Lightweight Databases

Ordered Hashes

DB_File actually supports three different file types

     tie %hash,  'DB_File', $file, O_CREAT|O_RDWR, 0666, $DB_HASH;
     tie %hash,  'DB_File', $file, O_CREAT|O_RDWR, 0666, $DB_BTREE;
     tie @array, 'DB_File', $file, O_CREAT|O_RDWR, 0666, $DB_RECNO;

The default is DB_HASH which we've seen already
DB_RECNO associates a plain text file with an array
- But Tie::File may be preferable, for a number of reasons
- (See the handout)
DB_BTREE uses a different data structure called a B-tree
- Also called a VSAM file by big-iron types
- Unlike a hash, it keeps the records in order
- For very large databases (1,000,000 records) lookup may be slower than hashes