The main entry methods in the query subsystem transfer ownership of heap-allocated objects through raw pointers, which is error-prone. These methods should use std::unique_ptr instead. Partial list follows:

• CanonicalQuery::canonicalize(). Caller receives ownership of a CanonicalQuery.
• LiteParsedQuery::make(). Caller receives ownership of a LiteParsedQuery.
• StatusWithMatchExpression replace MatchExpression* with unique_ptr<MatchExpression>
• MatchExpression::shallowClone(). Caller receives ownership of a MatchExpression.
• PlanExecutor::make(). Caller releases ownership of a WorkingSet, a PlanStage, a CanonicalQuery and a QuerySolution, and receives ownership of a PlanExecutor.
• getExecutor(). Caller releases ownership of a CanonicalQuery, and receives ownership of a PlanExecutor (other public methods in get_executor.cpp can follow suit).
• PlanExecutor::getStats(). Caller receives ownership of a PlanStageStats.

Linking a few tickets describing ownership-related memory leaks induced by incorrect use of the above (and related) methods.