lowercase when looking up self referential foreign key columns (#2437)

Author: jycor

enginetest/queries/foreign_key_queries.go

@@ -1640,6 +1640,82 @@ var ForeignKeyTests = []ScriptTest{
 			},
 		},
 	},
+	{
+		Name: "Self-referential foreign key is not case sensitive",
+		SetUpScript: []string{
+			"create table t1 (i int primary key, J int, constraint fk1 foreign key (J) references t1(i));",
+			"create table t2 (I int primary key, j int, constraint fk2 foreign key (j) references t2(I));",
+			"create table t3 (i int primary key, j int, constraint fk3 foreign key (J) references t3(I));",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				// Casing is preserved in show create table statements
+				Query: "show create table t1;",
+				Expected: []sql.Row{
+					{"t1", "CREATE TABLE `t1` (\n" +
+						"  `i` int NOT NULL,\n  `J` int,\n" +
+						"  PRIMARY KEY (`i`),\n" +
+						"  KEY `J` (`J`),\n" +
+						"  CONSTRAINT `fk1` FOREIGN KEY (`J`) REFERENCES `t1` (`i`)\n" +
+						") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"},
+				},
+			},
+			{
+				Query: "insert into t1 values (1, 1);",
+				Expected: []sql.Row{
+					{types.NewOkResult(1)},
+				},
+			},
+			{
+				Query:       "insert into t1 values (2, 3);",
+				ExpectedErr: sql.ErrForeignKeyChildViolation,
+			},
+			{
+				// Casing is preserved in show create table statements
+				Query: "show create table t2;",
+				Expected: []sql.Row{
+					{"t2", "CREATE TABLE `t2` (\n" +
+						"  `I` int NOT NULL,\n" +
+						"  `j` int,\n" +
+						"  PRIMARY KEY (`I`),\n" +
+						"  KEY `j` (`j`),\n" +
+						"  CONSTRAINT `fk2` FOREIGN KEY (`j`) REFERENCES `t2` (`I`)\n" +
+						") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"},
+				},
+			},
+			{
+				Query: "insert into t2 values (1, 1);",
+				Expected: []sql.Row{
+					{types.NewOkResult(1)},
+				},
+			},
+			{
+				Query:       "insert into t2 values (2, 3);",
+				ExpectedErr: sql.ErrForeignKeyChildViolation,
+			},
+			{
+				Query: "show create table t3;",
+				Expected: []sql.Row{
+					{"t3", "CREATE TABLE `t3` (\n" +
+						"  `i` int NOT NULL,\n  `j` int,\n" +
+						"  PRIMARY KEY (`i`),\n" +
+						"  KEY `j` (`j`),\n" +
+						"  CONSTRAINT `fk3` FOREIGN KEY (`j`) REFERENCES `t3` (`i`)\n" +
+						") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin"},
+				},
+			},
+			{
+				Query: "insert into t3 values (1, 1);",
+				Expected: []sql.Row{
+					{types.NewOkResult(1)},
+				},
+			},
+			{
+				Query:       "insert into t3 values (2, 3);",
+				ExpectedErr: sql.ErrForeignKeyChildViolation,
+			},
+		},
+	},
 	{
 		Name: "Cascaded DELETE becomes cascading UPDATE after first child, using ON DELETE for second child",
 		SetUpScript: []string{

sql/plan/foreign_key_editor.go

@@ -395,8 +395,8 @@ func (reference *ForeignKeyReferenceHandler) CheckReference(ctx *sql.Context, ro
 	if reference.ForeignKey.IsSelfReferential() {
 		allMatch := true
 		for i := range reference.ForeignKey.Columns {
-			colPos := reference.SelfCols[reference.ForeignKey.Columns[i]]
-			refPos := reference.SelfCols[reference.ForeignKey.ParentColumns[i]]
+			colPos := reference.SelfCols[strings.ToLower(reference.ForeignKey.Columns[i])]
+			refPos := reference.SelfCols[strings.ToLower(reference.ForeignKey.ParentColumns[i])]
 			cmp, err := reference.RowMapper.SourceSch[colPos].Type.Compare(row[colPos], row[refPos])
 			if err != nil {
 				return err