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, the method comprising: 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 positional delta tree provided as a write-store structure established within a memory store accessible by said update processor, and wherein said positional delta tree stores said differential update in a manner to identify an update tuple data position within said database table; 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 using the positional delta tree and the position of tuple data read from said database table; and determining, to transfer said differential update from the transaction positional delta tree to a write positional delta tree, wherein said determining step is conditional dependent on whether the differential update conflicts with another differential update transferred to said write positional delta tree.