WL#3686: Avoid read before PK/UK update/deletes without expressions
Affects: Server-6.0 — Status: Code-Review
When performing a primary key or unique key update it is almost never necessary to read the record before the update. The exception to this is when the primary key is updated since then a delete followed by an insert is required and this must be prepared by reading the record. It's especially easy to implement this for primary key or unique key updates where the readset is empty where only constants are assigned to the fields. For DBT2 this will remove around 8 primary key lookups per transaction so it's a very significant performance improvement.
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