An efficient algorithm for three-component key index construction

Abstract

In this paper, proximity full-text searches in large text arrays are considered. A search query consists of several words. The search result is a list of documents containing these words. In a modern search system, documents that contain search query words that are near each other are more relevant than documents that do not share this trait. To solve this task, for each word in each indexed document, we need to store a record in the index. In this case, the query search time is proportional to the number of occurrences of the queried words in the indexed documents. Consequently, it is common for search systems to evaluate queries that contain frequently occurring words much more slowly than queries that contain less frequently occurring, ordinary words. For each word in the text, we use additional indexes to store information about nearby words at distances from the given word of less than or equal to MaxDistance, which is a parameter. This parameter can take a value of 5, 7, or even more. Three-component key indexes can be created for faster query execution. Previously, we presented the results of experiments showing that when queries contain very frequently occurring words, the average time of the query execution with three-component key indexes is 94.7 times less than that required when using ordinary inverted indexes. In the current work, we describe a new three-component key index building algorithm and demonstrate the correctness of the algorithm. We present the results of experiments creating such an index that is dependent on the value of MaxDistance.