Abstract: The processing of transaction oriented data tends to be row-oriented, while the processing of analytical operations tends to be column-oriented. Various systems, sometimes referred to as operational data warehouses, may comprise mechanisms adapted for use in scenarios where both transactional data processing and analytical queries are to be performed efficiently. The operational data warehouse (ODW) may perform and update data efficiently by maintaining a table in structures comprising a column store, a delta store, a delete bitmap, and a delete buffer. In this environment, key values may be associated for each row such that the ODW may more efficiently seek rows. Further, rows may also be excluded from a column store based at least in part on a filter criterion. The filtering criterion may be used to filter out rows based on a created predicate set by a user or the system.

Abstract: Currency and consistency requirements are specified as part of a query against a database that may contain replicated data that is updated asynchronously and therefore may not be completely up to date. The database system constructs query execution plans that include an input selection operator that verifies the currency of a replica and selects a subplan using the replica for execution only when the replica meets the query's currency constraints. It checks possible query execution plans at construction time against the query's consistency constraints and any plans that may produce a result not meeting the consistency constraints are rejected. In this way, the query result is guaranteed to satisfy the query's currency and consistency requirements.