A really simple SQL database.

A good way to understand the system is to start from the lowest level layers and build your way up from there. The layers are listed here in that order:

• file - read pages from disk and write them back to disk
• log - read and write log records
• buffer - maintain a cache of frequently accessed pages
• tx.recovery - provide durability for changes
• tx.concurrency - implement locking needed to guarantee atomicity for changes
• tx - tie recovery and concurrency properties together
• record - provide structure on top of raw pages to represent database records
• metadata - maintain metadata about structure of different database objects
• query - queries and query plans expressed in relational algebra
• parse - parsing SQL statements
• planner - translate parsed SQL trees into relational algebra
• jdbc - JDBC wrapper on top of everything else

The implementation takes heavy inspiration from Edward Sciore's SimpleDB, augmented by implementations of various exercises in his textbook Database Design and Implementation.