make equals in antijoins from not exists null safe

Author: angelamayxie

sql/analyzer/unnest_exists_subqueries.go

@@ -209,6 +209,15 @@ func unnestExistSubqueries(ctx *sql.Context, scope *plan.Scope, a *Analyzer, fil
 
 		switch joinType {
 		case plan.JoinTypeAnti:
+			outerFilters, _, err = transform.Exprs(outerFilters, func(e sql.Expression) (sql.Expression, transform.TreeIdentity, error) {
+				if equals, ok := e.(*expression.Equals); ok {
+					return equals.MakeNullSafe(), transform.NewTree, nil
+				}
+				return e, transform.SameTree, nil
+			})
+			if err != nil {
+				return nil, transform.SameTree, err
+			}
 			ret = plan.NewAntiJoin(ret, s.inner, expression.JoinAnd(outerFilters...)).WithComment(comment)
 			qFlags.Set(sql.QFlagInnerJoin)
 		case plan.JoinTypeSemi:

sql/expression/comparison.go

@@ -408,6 +408,11 @@ func (e *Equals) ToComparer() (Comparer, error) {
 	return e, nil
 }
 
+// MakeNullSafe returns a new NullSafeEquals with the same children
+func (e *Equals) MakeNullSafe() *NullSafeEquals {
+	return NewNullSafeEquals(e.LeftChild, e.RightChild)
+}
+
 // NullSafeEquals is a comparison that checks an expression is equal to
 // another, where NULLs do not coalesce to NULL and two NULLs compare equal to
 // each other.