Added test.

tests/queries/0_stateless/01515_mv_and_array_join_optimisation_bag.sql

+CREATE TABLE visits
+(
+    `CounterID` UInt32,
+    `StartDate` Date,
+    `StartTime` DateTime,
+    `GoalsID` Array(UInt32),
+    `Sign` Int8
+)
+ENGINE = Null;
+
+
+CREATE MATERIALIZED VIEW goal_view TO goal
+(
+    `CounterID` UInt32,
+    `StartDate` Date,
+    `GoalID` UInt32,
+    `Visits` AggregateFunction(sumIf, Int8, UInt8),
+    `GoalReaches` AggregateFunction(sum, Int8)
+) AS
+SELECT
+    CounterID,
+    StartDate,
+    GoalID,
+    sumIfState(Sign, _uniq = 1) AS Visits,
+    sumState(Sign) AS GoalReaches
+FROM visits
+ARRAY JOIN 
+    GoalsID AS GoalID,
+    arrayEnumerateUniq(GoalsID) AS _uniq
+GROUP BY 
+    CounterID,
+    StartDate,
+    GoalID
+ORDER BY 
+    CounterID ASC,
+    StartDate ASC,
+    GoalID ASC;
+
+CREATE TABLE goal
+(
+     `CounterID` UInt32,
+     `StartDate` Date,
+     `GoalID` UInt32,
+     `Visits` AggregateFunction(sumIf, Int8, UInt8),
+     `GoalReaches` AggregateFunction(sum, Int8)
+) ENGINE = AggregatingMergeTree PARTITION BY toStartOfMonth(StartDate) ORDER BY (CounterID, StartDate, GoalID) SETTINGS index_granularity = 256;
+
+INSERT INTO visits (`CounterID`,`StartDate`,`StartTime`,`Sign`,`GoalsID`) VALUES (1, toDate('2000-01-01'), toDateTime(toDate('2000-01-01')), 1, [1]);