Tiny clean up util package.

util/arena/arena.go

@@ -13,21 +13,21 @@
 
 package arena
 
-// Allocator pre-allocates memory to
-// reduce memory allocation cost.
+// Allocator pre-allocates memory to reduce memory allocation cost.
 // It is not thread-safe.
 type Allocator interface {
-	// Alloc allocates memory with 0 len and n cap.
+	// Alloc allocates memory with 0 len and capacity cap.
 	Alloc(capacity int) []byte
 
 	// AllocWithLen allocates memory with length and capacity.
 	AllocWithLen(length int, capacity int) []byte
 
-	// Reset resets arena offset, make sure all the allocated memory are not used any more.
+	// Reset resets arena offset.
+	// Make sure all the allocated memory are not used any more.
 	Reset()
 }
 
-// SimpleAllocator is a simple implementation of ArenaAllocator
+// SimpleAllocator is a simple implementation of ArenaAllocator.
 type SimpleAllocator struct {
 	arena []byte
 	off   int
@@ -36,8 +36,8 @@ type SimpleAllocator struct {
 type stdAllocator struct {
 }
 
-func (a *stdAllocator) Alloc(n int) []byte {
-	return make([]byte, 0, n)
+func (a *stdAllocator) Alloc(capacity int) []byte {
+	return make([]byte, 0, capacity)
 }
 
 func (a *stdAllocator) AllocWithLen(length int, capacity int) []byte {
@@ -58,14 +58,14 @@ func NewAllocator(capacity int) *SimpleAllocator {
 }
 
 // Alloc implements Allocator.AllocBytes interface.
-func (s *SimpleAllocator) Alloc(capcity int) []byte {
-	if s.off+capcity < cap(s.arena) {
-		slice := s.arena[s.off:s.off : s.off+capcity]
-		s.off += capcity
+func (s *SimpleAllocator) Alloc(capacity int) []byte {
+	if s.off+capacity < cap(s.arena) {
+		slice := s.arena[s.off:s.off : s.off+capacity]
+		s.off += capacity
 		return slice
 	}
 
-	return make([]byte, 0, capcity)
+	return make([]byte, 0, capacity)
 }
 
 // AllocWithLen implements Allocator.AllocWithLen interface.

util/charset/charset.go

@@ -34,7 +34,7 @@ type Collation struct {
 
 var charsets = make(map[string]*Charset)
 
-// All the supported charsets should in the following table.
+// All the supported charsets should be in the following table.
 var charsetInfos = []*Charset{
 	{"utf8", nil, make(map[string]*Collation), "UTF-8 Unicode", 3},
 	{"latin1", nil, make(map[string]*Collation), "cp1252 West European", 1},

util/mock/context.go

@@ -23,7 +23,7 @@ import (
 
 var _ context.Context = (*Context)(nil)
 
-// Context is a mock context.Context for test.
+// Context represents mocked context.Context.
 type Context struct {
 	values map[fmt.Stringer]interface{}
 }
@@ -54,7 +54,7 @@ func (c *Context) FinishTxn(rollback bool) error {
 	return nil
 }
 
-// NewContext creates a mock context.Context.
+// NewContext creates a new mocked context.Context.
 func NewContext() context.Context {
 	return &Context{
 		values: make(map[fmt.Stringer]interface{}),

util/mock/mocks/plan.go

@@ -21,14 +21,14 @@ import (
 	"github.com/pingcap/tidb/util/format"
 )
 
-// Plan mocks a plan.Plan instance
+// Plan represents mocked plan.Plan.
 type Plan struct {
 	rset   *Recordset
 	rows   [][]interface{}
 	cursor int
 }
 
-// NewPlan creates a new MockPlan
+// NewPlan creates a new mocked plan.Plan.
 func NewPlan(rset *Recordset) *Plan {
 	return &Plan{rset: rset}
 }
@@ -60,7 +60,7 @@ func (p *Plan) Next(ctx context.Context) (row *plan.Row, err error) {
 	return
 }
 
-// Close implements plan.Plan Close interface{}
+// Close implements plan.Plan Close interface.
 func (p *Plan) Close() error {
 	p.cursor = 0
 	return nil

util/mock/mocks/recordset.go

@@ -19,15 +19,15 @@ import (
 	"github.com/pingcap/tidb/plan"
 )
 
-// Recordset represents mock Recordsets
+// Recordset represents mocked rset.Recordset.
 type Recordset struct {
 	rows   [][]interface{}
 	fields []string
 	offset int
 	cursor int
 }
 
-// NewRecordset creates a new mocked Recordset.
+// NewRecordset creates a new mocked rset.Recordset.
 func NewRecordset(rows [][]interface{}, fields []string, offset int) *Recordset {
 	return &Recordset{
 		rows:   rows,
@@ -58,12 +58,12 @@ func (r *Recordset) Fields() ([]*field.ResultField, error) {
 	return ret[:r.offset], nil
 }
 
-// FirstRow implements rset.Recordset.
+// FirstRow implements rset.Recordset FirstRow interface.
 func (r *Recordset) FirstRow() ([]interface{}, error) {
 	return r.rows[0], nil
 }
 
-// Rows implements rset.Recordset.
+// Rows implements rset.Recordset Rows interface.
 func (r *Recordset) Rows(limit, offset int) ([][]interface{}, error) {
 	var ret [][]interface{}
 	for _, row := range r.rows {
@@ -78,7 +78,7 @@ func (r *Recordset) SetFieldOffset(offset int) {
 	r.offset = offset
 }
 
-// Next implements rset.Recordset.
+// Next implements rset.Recordset Next interface.
 func (r *Recordset) Next() (row *plan.Row, err error) {
 	if r.cursor == len(r.rows) {
 		return
@@ -88,7 +88,7 @@ func (r *Recordset) Next() (row *plan.Row, err error) {
 	return
 }
 
-// Close implements rset.Recordset.
+// Close implements rset.Recordset Close interface.
 func (r *Recordset) Close() error {
 	r.cursor = 0
 	return nil

util/mock/mocks/statement.go

@@ -21,7 +21,7 @@ import (
 	"github.com/pingcap/tidb/util/format"
 )
 
-// Statement represents a mocked Statement.
+// Statement represents mocked stmt.Statement.
 type Statement struct {
 	text string
 	Rset *Recordset

util/prefix_helper.go

@@ -38,12 +38,13 @@ func hasPrefix(prefix []byte) kv.FnKeyCmp {
 func ScanMetaWithPrefix(txn kv.Transaction, prefix string, filter func([]byte, []byte) bool) error {
 	iter, err := txn.Seek([]byte(prefix), hasPrefix([]byte(prefix)))
 	if err != nil {
-		return err
+		return errors.Trace(err)
 	}
 	defer iter.Close()
+
 	for {
 		if err != nil {
-			return err
+			return errors.Trace(err)
 		}
 
 		if iter.Valid() && strings.HasPrefix(iter.Key(), prefix) {
@@ -61,21 +62,21 @@ func ScanMetaWithPrefix(txn kv.Transaction, prefix string, filter func([]byte, [
 
 // DelKeyWithPrefix deletes keys with prefix.
 func DelKeyWithPrefix(ctx context.Context, prefix string) error {
-	log.Debug("delKeyWithPrefix", prefix)
 	txn, err := ctx.GetTxn(false)
 	if err != nil {
-		return err
+		return errors.Trace(err)
 	}
 
 	var keys []string
 	iter, err := txn.Seek([]byte(prefix), hasPrefix([]byte(prefix)))
 	if err != nil {
-		return err
+		return errors.Trace(err)
 	}
+
 	defer iter.Close()
 	for {
 		if err != nil {
-			return err
+			return errors.Trace(err)
 		}
 
 		if iter.Valid() && strings.HasPrefix(iter.Key(), prefix) {
@@ -89,7 +90,7 @@ func DelKeyWithPrefix(ctx context.Context, prefix string) error {
 	for _, key := range keys {
 		err := txn.Delete([]byte(key))
 		if err != nil {
-			return err
+			return errors.Trace(err)
 		}
 	}
 

util/types/compare.go

@@ -55,7 +55,7 @@ func CompareFloat64(x, y float64) int {
 	return 1
 }
 
-// CompareInteger  returns an integer comparing the int64 x to the uint64 y.
+// CompareInteger returns an integer comparing the int64 x to the uint64 y.
 func CompareInteger(x int64, y uint64) int {
 	if x < 0 {
 		return -1
@@ -74,24 +74,24 @@ func CompareString(x, y string) int {
 	return 1
 }
 
-// compareFloatString compares float a to float-formated string s.
+// compareFloatString compares float a with string s.
 // compareFloatString first parses s to a float value, if failed, returns error.
 func compareFloatString(a float64, s string) (int, error) {
-	// MySQL will convert string to a float point value
-	// MySQL use a very loose conversation, e.g, 123.abc -> 123
-	// we should do a trade off whether supporting this feature or using a strict mode
-	// now we use a strict mode
+	// MySQL will convert string to a float point value.
+	// MySQL uses a very loose conversation, e.g, 123.abc -> 123
+	// We should do a trade off whether supporting this feature or using a strict mode.
+	// Now we use a strict mode.
 	b, err := StrToFloat(s)
 	if err != nil {
-		return 0, err
+		return 0, errors.Trace(err)
 	}
 	return CompareFloat64(a, b), nil
 }
 
-// compareStringFloat compares float-formated string s to float a.
+// compareStringFloat compares string s with float a.
 func compareStringFloat(s string, a float64) (int, error) {
 	n, err := compareFloatString(a, s)
-	return -n, err
+	return -n, errors.Trace(err)
 }
 
 func coerceCompare(a, b interface{}) (x interface{}, y interface{}, err error) {
@@ -117,7 +117,7 @@ func coerceCompare(a, b interface{}) (x interface{}, y interface{}, err error) {
 		err = errors.Errorf("invalid comapre type %T cmp %T", a, b)
 	}
 
-	return x, y, err
+	return x, y, errors.Trace(err)
 }
 
 func compareRow(a, b []interface{}) (int, error) {
@@ -136,7 +136,7 @@ func compareRow(a, b []interface{}) (int, error) {
 	return 0, nil
 }
 
-// Compare returns an integer comparing the interface a to b.
+// Compare returns an integer comparing the interface a with b.
 // a > b -> 1
 // a = b -> 0
 // a < b -> -1
@@ -166,7 +166,6 @@ func Compare(a, b interface{}) (int, error) {
 	}
 
 	// TODO: support compare time type with other int, float, decimal types.
-	// TODO: support hexadecimal type
 	switch x := a.(type) {
 	case float64:
 		switch y := b.(type) {
@@ -216,7 +215,7 @@ func Compare(a, b interface{}) (int, error) {
 		case string:
 			f, err := mysql.ConvertToDecimal(y)
 			if err != nil {
-				return 0, err
+				return 0, errors.Trace(err)
 			}
 			return x.Cmp(f), nil
 		}
@@ -233,15 +232,15 @@ func Compare(a, b interface{}) (int, error) {
 		case mysql.Decimal:
 			f, err := mysql.ConvertToDecimal(x)
 			if err != nil {
-				return 0, err
+				return 0, errors.Trace(err)
 			}
 			return f.Cmp(y), nil
 		case mysql.Time:
 			n, err := y.CompareString(x)
-			return -n, err
+			return -n, errors.Trace(err)
 		case mysql.Duration:
 			n, err := y.CompareString(x)
-			return -n, err
+			return -n, errors.Trace(err)
 		case mysql.Hex:
 			return CompareString(x, y.ToString()), nil
 		case mysql.Bit: