New access index for fast execution of conjunctive queries over text data

Complex queries with multiple conjunctive (AND) predicates have attracted increasing attention for their importance in OLAP systems. The signature index is ideal for the fast execution of queries involving multiple conjunctive predicates. However, previous signature-based methods did not separate the signatures from different attributes. We have developed a signature-augmented access index, called an MG-tree. Its main features are: (1) it is a lightweight search tree for indexing multiple attributes of text data, and (2) it eliminates the mix of signatures from different attributes, so the construction and maintenance of the index is easy and searching is efficient. Our analyses and experiments show that the MG-tree achieved a significant improvement in terms of access speed and storage space overhead over both tree-like indexes and previous multi-dimensional signature indexes, and is easier to build and maintain. The MG-tree can be employed in practical DBMS implementations.