Passing a NULL Connection (Server)

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Passing a NULL Connection (Server)

Many functions in the smart-large-object interface take a connection descriptor as a parameter. However, many of the functions also accept a NULL-valued pointer as a connection descriptor. Use of a NULL-valued connection descriptor has the following performance impact:

The smart-large-object functions do not need to check the validity of a connection descriptor.
The calling code is not required to open and close a connection.

To improve performance, you can pass a NULL-valued pointer as a connection descriptor to any of the following functions of the smart-large-object interface:

mi_lo_alter( )
mi_lo_close( )
mi_lo_colinfo_by_ids( )
mi_lo_colinfo_by_name( )
mi_lo_copy( )
mi_lo_create( )
mi_lo_decrefcount( )
mi_lo_delete_immediate( )
mi_lo_expand( )
mi_lo_filename( )
mi_lo_from_buffer( )
mi_lo_from_file( )
mi_lo_from_file_by_lofd( )
mi_lo_increfcount( )
mi_lo_invalidate( )
mi_lo_lock( )
mi_lo_lolist_create( )
mi_lo_open( )

mi_lo_spec_init( )
mi_lo_stat( )
mi_lo_stat_free( )
mi_lo_tell( )
mi_lo_to_buffer( )
mi_lo_to_file( )
mi_lo_truncate( )
mi_lo_unlock( )
mi_lo_utimes( )
mi_lo_validate( )
mi_lo_write( )
mi_lo_writewithseek( )
mi_lo_ptr_cmp( )
mi_lo_read( )
mi_lo_readwithseek( )
mi_lo_release( )
mi_lo_seek( )
mi_lo_spec_free( )

The following code fragment passes a valid connection descriptor to the mi_lo_alter( ) function:

conn = mi_open(NULL, NULL, NULL);
if ( mi_lo_alter(conn, LO_ptr, LO_spec) == MI_ERROR )

/* Code execution does not reach here when a database server
 * exception occurs.
 */
   return MI_ERROR;
mi_close(conn);

When you specify a NULL-valued pointer as a connection descriptor, you can omit the calls to mi_open( ) and mi_close( ), as the following code fragment shows:

if ( mi_lo_alter(NULL, LO_ptr, LO_spec) == MI_ERROR )

/* Code execution does not reach here when a database server
 * exception occurs.
 */
   return MI_ERROR;