ddl: prevent dropping in-use resource group

ddl/BUILD.bazel

@@ -80,6 +80,7 @@ go_library(
         "//parser/opcode",
         "//parser/terror",
         "//parser/types",
+        "//privilege",
         "//sessionctx",
         "//sessionctx/binloginfo",
         "//sessionctx/stmtctx",

ddl/ddl_api.go

@@ -47,6 +47,7 @@ import (
 	"github.com/pingcap/tidb/parser/mysql"
 	"github.com/pingcap/tidb/parser/terror"
 	field_types "github.com/pingcap/tidb/parser/types"
+	"github.com/pingcap/tidb/privilege"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/sessiontxn"
@@ -7668,6 +7669,17 @@ func (d *ddl) DropResourceGroup(ctx sessionctx.Context, stmt *ast.DropResourceGr
 		return err
 	}
 
+	// check to see if some user has dependency on the group
+	checker := privilege.GetPrivilegeManager(ctx)
+	if checker == nil {
+		return errors.New("miss privilege checker")
+	}
+	user, matched := checker.MatchUserResourceGroupName(groupName.L)
+	if matched {
+		err = errors.Errorf("user [%s] depends on the resource group to drop", user)
+		return err
+	}
+
 	job := &model.Job{
 		SchemaID:   group.ID,
 		SchemaName: group.Name.L,

ddl/resource_group_test.go

@@ -160,6 +160,10 @@ func TestResourceGroupBasic(t *testing.T) {
 	tk.MustGetErrCode("create user usr_fail resource group nil_group", mysql.ErrResourceGroupNotExists)
 	tk.MustExec("create user user2")
 	tk.MustGetErrCode("alter user user2 resource group nil_group", mysql.ErrResourceGroupNotExists)
+
+	tk.MustExec("create resource group do_not_delete_rg rru_per_sec=100 wru_per_sec=200")
+	tk.MustExec("create user usr3 resource group do_not_delete_rg")
+	tk.MustContainErrMsg("drop resource group do_not_delete_rg", "user [usr3] depends on the resource group to drop")
 }
 
 func testResourceGroupNameFromIS(t *testing.T, ctx sessionctx.Context, name string) *model.ResourceGroupInfo {

errno/errname.go

@@ -1103,7 +1103,7 @@ var MySQLErrName = map[uint16]*mysql.ErrMessage{
 	ErrResourceGroupNotExists:          mysql.Message("Unknown resource group '%-.192s'", nil),
 
 	ErrColumnInChange:               mysql.Message("column %s id %d does not exist, this column may have been updated by other DDL ran in parallel", nil),
-	ErrResourceGroupSupportDisabled: mysql.Message("Resource group feature is disabled", nil),
+	ErrResourceGroupSupportDisabled: mysql.Message("Resource control feature is disabled. Run `SET GLOBAL tidb_enable_resource_control='on'` to enable the feature", nil),
 
 	// TiKV/PD errors.
 	ErrPDServerTimeout:           mysql.Message("PD server timeout: %s", nil),

errors.toml

@@ -2538,7 +2538,7 @@ Unknown resource group '%-.192s'
 
 ["schema:8250"]
 error = '''
-Resource group feature is disabled
+Resource control feature is disabled. Run `SET GLOBAL tidb_enable_resource_control='on'` to enable the feature
 '''
 
 ["session:8002"]

privilege/privilege.go

@@ -87,6 +87,9 @@ type Manager interface {
 	// MatchIdentity matches an identity
 	MatchIdentity(user, host string, skipNameResolve bool) (string, string, bool)
 
+	// MatchUserResourceGroupName matches a user with specified resource group name
+	MatchUserResourceGroupName(resourceGroupName string) (string, bool)
+
 	// DBIsVisible returns true is the database is visible to current user.
 	DBIsVisible(activeRole []*auth.RoleIdentity, db string) bool
 

privilege/privileges/cache.go

@@ -1014,6 +1014,17 @@ func (p *MySQLPrivilege) matchIdentity(user, host string, skipNameResolve bool)
 	return nil
 }
 
+// matchResoureGroup finds an identity to match resource group.
+func (p *MySQLPrivilege) matchResoureGroup(resourceGroupName string) *UserRecord {
+	for i := 0; i < len(p.User); i++ {
+		record := &p.User[i]
+		if record.ResourceGroup == resourceGroupName {
+			return record
+		}
+	}
+	return nil
+}
+
 // connectionVerification verifies the username + hostname according to exact
 // match from the mysql.user privilege table. call matchIdentity() first if you
 // do not have an exact match yet.

privilege/privileges/privileges.go

@@ -310,6 +310,16 @@ func (p *UserPrivileges) MatchIdentity(user, host string, skipNameResolve bool)
 	return "", "", false
 }
 
+// MatchUserResourceGroupName implements the Manager interface.
+func (p *UserPrivileges) MatchUserResourceGroupName(resourceGroupName string) (u string, success bool) {
+	mysqlPriv := p.Handle.Get()
+	record := mysqlPriv.matchResoureGroup(resourceGroupName)
+	if record != nil {
+		return record.User, true
+	}
+	return "", false
+}
+
 // GetAuthWithoutVerification implements the Manager interface.
 func (p *UserPrivileges) GetAuthWithoutVerification(user, host string) (success bool) {
 	if SkipWithGrant {