|Modifier and Type||Field and Description|
The value of this query hint determines how optimistic the optimizer will be in selecting the join cardinality for its joins.
static final String OPTIMISTIC
1.0, which is the historical behavior.
For a value of
0.67 the optimizer takes a mostly
optimistic view by default - the join cardinality will be
* the MIN + 0.33 * the MAX. This settting will eliminate some
of the worst possible outcomes (ones where we guess wrong and get a
very bad join order as a result).
BSBM BI Q1 is a good example of a query that benefits from the pessimistic approach, and LUBM Q2 is a good example of a query that benefits from the optimistic approach.
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