When doing an UPDATE or DELETE using a multi-column index where only a few

When doing an UPDATE or DELETE using a multi-column index where only a few
of the earlier columns of the index are useful for the index lookup,
postpone doing the main table seek until after all WHERE clause constraints
have been evaluated, in case those constraints can be covered by unused
later terms of the index, thus avoiding unnecessary main table seeks.

FossilOrigin-Name: 7fee0b1075d622835dc6828c061be516102da9e2809f52d9ab7c4bbef7dfb871