B-Tree Indexes

As explained in the Indexes page, the eXtremeDB, B-Tree (tree) indexes can include any combination of fields, structure elements or vector elements from a given class. Tree indexes can be used for ordered (sorted) retrieval, range retrieval and pattern matching.

Also, key-value-inclusive and covering indexes can be used with tree indexes to provide significant performance improvements by including the desired data field(s) in the index. Please use this link for further details.

Memory Consumption

Memory consumption is comparable for tree and hash indexes of transient classes. A rough estimate for a tree index is 10 bytes per entry (exact size depends on the order of insertions or deletions); and H + 8 bytes per entry for a hash index, where the constant H is fixed size space taken by the hash table and can be calculated as E / 5 * 4 where E is the estimated number of hash entries provided by you in the database schema and 5 is a constant hash factor used by eXtremeDB. If reallocation of the hash table is necessary, then the size will be H * 2.