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*: add scope check when get system variables #6958

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merged 6 commits into from
Jul 3, 2018
Merged

*: add scope check when get system variables #6958

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8fb0a84
*: add scope check when get system variables
spongedu Jul 2, 2018
3781767
fix format
spongedu Jul 2, 2018
ded54b4
Merge branch 'master' into 0703
spongedu Jul 3, 2018
1e7805f
Refine errors
spongedu Jul 3, 2018
13f1cfd
Fix comment
spongedu Jul 3, 2018
a79d5ea
Merge remote-tracking branch 'upstream/master' into 0703
spongedu Jul 3, 2018
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2 changes: 2 additions & 0 deletions ast/expressions.go
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Expand Up @@ -944,6 +944,8 @@ type VariableExpr struct {
IsGlobal bool
// IsSystem indicates whether this variable is a system variable in current session.
IsSystem bool
// ExplicitScope indicates whether this variable scope is set explicitly.
ExplicitScope bool
// Value is the variable value.
Value ExprNode
}
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5 changes: 3 additions & 2 deletions parser/parser.y
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Expand Up @@ -5008,6 +5008,7 @@ SystemVariable:
{
v := strings.ToLower($1)
var isGlobal bool
explicitScope := true
if strings.HasPrefix(v, "@@global.") {
isGlobal = true
v = strings.TrimPrefix(v, "@@global.")
Expand All @@ -5016,9 +5017,9 @@ SystemVariable:
} else if strings.HasPrefix(v, "@@local.") {
v = strings.TrimPrefix(v, "@@local.")
} else if strings.HasPrefix(v, "@@") {
v = strings.TrimPrefix(v, "@@")
v, explicitScope = strings.TrimPrefix(v, "@@"), false
}
$$ = &ast.VariableExpr{Name: v, IsGlobal: isGlobal, IsSystem: true}
$$ = &ast.VariableExpr{Name: v, IsGlobal: isGlobal, IsSystem: true, ExplicitScope: explicitScope}
}

UserVariable:
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7 changes: 7 additions & 0 deletions plan/expression_rewriter.go
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Expand Up @@ -781,6 +781,13 @@ func (er *expressionRewriter) rewriteVariable(v *ast.VariableExpr) {
}
var val string
var err error
if v.ExplicitScope {
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Why should we care if it is set explicitly or not?

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if the scope constraint is not set explicitly, the behavior is to choose the right scope automatically. So the scope check should't happen here, logically. For example:
for a global variable max_connections, select @@max_connections works, and for a session variable warning_count, select @@warnging_count works as well.

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You are right. I got something here:

For a reference to a system variable in an expression as @@var_name (rather than with @@global. or @@session.), MySQL returns the session value if it exists and the global value otherwise. This differs from SET @@var_name = expr, which always refers to the session value.

err = variable.ValidateGetSystemVar(name, v.IsGlobal)
if err != nil {
er.err = errors.Trace(err)
return
}
}
if v.IsGlobal {
val, err = variable.GetGlobalSystemVar(sessionVars, name)
} else {
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27 changes: 27 additions & 0 deletions session/session_test.go
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Expand Up @@ -371,6 +371,33 @@ func (s *testSessionSuite) TestGlobalVarAccessor(c *C) {
tk.MustExec("set @@global.autocommit=1")
}

func (s *testSessionSuite) TestGetSysVariables(c *C) {
tk := testkit.NewTestKitWithInit(c, s.store)

// Test ScopeSession
tk.MustExec("select @@warning_count")
tk.MustExec("select @@session.warning_count")
tk.MustExec("select @@local.warning_count")
_, err := tk.Exec("select @@global.warning_count")
c.Assert(terror.ErrorEqual(err, variable.ErrIncorrectScope), IsTrue)

// Test ScopeGlobal
tk.MustExec("select @@max_connections")
tk.MustExec("select @@global.max_connections")
_, err = tk.Exec("select @@session.max_connections")
c.Assert(terror.ErrorEqual(err, variable.ErrIncorrectScope), IsTrue)
_, err = tk.Exec("select @@local.max_connections")
c.Assert(terror.ErrorEqual(err, variable.ErrIncorrectScope), IsTrue)

// Test ScopeNone
tk.MustExec("select @@performance_schema_max_mutex_classes")
tk.MustExec("select @@global.performance_schema_max_mutex_classes")
_, err = tk.Exec("select @@session.performance_schema_max_mutex_classes")
c.Assert(terror.ErrorEqual(err, variable.ErrIncorrectScope), IsTrue)
_, err = tk.Exec("select @@local.performance_schema_max_mutex_classes")
c.Assert(terror.ErrorEqual(err, variable.ErrIncorrectScope), IsTrue)
}

func (s *testSessionSuite) TestRetryResetStmtCtx(c *C) {
tk := testkit.NewTestKitWithInit(c, s.store)
tk.MustExec("create table retrytxn (a int unique, b int)")
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14 changes: 7 additions & 7 deletions sessionctx/variable/sysvar.go
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Expand Up @@ -59,18 +59,18 @@ func GetSysVar(name string) *SysVar {
// Variable error codes.
const (
CodeUnknownStatusVar terror.ErrCode = 1
CodeUnknownSystemVar terror.ErrCode = 1193
CodeIncorrectScope terror.ErrCode = 1238
CodeUnknownTimeZone terror.ErrCode = 1298
CodeReadOnly terror.ErrCode = 1621
CodeUnknownSystemVar terror.ErrCode = mysql.ErrUnknownSystemVariable
CodeIncorrectScope terror.ErrCode = mysql.ErrIncorrectGlobalLocalVar
CodeUnknownTimeZone terror.ErrCode = mysql.ErrUnknownTimeZone
CodeReadOnly terror.ErrCode = mysql.ErrVariableIsReadonly
)

// Variable errors
var (
UnknownStatusVar = terror.ClassVariable.New(CodeUnknownStatusVar, "unknown status variable")
UnknownSystemVar = terror.ClassVariable.New(CodeUnknownSystemVar, "unknown system variable '%s'")
ErrIncorrectScope = terror.ClassVariable.New(CodeIncorrectScope, "Incorrect variable scope")
ErrUnknownTimeZone = terror.ClassVariable.New(CodeUnknownTimeZone, "unknown or incorrect time zone: %s")
UnknownSystemVar = terror.ClassVariable.New(CodeUnknownSystemVar, mysql.MySQLErrName[mysql.ErrUnknownSystemVariable])
ErrIncorrectScope = terror.ClassVariable.New(CodeIncorrectScope, mysql.MySQLErrName[mysql.ErrIncorrectGlobalLocalVar])
ErrUnknownTimeZone = terror.ClassVariable.New(CodeUnknownTimeZone, mysql.MySQLErrName[mysql.ErrUnknownTimeZone])
ErrReadOnly = terror.ClassVariable.New(CodeReadOnly, "variable is read only")
)

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19 changes: 19 additions & 0 deletions sessionctx/variable/varsutil.go
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Expand Up @@ -137,6 +137,25 @@ func SetSessionSystemVar(vars *SessionVars, name string, value types.Datum) erro
return vars.SetSystemVar(name, sVal)
}

// ValidateGetSystemVar checks if system variable exists and validates its scope when get system variable.
func ValidateGetSystemVar(name string, isGlobal bool) error {
sysVar, exists := SysVars[name]
if !exists {
return UnknownSystemVar.GenByArgs(name)
}
switch sysVar.Scope {
case ScopeGlobal, ScopeNone:
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why handle ScopeGlobal and ScopeNone together?

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ScopeNone variables are global variables that can't be modified dynamically

if !isGlobal {
return ErrIncorrectScope.GenByArgs(name, "GLOBAL")
}
case ScopeSession:
if isGlobal {
return ErrIncorrectScope.GenByArgs(name, "SESSION")
}
}
return nil
}

// TiDBOptOn could be used for all tidb session variable options, we use "ON"/1 to turn on those options.
func TiDBOptOn(opt string) bool {
return strings.EqualFold(opt, "ON") || opt == "1"
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