[][src]Module transform::redundant_join

Remove redundant collections of distinct elements from joins.

This analysis looks for joins in which one collection contains distinct elements, and it can be determined that the join would only restrict the results, and that the restriction is redundant (the other results would not be reduced by the join).

This type of optimization shows up often in subqueries, where distinct collections are used in decorrelation, and afterwards often distinct collections are then joined against the results.

Structs

ProvInfo

A relationship between a collections columns and some source columns.

RedundantJoin

Remove redundant collections of distinct elements from joins.