Abstract: Some embodiments of the disclosure provides a substrate for optical fiber array and the disclosed substrate fixes the fiber by epoxy. In some embodiments, the substrate includes a main body, a first holding groove, and a second holding groove. The first holding groove is notched along a width direction of the main body for holding a stripped optical fiber by epoxy. The second holding groove is an arc-shaped groove and connected with the first holding groove. The second holding groove extends along a notching direction of the first holding groove for holding an unstripped optical fiber. In other embodiments, a groove is notched along a length direction of the main body to prevent epoxy overflow.

Abstract: An index building, querying method, device and system for distributed columnar database are provided. The index building method for distributed columnar database includes: obtaining a column field from a distributed columnar database, generating a column index file in which the column field is a key word, the column index file comprising the mapping relationship between the value of the column field in the distributed columnar database and the corresponding Row field value; storing the column index file to a index catalogue corresponding to the column field in the distributed columnar database.