@ -32,10 +32,14 @@
* ( by opening multiple fd . c temporary files ) . This is an essential feature
* for sorts and hashjoins on large amounts of data .
*
* BufFile supports temporary files that can be made read - only and shared with
* other backends , as infrastructure for parallel execution . Such files need
* to be created as a member of a SharedFileSet that all participants are
* attached to .
* BufFile supports temporary files that can be shared with other backends , as
* infrastructure for parallel execution . Such files need to be created as a
* member of a SharedFileSet that all participants are attached to .
*
* BufFile also supports temporary files that can be used by the single backend
* when the corresponding files need to be survived across the transaction and
* need to be opened and closed multiple times . Such files need to be created
* as a member of a SharedFileSet .
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
*/
@ -277,7 +281,7 @@ BufFileCreateShared(SharedFileSet *fileset, const char *name)
* backends and render it read - only .
*/
BufFile *
BufFileOpenShared ( SharedFileSet * fileset , const char * name )
BufFileOpenShared ( SharedFileSet * fileset , const char * name , int mode )
{
BufFile * file ;
char segment_name [ MAXPGPATH ] ;
@ -301,7 +305,7 @@ BufFileOpenShared(SharedFileSet *fileset, const char *name)
}
/* Try to load a segment. */
SharedSegmentName ( segment_name , name , nfiles ) ;
files [ nfiles ] = SharedFileSetOpen ( fileset , segment_name ) ;
files [ nfiles ] = SharedFileSetOpen ( fileset , segment_name , mode ) ;
if ( files [ nfiles ] < = 0 )
break ;
+ + nfiles ;
@ -321,7 +325,7 @@ BufFileOpenShared(SharedFileSet *fileset, const char *name)
file = makeBufFileCommon ( nfiles ) ;
file - > files = files ;
file - > readOnly = true ; /* Can't write to files opened this way */
file - > readOnly = ( mode = = O_RDONLY ) ? true : false ;
file - > fileset = fileset ;
file - > name = pstrdup ( name ) ;
@ -666,11 +670,21 @@ BufFileSeek(BufFile *file, int fileno, off_t offset, int whence)
newFile = file - > curFile ;
newOffset = ( file - > curOffset + file - > pos ) + offset ;
break ;
# ifdef NOT_USED
case SEEK_END :
/* could be implemented, not needed currently */
/*
* The file size of the last file gives us the end offset of that
* file .
*/
newFile = file - > numFiles - 1 ;
newOffset = FileSize ( file - > files [ file - > numFiles - 1 ] ) ;
if ( newOffset < 0 )
ereport ( ERROR ,
( errcode_for_file_access ( ) ,
errmsg ( " could not determine size of temporary file \" %s \" from BufFile \" %s \" : %m " ,
FilePathName ( file - > files [ file - > numFiles - 1 ] ) ,
file - > name ) ) ) ;
break ;
# endif
default :
elog ( ERROR , " invalid whence: %d " , whence ) ;
return EOF ;
@ -838,3 +852,98 @@ BufFileAppend(BufFile *target, BufFile *source)
return startBlock ;
}
/*
* Truncate a BufFile created by BufFileCreateShared up to the given fileno and
* the offset .
*/
void
BufFileTruncateShared ( BufFile * file , int fileno , off_t offset )
{
int numFiles = file - > numFiles ;
int newFile = fileno ;
off_t newOffset = file - > curOffset ;
char segment_name [ MAXPGPATH ] ;
int i ;
/*
* Loop over all the files up to the given fileno and remove the files
* that are greater than the fileno and truncate the given file up to the
* offset . Note that we also remove the given fileno if the offset is 0
* provided it is not the first file in which we truncate it .
*/
for ( i = file - > numFiles - 1 ; i > = fileno ; i - - )
{
if ( ( i ! = fileno | | offset = = 0 ) & & i ! = 0 )
{
SharedSegmentName ( segment_name , file - > name , i ) ;
FileClose ( file - > files [ i ] ) ;
if ( ! SharedFileSetDelete ( file - > fileset , segment_name , true ) )
ereport ( ERROR ,
( errcode_for_file_access ( ) ,
errmsg ( " could not delete shared fileset \" %s \" : %m " ,
segment_name ) ) ) ;
numFiles - - ;
newOffset = MAX_PHYSICAL_FILESIZE ;
/*
* This is required to indicate that we have deleted the given
* fileno .
*/
if ( i = = fileno )
newFile - - ;
}
else
{
if ( FileTruncate ( file - > files [ i ] , offset ,
WAIT_EVENT_BUFFILE_TRUNCATE ) < 0 )
ereport ( ERROR ,
( errcode_for_file_access ( ) ,
errmsg ( " could not truncate file \" %s \" : %m " ,
FilePathName ( file - > files [ i ] ) ) ) ) ;
newOffset = offset ;
}
}
file - > numFiles = numFiles ;
/*
* If the truncate point is within existing buffer then we can just adjust
* pos within buffer .
*/
if ( newFile = = file - > curFile & &
newOffset > = file - > curOffset & &
newOffset < = file - > curOffset + file - > nbytes )
{
/* No need to reset the current pos if the new pos is greater. */
if ( newOffset < = file - > curOffset + file - > pos )
file - > pos = ( int ) ( newOffset - file - > curOffset ) ;
/* Adjust the nbytes for the current buffer. */
file - > nbytes = ( int ) ( newOffset - file - > curOffset ) ;
}
else if ( newFile = = file - > curFile & &
newOffset < file - > curOffset )
{
/*
* The truncate point is within the existing file but prior to the
* current position , so we can forget the current buffer and reset the
* current position .
*/
file - > curOffset = newOffset ;
file - > pos = 0 ;
file - > nbytes = 0 ;
}
else if ( newFile < file - > curFile )
{
/*
* The truncate point is prior to the current file , so need to reset
* the current position accordingly .
*/
file - > curFile = newFile ;
file - > curOffset = newOffset ;
file - > pos = 0 ;
file - > nbytes = 0 ;
}
/* Nothing to do, if the truncate point is beyond current file. */
}
Amit Kapila
5 years ago