gem install rspec for tests
B+ trees stores data ONLY on leaves, unlike B-trees.
1 page = 1 B+-tree node
(1st node in an empty tree is initialized as a root leaf node)
internal nodes store children as page indices (rather than e.g. pointers)
a Pager manages pages. accessing data should be done through it (get_page) so it can handle loading from disk.
a Cursor uniquely identifies a page and a cell within it. they are not a singleton and may be instanced
a Table contains a pager and the position of the root node. it does not contain a schema as that is both global (memory offsets) and described by Row (this is probably prone to change if this database is ever actually used)
order (n. of cells) of internal nodes >= order of leaf nodes (because we're just cramming as much as we can, and leaf nodes' cells are bigger than internal nodes', so we have to fit less)
meta commands:
- .exit
- .btree # print data tree structure
- .print # print constants
commands:
- insert %field1% %field2% %fieldn%
- select