Masking Conceptual Schema Changes

• The replacement of Contracts by LargeContracts and SmallContracts can be masked by the view.

• However, queries with the condition val� must be asked wrt LargeContracts for efficient execution: so users concerned with performance have to be aware of the change.

CREATE VIEW Contracts(cid, sid, jid, did, pid, qty, val)

AS SELECT *

FROM LargeContracts

UNION

SELECT *

FROM SmallContracts

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