NAME

VCP::DB_File::big_records - VCP::DB_File::sdbml subclass for large records

SYNOPSIS

    use VCP::DB_File;
    VCP::DB_File->new;

DESCRIPTION

sdbm files are limited to 1008 bytes per record, including key. That's just not enough for storing revisions in (although it suffices for most other VCP needs).

This subclass assumes your disk is large enough and that you won't be altering records in place, but allows for unlimited record sizes. No attempt is made to reclaim free space; so far our application doesn't need that.

Records are retrievable in the order they were added in (so this "file" may be a queue) or in random order (like a DB file).

INTERNALS

There are three related data sets:

    - an sdbm database "db", which is an index to the location and size
      of each record for the key of the record
    - a file "records.mdb", which is a set of ( key, record size, record data)
      entries for each record
    - a file "order.txt", which is a flat file with one key per record
      in the order that they were added to the file

Generally, you should use this module only to read or write a dataset as an error in reading could cause corruption if you write (the orders.txt is not flushed or seek() properly on a read error). This is sufficient for our purposes, because these files are only used by but could be a problem if read/write mode is needed.

foreach_record_do

    $db->foreach_record_do( sub { ... } );

Iterate over the contents in as-stored order, executing sub { ... } for each one found.

dump

BROKEN FOR NOW. Reports the pointers, not the pointed-to data

TODO: fix.

LIMITATIONS

There is no way (yet) of telling the mapper to continue processing the rules list. We could implement labels like " << label"> > to be allowed before pattern expressions (but not between pattern and result), and we could then impelement " <<goto label"> >. And a " <<next"> > could be used to fall through to the next label. All of which is wonderful, but I want to gain some real world experience with the current system and find a use case for gotos and fallthroughs before I implement them. This comment is here to solicit feedback :).

AUTHOR

Barrie Slaymaker <barries@slaysys.com>

COPYRIGHT

See VCP::License ("vcp help license") for the terms of use.

POD ERRORS

Hey! The above document had some coding errors, which are explained below:

Around line 42:: You can't have =items (as at line 237) unless the first thing after the =over is an =item