| 摘要 |
PURPOSE:To read ahead data blocks efficiently with only slight increase of the number of input buffers by merging m-number of input files having sorted data strings to generate one file. CONSTITUTION:When the control is transferred to a merger 32 from a merge control part 38, the merger 32 compares data in input buffers 21-24 with one another from the start of each buffer to perform the merge processing in a certain order, for example, the ascending order in accordance with a certain key and writes results in an output buffer 33 successively. When data in one buffer runs out, it is reported to the merge control part 38. When detecting the buffer which should be empty first, a look ahead control part 36 instructs a reader 15 to read the next block from an input file corresponding to this buffer. The reader 15 reads ahead the next merge object block from an input file 11 and inputs it to, for example, the input buffer 24. This look ahead input operation is performed in parallel with the merge processing of said merger 32. |
