;
} while ( LargeObjectExists ( lobjId ) ) ;
}
/*
* Create the LO by writing an empty first page for it in
* pg_largeobject
* pg_largeobject ( will fail if duplicate )
*/
LargeObjectCreate ( file_oi d) ;
LargeObjectCreate ( lobjI d) ;
/*
* Advance command counter so that new tuple will be seen by later
* large - object operations in this transaction .
* Advance command counter to make new tuple visible to later operations .
*/
CommandCounterIncrement ( ) ;
/*
* Prepare LargeObjectDesc data structure for accessing LO
*/
retval = ( LargeObjectDesc * ) palloc ( sizeof ( LargeObjectDesc ) ) ;
retval - > id = file_oid ;
retval - > subid = GetCurrentSubTransactionId ( ) ;
retval - > offset = 0 ;
if ( flags & INV_WRITE )
retval - > flags = IFS_WRLOCK | IFS_RDLOCK ;
else if ( flags & INV_READ )
retval - > flags = IFS_RDLOCK ;
else
elog ( ERROR , " invalid flags: %d " , flags ) ;
return retval ;
return lobjId ;
}
/*
@ -190,11 +212,6 @@ inv_open(Oid lobjId, int flags)
{
LargeObjectDesc * retval ;
if ( ! LargeObjectExists ( lobjId ) )
ereport ( ERROR ,
( errcode ( ERRCODE_UNDEFINED_OBJECT ) ,
errmsg ( " large object %u does not exist " , lobjId ) ) ) ;
retval = ( LargeObjectDesc * ) palloc ( sizeof ( LargeObjectDesc ) ) ;
retval - > id = lobjId ;
@ -202,12 +219,25 @@ inv_open(Oid lobjId, int flags)
retval - > offset = 0 ;
if ( flags & INV_WRITE )
{
retval - > snapshot = SnapshotNow ;
retval - > flags = IFS_WRLOCK | IFS_RDLOCK ;
}
else if ( flags & INV_READ )
{
/* be sure to copy snap into fscxt */
retval - > snapshot = CopySnapshot ( ActiveSnapshot ) ;
retval - > flags = IFS_RDLOCK ;
}
else
elog ( ERROR , " invalid flags: %d " , flags ) ;
/* Can't use LargeObjectExists here because it always uses SnapshotNow */
if ( ! myLargeObjectExists ( lobjId , retval - > snapshot ) )
ereport ( ERROR ,
( errcode ( ERRCODE_UNDEFINED_OBJECT ) ,
errmsg ( " large object %u does not exist " , lobjId ) ) ) ;
return retval ;
}
@ -218,6 +248,8 @@ void
inv_close ( LargeObjectDesc * obj_desc )
{
Assert ( PointerIsValid ( obj_desc ) ) ;
if ( obj_desc - > snapshot ! = SnapshotNow )
FreeSnapshot ( obj_desc - > snapshot ) ;
pfree ( obj_desc ) ;
}
@ -268,7 +300,7 @@ inv_getsize(LargeObjectDesc *obj_desc)
ObjectIdGetDatum ( obj_desc - > id ) ) ;
sd = index_beginscan ( lo_heap_r , lo_index_r ,
SnapshotNow , 1 , skey ) ;
obj_desc - > snapshot , 1 , skey ) ;
/*
* Because the pg_largeobject index is on both loid and pageno , but we
@ -379,7 +411,7 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
Int32GetDatum ( pageno ) ) ;
sd = index_beginscan ( lo_heap_r , lo_index_r ,
SnapshotNow , 2 , skey ) ;
obj_desc - > snapshot , 2 , skey ) ;
while ( ( tuple = index_getnext ( sd , ForwardScanDirection ) ) ! = NULL )
{
@ -470,6 +502,13 @@ inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes)
Assert ( PointerIsValid ( obj_desc ) ) ;
Assert ( buf ! = NULL ) ;
/* enforce writability because snapshot is probably wrong otherwise */
if ( ( obj_desc - > flags & IFS_WRLOCK ) = = 0 )
ereport ( ERROR ,
( errcode ( ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE ) ,
errmsg ( " large object %u was not opened for writing " ,
obj_desc - > id ) ) ) ;
if ( nbytes < = 0 )
return 0 ;
@ -488,7 +527,7 @@ inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes)
Int32GetDatum ( pageno ) ) ;
sd = index_beginscan ( lo_heap_r , lo_index_r ,
SnapshotNow , 2 , skey ) ;
obj_desc - > snapshot , 2 , skey ) ;
oldtuple = NULL ;
olddata = NULL ;
Tom Lane
21 years ago