planner: fix extract correlated column for expand in building phase will panic.

pkg/planner/core/logical_expand.go

@@ -144,6 +144,15 @@ func (p *LogicalExpand) ExhaustPhysicalPlans(prop *property.PhysicalProperty) ([
 
 // ExtractCorrelatedCols implements base.LogicalPlan.<15th> interface.
 func (p *LogicalExpand) ExtractCorrelatedCols() []*expression.CorrelatedColumn {
+	// if p.LevelExprs is nil, it means the GenLevelProjections has not been called yet,
+	// which is done in logical optimizing phase. While for building correlated subquery
+	// plan, the ExtractCorrelatedCols will be called once after building, so we should
+	// distinguish the case here.
+	if p.LevelExprs == nil {
+		// since level projections generation don't produce any correlated columns, just
+		// return nil.
+		return nil
+	}
 	corCols := make([]*expression.CorrelatedColumn, 0, len(p.LevelExprs[0]))
 	for _, lExpr := range p.LevelExprs {
 		for _, expr := range lExpr {

tests/integrationtest/r/executor/expand.result

@@ -300,3 +300,26 @@ GROUP BY product WITH ROLLUP) AS tmp
 WHERE product is null;
 product	SUM
 NULL	7785
+
+SELECT product FROM t1 WHERE EXISTS
+(SELECT product, country_id , SUM(profit) FROM t1 AS t2
+WHERE t1.product=t2.product GROUP BY product, country_id WITH ROLLUP
+HAVING SUM(profit) > 6000);
+product
+Computer
+Computer
+Computer
+Computer
+Computer
+
+SELECT product, country_id , year, SUM(profit) FROM t1
+GROUP BY product, country_id, year HAVING country_id is NULL;
+product	country_id	year	SUM(profit)
+SELECT CONCAT(':',product,':'), SUM(profit), AVG(profit) FROM t1
+GROUP BY product WITH ROLLUP;
+CONCAT(':',product,':')	SUM(profit)	AVG(profit)
+NULL	7785	519.0000
+:TV:	600	120.0000
+:Calculator:	275	68.7500
+:Phone:	10	10.0000
+:Computer:	6900	1380.0000

tests/integrationtest/t/executor/expand.test

@@ -131,3 +131,22 @@ t1.country_id=t2.country_id GROUP BY product, country, year WITH ROLLUP;
 SELECT product, `SUM` FROM (SELECT product, SUM(profit) AS 'sum' FROM t1
                             GROUP BY product WITH ROLLUP) AS tmp
 WHERE product is null;
+
+--echo
+--sorted_result
+SELECT product FROM t1 WHERE EXISTS
+(SELECT product, country_id , SUM(profit) FROM t1 AS t2
+ WHERE t1.product=t2.product GROUP BY product, country_id WITH ROLLUP
+ HAVING SUM(profit) > 6000);
+
+--echo
+--sorted_result
+# The following does not return the expected answer, but this is a limitation
+# in the implementation so we should just document it
+SELECT product, country_id , year, SUM(profit) FROM t1
+GROUP BY product, country_id, year HAVING country_id is NULL;
+
+--echo
+--sorted_result
+SELECT CONCAT(':',product,':'), SUM(profit), AVG(profit) FROM t1
+GROUP BY product WITH ROLLUP;