Patent ID: 7941413

Claim:
An index processing method for inserting a key into an index of a tree structure, the key indicating a respective value for a specific item of data newly input into a computer, the tree structure including a plurality of keys respectively indicating recorded values for the specific item of data successively input and nodes for storing the keys, the index being used for searching for the item of data associated with the key, the index processing method comprising: identifying a node in the tree structure to which the key is to be inserted; determining whether a quantity of keys stored in the identified node exceeds a predetermined key storage upper limit; and upon determining that the quantity of keys stored in the identified node exceeds the key storage upper limit, splitting the identified node into a first node and a second node according to a node split ratio that is controlled using a ratio changing process that changes the node split ratio, wherein the ratio changing process comprises determining a key tendency representing a characteristic of value change for the specific item of data, and determining the node split ratio based on the key tendency.