18. A computer system to add data in a data structure, comprising: a computer processor to: receive an instruction to insert data into a table of an insert-only in-memory database; responsive to a determination by the computer processor that the data does not already exist in an encoding dictionary and a decoding dictionary of the data structure, add the data to each of the encoding and decoding dictionaries; assign a value identifier (valueID) for the added data in each of the encoding and decoding dictionaries, the valueID specifying a location in a table of a corresponding record; and add the valueID into an attribute vector corresponding to the encoding and decoding dictionaries in the data structure; and a memory to: store a first copy of each of the encoding dictionary and the decoding dictionary in a main store; store a second copy of each of the encoding dictionary and the decoding dictionary in a differential buffer; and store the attribute vector in an index, wherein, for each column in the table, there are separate and different encoding dictionaries, decoding dictionaries and attribute vectors.
18. A computer system to add data in a data structure, comprising: a computer processor to: receive an instruction to insert data into a table of an insert-only in-memory database; responsive to a determination by the computer processor that the data does not already exist in an encoding dictionary and a decoding dictionary of the data structure, add the data to each of the encoding and decoding dictionaries; assign a value identifier (valueID) for the added data in each of the encoding and decoding dictionaries, the valueID specifying a location in a table of a corresponding record; and add the valueID into an attribute vector corresponding to the encoding and decoding dictionaries in the data structure; and a memory to: store a first copy of each of the encoding dictionary and the decoding dictionary in a main store; store a second copy of each of the encoding dictionary and the decoding dictionary in a differential buffer; and store the attribute vector in an index, wherein, for each column in the table, there are separate and different encoding dictionaries, decoding dictionaries and attribute vectors. 19. The computer system of claim 18 , wherein the computer processor further sorts encoding dictionary by the added data.