4. The non-transitory computer-readable recording medium according to claim 3 , wherein the process further includes: performing control such that the referring of the presence information and the searching of the other compression dictionary are executed earlier than the referring of the order information; and suppressing the referring of the order information when the presence information indicates that any of the character strings included in the other compression dictionary does not include the certain character information at the middle position of the certain character string or when it was not possible to specify the compression target character string by searching the other compression dictionary.
4. The non-transitory computer-readable recording medium according to claim 3 , wherein the process further includes: performing control such that the referring of the presence information and the searching of the other compression dictionary are executed earlier than the referring of the order information; and suppressing the referring of the order information when the presence information indicates that any of the character strings included in the other compression dictionary does not include the certain character information at the middle position of the certain character string or when it was not possible to specify the compression target character string by searching the other compression dictionary. 6. The non-transitory computer-readable recording medium according to claim 4 , wherein the performing control includes performing control such that referring of another order information indicating whether one or more of the concatenated character strings included in the compression dictionary include the compression target character string at a certain position in the concatenated character string is performed earlier than the searching of the other compression dictionary when the presence information indicates that one or more of the character strings included in the other compression dictionary include the certain character information at the certain position in the character string.