This disclosure relates to bitmap index writing, dumping, merging, and querying. In one aspect, a method includes determining, based on update data, a to-be-updated row of a bitmap index that indexes data of a database using a bitmap data structure. The to-be-updated row of the bitmap index is locked. The locking includes adding a row lock to the to-be-updated row, thereby preventing the to-be-updated row from being updated by other update operations. At least one other row of the bitmap index remains unlocked for updating by other update operations. Data in the to-be-updated row of the bitmap index is updated based on the update data.