fix nil deref on Dispose() in

Author: elianddb

enginetest/memory_engine_test.go

@@ -200,23 +200,29 @@ func TestSingleQueryPrepared(t *testing.T) {
 
 // Convenience test for debugging a single query. Unskip and set to the desired query.
 func TestSingleScript(t *testing.T) {
-	t.Skip()
+	//t.Skip()
 	var scripts = []queries.ScriptTest{
 		{
-			Name:        "AS OF propagates to nested CALLs",
-			SetUpScript: []string{},
+			// https://github.com/dolthub/dolt/issues/9987
+			Name: "GROUP BY nil pointer dereference in Dispose when Next() never called",
+			SetUpScript: []string{
+				"CREATE TABLE test_table (id INT PRIMARY KEY, value INT, category VARCHAR(50))",
+				"INSERT INTO test_table VALUES (1, 100, 'A'), (2, 200, 'B'), (3, 300, 'A')",
+			},
 			Assertions: []queries.ScriptTestAssertion{
 				{
-					Query: "create procedure create_proc() create table t (i int primary key, j int);",
-					Expected: []sql.Row{
-						{types.NewOkResult(0)},
-					},
+					// LIMIT 0 causes the iterator to close without ever calling Next() on groupByIter
+					// This leaves all buffer elements as nil, causing panic in Dispose()
+					Query:    "SELECT category, SUM(value) FROM test_table GROUP BY category LIMIT 0",
+					Expected: []sql.Row{},
 				},
 				{
-					Query: "call create_proc()",
-					Expected: []sql.Row{
-						{types.NewOkResult(0)},
-					},
+					Query:    "SELECT category, COUNT(*) FROM test_table GROUP BY category LIMIT 0",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "SELECT SUM(value) FROM test_table LIMIT 0",
+					Expected: []sql.Row{},
 				},
 			},
 		},

sql/rowexec/agg.go

@@ -103,7 +103,9 @@ func (i *groupByIter) Close(ctx *sql.Context) error {
 
 func (i *groupByIter) Dispose() {
 	for _, b := range i.buf {
-		b.Dispose()
+		if b != nil {
+			b.Dispose()
+		}
 	}
 }
 
@@ -234,7 +236,9 @@ func (i *groupByGroupingIter) Dispose() {
 		bs, _ := i.get(k)
 		if bs != nil {
 			for _, b := range bs {
-				b.Dispose()
+				if b != nil {
+					b.Dispose()
+				}
 			}
 		}
 	}