1. A method of operating a database engine as executed on a host computer system, wherein said database engine is responsive to database requests received with respect to database tables stored by persistent data stores accessible by said database engine, said method comprising the steps: a) responding, by a update processor, to update requests to store update tuple data with respect to a database table, wherein said update processor operates to store said update tuple data as a differential update in a write positional delta tree provided as a write-store structure established within a memory store accessible by said update processor, and wherein said write positional delta tree stores said differential update in a manner pre-computed to identify an update tuple data position within said database table; b) responding, by a query processor, to query requests to provide responsive tuple data, with respect to said database table, wherein said query processor operates to dynamically merge said differential update with tuple data retrieved from said database table based on the pre-computed position of said differential update and the position of tuple data read from said database table.