Package org.apache.derby.impl.store.access.btree.index

Implements classes used by the language layer to implement SQL secondary indexes.

See: Description

Class Summary

Class	Description
B2I	Implements an instance of a B-Tree secondary index conglomerate.
B2I_10_3	Class used to instantiate 10.3 version of the B2I object.
B2I_v10_2	Class used to instantiate 10.2 version of the B2I object.
B2IController	Controller used to insert rows into a secondary index.
B2ICostController	Controller used to provide cost estimates to optimizer about secondary index data access.
B2IFactory	The "B2I" (acronym for b-tree secondary index) factory manages b-tree conglomerates implemented on the raw store which are used as secondary indexes.
B2IForwardScan	The btree secondary index implementation of ScanManager which provides reading and deleting of entries in the btree secondary index.
B2IMaxScan	Scan used to find maximum value in the secondary index.
B2INoLocking	Secondary index locking policy that does no locking.
B2IStaticCompiledInfo	This class implements the static compiled information relevant to a btree secondary index.
B2IUndo	The B2IUndo interface packages up the routines which the rawstore needs to call to perform logical undo of a record in a B2i.
D_B2IController	Debugging class used to print debug information about a B2I.

Package org.apache.derby.impl.store.access.btree.index Description

Implements classes used by the language layer to implement SQL secondary indexes. The classes here extend and use the classes in org.apache.derby.impl.store.access.btree to implement a locked btree index.

The key to understanding the class layout is to understand the public store interfaces in org.apache.derby.iapi.store.access.conglomerate, which contains the shared interfaces that must be implemented by all access methods. Currently Derby implements heap and btree index access methods. Users of access methods use the same interface no matter what the underlying type or particular implementation of the access method. Therefore, Derby can support multiple types of btree index implementations, which if done right should require no changes to actual users of the access methods.

In reality the interfaces would have to change in some ways to support a radically different kind of access method, such as GiST. But the implementor should enhance the interfaces in the conglomerate package so that these can then be supported by all existing access methods.

Isolation Levels

Isolation level implementation in the B-Tree index is done with data only locking, i.e., locks on secondary index rows are actually locks on the data rows that they point to. The specifics of particular isolation levels are hidden in various implementations of the BTreeLockingPolicy class. The classes which do scans, deletes, and inserts do not have isolation specific code, instead they make lock calls using BTreeLockingPolicy interfaces, and then depending on the isolation level one of the implmentations does the actual locking.