1. A computer program product for optimizing query performance in a relational database management system, the computer program product comprising a non-transitory computer readable storage medium having program code embodied therewith, the program code executable by a processor to: receive, by the processor, a query at the relational database management system; determine, by the processor, whether the query is expected to be a long-running query; in response to determining that the query is expected to be a long-running query, start, by the processor, a full table scan to fetch records needed to satisfy the query from the relational database management system; in parallel with conducting the full table scan, build, by the processor, a performance object capable of satisfying the query in the relational database management system; in response to completing the construction of the performance object prior to completing the full table scan, stop, by the processor, the full table scan and use the newly built performance object instead to satisfy the query; and store, by the processor, the performance object in one or more of: storage and memory, for a predetermined time period.
6. The computer program product of claim 1 , wherein determining whether the query is expected to be a long-running query includes: examining sources exogenous to the relational database management system, which sources are referenced by the query, to determine whether the query is expected to be long running.