Speeding up heterogeneous data access by converting and pushing down string comparisons
W. Zhang, Per-Åke Larson · 1999
Pushing down predicates to an external data source is critical to the performance for querying heterogeneous data sources. However, predicate-containing string comparisons cannot be pushed down unchanged if the external data source uses a different collating sequence. We describe a table-driven technique for rewriting such predicates to account for the differences in collation. In addition to precise conversion, we also consider imprecise conversion.