Individual trees

class larch.tree.BTree(forest, node_store, root_id)

A balanced search tree (copy-on-write B-tree).

The tree belongs to a forest. The tree nodes are stored in an external node store; see the NodeStore class.

root_id gives the id of the root node of the tree. The root node must be unique to this tree, as it is modified in place. root_id may also be None, in which case a new node is created automatically to serve as the root node.

count_range(minkey, maxkey)

Return number of keys in range.

insert(key, value)

Insert a new key/value pair into the tree.

If the key already existed in the tree, the old value is silently forgotten.

lookup(key)

Return value corresponding to key.

If the key is not in the tree, raise KeyError.

lookup_range(minkey, maxkey)

Return list of (key, value) pairs for all keys in a range.

minkey and maxkey are included in range.

range_is_empty(minkey, maxkey)

Is a range empty in the tree?

This is faster than doing a range lookup for the same range, and checking if there are any keys returned.

remove(key)

Remove key and its associated value from tree.

If key is not in the tree, KeyValue is raised.

remove_range(minkey, maxkey)

Remove all keys in the given range.

Range is inclusive.

exception larch.tree.KeySizeMismatch(key, wanted_size)

User tried to use key of wrong size.

exception larch.tree.ValueTooLarge(value, max_size)

User tried ot use a vlaue htat is too large for a node.