Patent ID: 11899661
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Computer technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 10:
11. An extraction apparatus configured to optimize multiple queries and reduce a time to extract a common plan subtree that is a common part among a plurality of plan trees corresponding to the multiple queries by avoiding use of acyclic graphs, the extraction apparatus comprising:
first assignment circuitry configured to calculate, based on pieces of information of nodes of a plan tree of the plurality of plan trees, a hash value for each of the nodes to assign the calculated hash value to the corresponding each of the nodes;
second assignment circuitry configured to assign a unique number different from the hash value and associated with a set of pointers to each of the nodes based on the hash value of each of the nodes; and
extraction circuitry configured to list subtrees below a node of the nodes having a same unique number in an associative array indexed by hash value, to extract the common plan subtree from the plurality of plan trees.