4. A search system, comprising: a first search index that is used to carry out an index search in response to a search request; a second search index that is used to reflect first updated documents; a first updating candidate document storage device that stores data of second updated documents since a reflection processing of said first updated documents against said second search index began; a second updating candidate document storage device that stores data of said first updated documents used for said reflection processing against said second search index; a first document ID manager, for added or modified document, that is used in search and stores document IDs of said first updated documents; a first pattern matching document storage device that stores said data of said first updated documents for a character string pattern matching in said search; a second document ID manager, for added or modified document, that stores document IDs of said second updated documents since said reflection processing of said first updated documents against said second search index began; a second pattern matching document storage device that stores said data of said second updated documents since said reflection processing of said first updated documents against said second search index began; an index search controller; and a string pattern matching controller, and wherein, when said reflection processing of said first updated documents against said second search index is completed, said index search controller to use said second search index after said reflection processing as said first search index by switching, said index search controller to move said data of said second updated documents, which is stored in said first updating candidate document storage device, to said second updating candidate document storage device by overwriting, said string pattern matching controller to move said document IDs of said second updated documents, which are stored in said second document ID manager, to said first document ID manager by overwriting, and said string pattern matching controller to move said data of said second updated documents, which is stored in said second pattern matching document storage device, to said first pattern matching document storage device by overwriting.
4. A search system, comprising: a first search index that is used to carry out an index search in response to a search request; a second search index that is used to reflect first updated documents; a first updating candidate document storage device that stores data of second updated documents since a reflection processing of said first updated documents against said second search index began; a second updating candidate document storage device that stores data of said first updated documents used for said reflection processing against said second search index; a first document ID manager, for added or modified document, that is used in search and stores document IDs of said first updated documents; a first pattern matching document storage device that stores said data of said first updated documents for a character string pattern matching in said search; a second document ID manager, for added or modified document, that stores document IDs of said second updated documents since said reflection processing of said first updated documents against said second search index began; a second pattern matching document storage device that stores said data of said second updated documents since said reflection processing of said first updated documents against said second search index began; an index search controller; and a string pattern matching controller, and wherein, when said reflection processing of said first updated documents against said second search index is completed, said index search controller to use said second search index after said reflection processing as said first search index by switching, said index search controller to move said data of said second updated documents, which is stored in said first updating candidate document storage device, to said second updating candidate document storage device by overwriting, said string pattern matching controller to move said document IDs of said second updated documents, which are stored in said second document ID manager, to said first document ID manager by overwriting, and said string pattern matching controller to move said data of said second updated documents, which is stored in said second pattern matching document storage device, to said first pattern matching document storage device by overwriting. 7. The search system as set forth in claim 4 , further comprising: an index search processor to carry out an index search for said first search index in response to a search request; a pattern matching processor to carry out a character string matching for said first pattern matching document storage device; and a controller, and wherein said index search processor to carry out said index search relating to said search request by using said first search index to obtain a first list of document IDs of pertinent documents, said pattern matching processor to carry out said string pattern matching relating to said search request for said first pattern matching document storage device to obtain a second list of document IDs of pertinent documents, and said controller to remove from said first list, document IDs of documents updated after generation of said first search index, to generate a third list of document IDs obtained by the removing, to generate a sum-set of said second list and said third list, and to output a search result including said sum-set of said second list and said third list.