org.apache.spark.sql.catalyst.optimizer
PushProjectionThroughUnion
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package optimizer
Returns true if expr can be evaluated using only the output of plan.
Returns true if expr can be evaluated using only the output of plan. This method
can be used to determine when it is acceptable to move expression evaluation within a query
plan.
For example consider a join between two relations R(a, b) and S(c, d).
- canEvaluate(EqualTo(a,b), R) returns true
- canEvaluate(EqualTo(a,c), R) returns false
- canEvaluate(Literal(1), R) returns true as literals CAN be evaluated on any plan
Returns true iff expr could be evaluated as a condition within join.
Returns true iff expr could be evaluated as a condition within join.
Name for this rule, automatically inferred based on class name.
Name for this rule, automatically inferred based on class name.
Pushes Project operator to both sides of a Union operator. Operations that are safe to pushdown are listed as follows. Union: Right now, Union means UNION ALL, which does not de-duplicate rows. So, it is safe to pushdown Filters and Projections through it. Filter pushdown is handled by another rule PushDownPredicate. Once we add UNION DISTINCT, we will not be able to pushdown Projections.