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Sat, 28 Jul 2007
Lightweight Database Strategies for Perl
I don't know why. I tried giving the class a snappier title, but that didn't help. I'm really bad at titles. Maybe people are embarrassed to think about all the lightweight data storage hackery they do in Perl, and feel that they "should" be using a relational database, and don't want to commit more resources to lightweight database techniques. Or maybe they just don't think there is very much to know about it.
But there is a lot to know; with a little bit of technique you can postpone the day when you need to go to an RDB, often for quite a long time, and often forever. Many of the techniques fall into the why-didn't-I-think-of-that category, stuff that isn't too weird to write or maintain, but that you might not have thought to try.
I think it's a good class, but since it never sold well, I've decided it would do more good (for me and for everyone else) if I just gave away the materials for free.
Table of ContentsThe class is in three sections. The first section is about using plain text files and talks about a bunch of useful techniques, such as how to do binary search on sorted text files (this is nontrivial) and how to replace records in-place, when they might not fit.
The second section is about the Tie::File module, which associates a flat text file with a Perl array.
The third section is about DBM files, with a comparison of the five major implementations. It finishes up with a discussion of some of Berkeley DB's lesser-known useful features, such as its DB_BTREE file type, which offers fast access like a hash but keeps the records in sorted order