[Problem to be solved] It is an object in one aspect of an embodiment of the invention to suppress narrow down noise generated when targets are narrowed down at the time of a string search performed on document data.
[Solution] According to an aspect of an embodiment, a computer changes, in accordance with whether a document element that has a predetermined number of child elements is present in a document file, control of determining whether data in the document file is to be included in which of a plurality of blocks by changing the control between the control performed for each document element in the hierarchy of the child elements and the control performed for each document element in the hierarchy of the document element or in the hierarchy higher than the hierarchy of the document element; divides the document file into the plurality of blocks; and generates, for each piece of data obtained by being divided, index information that indicates whether each of the pieces of the data includes predetermined character information.