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Bio::DB::FileCache - In file cache for BioSeq objects


  $cachedb = Bio::DB::FileCache->new($real_db);

  # $real_db is a Bio::DB::RandomAccessI database

  $seq = $cachedb->get_Seq_by_id('ROA1_HUMAN');

  # $seq is a Bio::Seq object

  # more control provided with named-parameter form

  $cachedb = Bio::DB::FileCache->new( -seqdb => $real_db,
                                      -file  => $path,
                                      -keep  => $flag,

This is a disk cache system which saves the objects returned by Bio::DB::RandomAccessI on disk. The disk cache grows without limit, while the process is running, but is automatically unlinked at process termination unless the -keep flag is set.

This module requires DB_File and Storable.


Lincoln Stein <>


Please direct usage questions or support issues to the mailing list:

rather than to the module maintainer directly. Many experienced and reponsive experts will be able look at the problem and quickly address it. Please include a thorough description of the problem with code and data examples if at all possible.

Reporting Bugs

Report bugs to the Bioperl bug tracking system to help us keep track the bugs and their resolution. Bug reports can be submitted via the web:


The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _


 Title   : new
 Usage   : $db = Bio::DB::FileCache->new(
                 -seqdb => $db,   # Bio::DB::RandomAccessI database
                 -file  => $path, # path to index file
                 -keep  => $flag, # don't unlink index file
 Function: creates a new on-disk cache
 Returns : a Bio::DB::RandomAccessI database
 Args    : as above
 Throws  : "Must be a randomaccess database" exception
           "Could not open primary index file" exception

If no index file is specified, will create a temporary file in your system's temporary file directory. The name of this temporary file can be retrieved using file_name().


 Title   : get_Seq_by_id
 Usage   : $seq = $db->get_Seq_by_id('ROA1_HUMAN')
 Function: Gets a Bio::Seq object by its name
 Returns : a Bio::Seq object
 Args    : the id (as a string) of a sequence
 Throws  : "id does not exist" exception


 Title   : get_Seq_by_acc
 Usage   : $seq = $db->get_Seq_by_acc('X77802');
 Function: Gets a Bio::Seq object by accession number
 Returns : A Bio::Seq object
 Args    : accession number (as a string)
 Throws  : "acc does not exist" exception


 Title   : seqdb
 Usage   : $seqdb = $db->seqdb([$seqdb])
 Function: gets/sets the Bio::DB::RandomAccessI database
 Returns : a Bio::DB::RandomAccessI database
 Args    : new sequence database (optional)
 Throws  : nothing


 Title   : file_name
 Usage   : $path = $db->file_name([$file_name])
 Function: gets/sets the name of the cache file
 Returns : a path
 Args    : new cache file name (optional)
 Throws  : nothing

It probably isn't useful to set the cache file name after you've opened it.


 Title   : keep
 Usage   : $keep = $db->keep([$flag])
 Function: gets/sets the value of the "keep" flag
 Returns : current value
 Args    : new value (optional)
 Throws  : nothing

The keep flag will cause the index file to be unlinked when the process exits. Since on some operating systems (Unix, OS/2) the unlinking occurs during the new() call immediately after opening the file, it probably isn't safe to change this value.


 Title   : db
 Usage   : $db->db
 Function: returns tied hash to index database
 Returns : a Berkeley DB tied hashref
 Args    : none
 Throws  : nothing


 Title   : flush
 Usage   : $db->flush
 Function: flushes the cache
 Returns : nothing
 Args    : none
 Throws  : nothing


 Title   : get_Seq_by_version
 Usage   : $seq = $db->get_Seq_by_version('X77802.1');
 Function: Gets a Bio::Seq object by sequence version
 Returns : A Bio::Seq object
 Args    : accession.version (as a string)
 Throws  : "acc.version does not exist" exception