Optimizer Directives

A then B

Seq A, Seq B Cost:100

Seq A, Idx B Cost:50

Idx A, Idx B Cost:20

etc.

B then A

Seq B, Seq A Cost:100

Seq B, Idx A Cost:50

Idx B, Idx A Cost:10

etc.

Select --ORDERED

* from A, B

where A.join_col = B.join_col

With the directive, ORDERED, the optimizer only considers paths that read from A then B.

The lowest cost is then chosen from those paths.

Normally, this path

would be chosen

With the directive,

this path would be chosen

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