Hi Jonathan,
On Jan 26, 2005, at 11:01, Lynch, Jonathan wrote:
Still - how do database programs do it? Is each record a separate file or something? If it were possible to use a single stack as a huge database, it would be very convenient.
The big problem of course is that opening a stack loads the entire thing into memory. With a real database, certain data-structures are maintained in memory -- and the sizes of those are usually tunable for performance -- but the database files are not all loaded into memory at once. For the most part each record is not a separate file. What is typically done is something like this: The database files maintain an internal fixed block size. When records are written to the file they can span multiple, discontinuous blocks. The blocks for deleted records can be reclaimed and reused by new or updated records. Indexes are maintained (sometimes in separate files, sometimes in the same file) that allow for fast lookup of records in the database.
--gordon
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