diff --git a/dialects/dameng.go b/dialects/dameng.go
index f4a075d5..5e92ec2f 100644
--- a/dialects/dameng.go
+++ b/dialects/dameng.go
@@ -622,9 +622,9 @@ func (db *dameng) SQLType(c *schemas.Column) string {
 	hasLen2 := (c.Length2 > 0)
 
 	if hasLen2 {
-		res += "(" + strconv.Itoa(c.Length) + "," + strconv.Itoa(c.Length2) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + "," + strconv.FormatInt(c.Length2, 10) + ")"
 	} else if hasLen1 {
-		res += "(" + strconv.Itoa(c.Length) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + ")"
 	}
 	return res
 }
@@ -729,11 +729,11 @@ func (db *dameng) CreateTableSQL(ctx context.Context, queryer core.Queryer, tabl
 func (db *dameng) SetQuotePolicy(quotePolicy QuotePolicy) {
 	switch quotePolicy {
 	case QuotePolicyNone:
-		var q = damengQuoter
+		q := damengQuoter
 		q.IsReserved = schemas.AlwaysNoReserve
 		db.quoter = q
 	case QuotePolicyReserved:
-		var q = damengQuoter
+		q := damengQuoter
 		q.IsReserved = db.IsReserved
 		db.quoter = q
 	case QuotePolicyAlways:
@@ -792,7 +792,7 @@ type dmClobObject interface {
 	ReadString(int, int) (string, error)
 }
 
-//var _ dmClobObject = &dm.DmClob{}
+// var _ dmClobObject = &dm.DmClob{}
 
 func (d *dmClobScanner) Scan(data interface{}) error {
 	if data == nil {
@@ -927,7 +927,7 @@ func (db *dameng) GetColumns(queryer core.Queryer, ctx context.Context, tableNam
 		var (
 			ignore     bool
 			dt         string
-			len1, len2 int
+			len1, len2 int64
 		)
 
 		dts := strings.Split(dataType.String, "(")
@@ -935,10 +935,10 @@ func (db *dameng) GetColumns(queryer core.Queryer, ctx context.Context, tableNam
 		if len(dts) > 1 {
 			lens := strings.Split(dts[1][:len(dts[1])-1], ",")
 			if len(lens) > 1 {
-				len1, _ = strconv.Atoi(lens[0])
-				len2, _ = strconv.Atoi(lens[1])
+				len1, _ = strconv.ParseInt(lens[0], 10, 64)
+				len2, _ = strconv.ParseInt(lens[1], 10, 64)
 			} else {
-				len1, _ = strconv.Atoi(lens[0])
+				len1, _ = strconv.ParseInt(lens[0], 10, 64)
 			}
 		}
 
@@ -972,9 +972,9 @@ func (db *dameng) GetColumns(queryer core.Queryer, ctx context.Context, tableNam
 		}
 
 		if col.SQLType.Name == "TIMESTAMP" {
-			col.Length = int(dataScale.Int64)
+			col.Length = dataScale.Int64
 		} else {
-			col.Length = int(dataLen.Int64)
+			col.Length = dataLen.Int64
 		}
 
 		if col.SQLType.IsTime() {
@@ -1140,8 +1140,8 @@ func (d *damengDriver) GenScanResult(colType string) (interface{}, error) {
 }
 
 func (d *damengDriver) Scan(ctx *ScanContext, rows *core.Rows, types []*sql.ColumnType, vv ...interface{}) error {
-	var scanResults = make([]interface{}, 0, len(types))
-	var replaces = make([]bool, 0, len(types))
+	scanResults := make([]interface{}, 0, len(types))
+	replaces := make([]bool, 0, len(types))
 	var err error
 	for i, v := range vv {
 		var replaced bool
diff --git a/dialects/mssql.go b/dialects/mssql.go
index 706a754a..1b6fe692 100644
--- a/dialects/mssql.go
+++ b/dialects/mssql.go
@@ -229,7 +229,7 @@ func (db *mssql) Init(uri *URI) error {
 func (db *mssql) SetParams(params map[string]string) {
 	defaultVarchar, ok := params["DEFAULT_VARCHAR"]
 	if ok {
-		var t = strings.ToUpper(defaultVarchar)
+		t := strings.ToUpper(defaultVarchar)
 		switch t {
 		case "NVARCHAR", "VARCHAR":
 			db.defaultVarchar = t
@@ -242,7 +242,7 @@ func (db *mssql) SetParams(params map[string]string) {
 
 	defaultChar, ok := params["DEFAULT_CHAR"]
 	if ok {
-		var t = strings.ToUpper(defaultChar)
+		t := strings.ToUpper(defaultChar)
 		switch t {
 		case "NCHAR", "CHAR":
 			db.defaultChar = t
@@ -375,9 +375,9 @@ func (db *mssql) SQLType(c *schemas.Column) string {
 	hasLen2 := (c.Length2 > 0)
 
 	if hasLen2 {
-		res += "(" + strconv.Itoa(c.Length) + "," + strconv.Itoa(c.Length2) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + "," + strconv.FormatInt(c.Length2, 10) + ")"
 	} else if hasLen1 {
-		res += "(" + strconv.Itoa(c.Length) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + ")"
 	}
 	return res
 }
@@ -403,11 +403,11 @@ func (db *mssql) IsReserved(name string) bool {
 func (db *mssql) SetQuotePolicy(quotePolicy QuotePolicy) {
 	switch quotePolicy {
 	case QuotePolicyNone:
-		var q = mssqlQuoter
+		q := mssqlQuoter
 		q.IsReserved = schemas.AlwaysNoReserve
 		db.quoter = q
 	case QuotePolicyReserved:
-		var q = mssqlQuoter
+		q := mssqlQuoter
 		q.IsReserved = db.IsReserved
 		db.quoter = q
 	case QuotePolicyAlways:
@@ -475,7 +475,7 @@ func (db *mssql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 	colSeq := make([]string, 0)
 	for rows.Next() {
 		var name, ctype, vdefault string
-		var maxLen, precision, scale int
+		var maxLen, precision, scale int64
 		var nullable, isPK, defaultIsNull, isIncrement bool
 		err = rows.Scan(&name, &ctype, &maxLen, &precision, &scale, &nullable, &defaultIsNull, &vdefault, &isPK, &isIncrement)
 		if err != nil {
diff --git a/dialects/mysql.go b/dialects/mysql.go
index 31e7b788..6ed4a1be 100644
--- a/dialects/mysql.go
+++ b/dialects/mysql.go
@@ -330,9 +330,9 @@ func (db *mysql) SQLType(c *schemas.Column) string {
 	}
 
 	if hasLen2 {
-		res += "(" + strconv.Itoa(c.Length) + "," + strconv.Itoa(c.Length2) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + "," + strconv.FormatInt(c.Length2, 10) + ")"
 	} else if hasLen1 {
-		res += "(" + strconv.Itoa(c.Length) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + ")"
 	}
 
 	if isUnsigned {
@@ -444,7 +444,7 @@ func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 		// Remove the /* mariadb-5.3 */ suffix from coltypes
 		colName = strings.TrimSuffix(colName, "/* mariadb-5.3 */")
 		colType = strings.ToUpper(colName)
-		var len1, len2 int
+		var len1, len2 int64
 		if len(cts) == 2 {
 			idx := strings.Index(cts[1], ")")
 			if colType == schemas.Enum && cts[1][0] == '\'' { // enum
@@ -465,12 +465,12 @@ func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 				}
 			} else {
 				lens := strings.Split(cts[1][0:idx], ",")
-				len1, err = strconv.Atoi(strings.TrimSpace(lens[0]))
+				len1, err = strconv.ParseInt(strings.TrimSpace(lens[0]), 10, 64)
 				if err != nil {
 					return nil, nil, err
 				}
 				if len(lens) == 2 {
-					len2, err = strconv.Atoi(lens[1])
+					len2, err = strconv.ParseInt(lens[1], 10, 64)
 					if err != nil {
 						return nil, nil, err
 					}
@@ -479,7 +479,7 @@ func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 		} else {
 			switch colType {
 			case "MEDIUMTEXT", "LONGTEXT", "TEXT":
-				len1, err = strconv.Atoi(*maxLength)
+				len1, err = strconv.ParseInt(*maxLength, 10, 64)
 				if err != nil {
 					return nil, nil, err
 				}
diff --git a/dialects/oracle.go b/dialects/oracle.go
index 04652bd6..8328ff15 100644
--- a/dialects/oracle.go
+++ b/dialects/oracle.go
@@ -570,9 +570,9 @@ func (db *oracle) SQLType(c *schemas.Column) string {
 	hasLen2 := (c.Length2 > 0)
 
 	if hasLen2 {
-		res += "(" + strconv.Itoa(c.Length) + "," + strconv.Itoa(c.Length2) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + "," + strconv.FormatInt(c.Length2, 10) + ")"
 	} else if hasLen1 {
-		res += "(" + strconv.Itoa(c.Length) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + ")"
 	}
 	return res
 }
@@ -606,7 +606,7 @@ func (db *oracle) DropTableSQL(tableName string) (string, bool) {
 }
 
 func (db *oracle) CreateTableSQL(ctx context.Context, queryer core.Queryer, table *schemas.Table, tableName string) (string, bool, error) {
-	var sql = "CREATE TABLE "
+	sql := "CREATE TABLE "
 	if tableName == "" {
 		tableName = table.Name
 	}
@@ -641,11 +641,11 @@ func (db *oracle) CreateTableSQL(ctx context.Context, queryer core.Queryer, tabl
 func (db *oracle) SetQuotePolicy(quotePolicy QuotePolicy) {
 	switch quotePolicy {
 	case QuotePolicyNone:
-		var q = oracleQuoter
+		q := oracleQuoter
 		q.IsReserved = schemas.AlwaysNoReserve
 		db.quoter = q
 	case QuotePolicyReserved:
-		var q = oracleQuoter
+		q := oracleQuoter
 		q.IsReserved = db.IsReserved
 		db.quoter = q
 	case QuotePolicyAlways:
@@ -690,7 +690,7 @@ func (db *oracle) GetColumns(queryer core.Queryer, ctx context.Context, tableNam
 		col.Indexes = make(map[string]int)
 
 		var colName, colDefault, nullable, dataType, dataPrecision, dataScale *string
-		var dataLen int
+		var dataLen int64
 
 		err = rows.Scan(&colName, &colDefault, &dataType, &dataLen, &dataPrecision,
 			&dataScale, &nullable)
@@ -713,16 +713,16 @@ func (db *oracle) GetColumns(queryer core.Queryer, ctx context.Context, tableNam
 		var ignore bool
 
 		var dt string
-		var len1, len2 int
+		var len1, len2 int64
 		dts := strings.Split(*dataType, "(")
 		dt = dts[0]
 		if len(dts) > 1 {
 			lens := strings.Split(dts[1][:len(dts[1])-1], ",")
 			if len(lens) > 1 {
-				len1, _ = strconv.Atoi(lens[0])
-				len2, _ = strconv.Atoi(lens[1])
+				len1, _ = strconv.ParseInt(lens[0], 10, 64)
+				len2, _ = strconv.ParseInt(lens[1], 10, 64)
 			} else {
-				len1, _ = strconv.Atoi(lens[0])
+				len1, _ = strconv.ParseInt(lens[0], 10, 64)
 			}
 		}
 
diff --git a/dialects/postgres.go b/dialects/postgres.go
index ba73aad7..3c7ecb35 100644
--- a/dialects/postgres.go
+++ b/dialects/postgres.go
@@ -934,9 +934,9 @@ func (db *postgres) SQLType(c *schemas.Column) string {
 	hasLen2 := (c.Length2 > 0)
 
 	if hasLen2 {
-		res += "(" + strconv.Itoa(c.Length) + "," + strconv.Itoa(c.Length2) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + "," + strconv.FormatInt(c.Length2, 10) + ")"
 	} else if hasLen1 {
-		res += "(" + strconv.Itoa(c.Length) + ")"
+		res += "(" + strconv.FormatInt(c.Length, 10) + ")"
 	}
 	return res
 }
@@ -1110,9 +1110,9 @@ WHERE n.nspname= s.table_schema AND c.relkind = 'r'::char AND c.relname = $1%s A
 			return nil, nil, err
 		}
 
-		var maxLen int
+		var maxLen int64
 		if maxLenStr != nil {
-			maxLen, err = strconv.Atoi(*maxLenStr)
+			maxLen, err = strconv.ParseInt(*maxLenStr, 10, 64)
 			if err != nil {
 				return nil, nil, err
 			}
@@ -1186,7 +1186,7 @@ WHERE n.nspname= s.table_schema AND c.relkind = 'r'::char AND c.relname = $1%s A
 			startIdx := strings.Index(strings.ToLower(dataType), "string(")
 			if startIdx != -1 && strings.HasSuffix(dataType, ")") {
 				length := dataType[startIdx+8 : len(dataType)-1]
-				l, _ := strconv.Atoi(length)
+				l, _ := strconv.ParseInt(length, 10, 64)
 				col.SQLType = schemas.SQLType{Name: "STRING", DefaultLength: l, DefaultLength2: 0}
 			} else {
 				col.SQLType = schemas.SQLType{Name: strings.ToUpper(dataType), DefaultLength: 0, DefaultLength2: 0}
diff --git a/dialects/time.go b/dialects/time.go
index f0bbb765..cdc896be 100644
--- a/dialects/time.go
+++ b/dialects/time.go
@@ -23,7 +23,7 @@ func FormatColumnTime(dialect Dialect, dbLocation *time.Location, col *schemas.C
 		}
 	}
 
-	var tmZone = dbLocation
+	tmZone := dbLocation
 	if col.TimeZone != nil {
 		tmZone = col.TimeZone
 	}
@@ -34,15 +34,17 @@ func FormatColumnTime(dialect Dialect, dbLocation *time.Location, col *schemas.C
 	case schemas.Date:
 		return t.Format("2006-01-02"), nil
 	case schemas.Time:
-		var layout = "15:04:05"
+		layout := "15:04:05"
 		if col.Length > 0 {
-			layout += "." + strings.Repeat("0", col.Length)
+			// we can use int(...) casting here as it's very unlikely to a huge sized field
+			layout += "." + strings.Repeat("0", int(col.Length))
 		}
 		return t.Format(layout), nil
 	case schemas.DateTime, schemas.TimeStamp:
-		var layout = "2006-01-02 15:04:05"
+		layout := "2006-01-02 15:04:05"
 		if col.Length > 0 {
-			layout += "." + strings.Repeat("0", col.Length)
+			// we can use int(...) casting here as it's very unlikely to a huge sized field
+			layout += "." + strings.Repeat("0", int(col.Length))
 		}
 		return t.Format(layout), nil
 	case schemas.Varchar:
diff --git a/integrations/engine_test.go b/integrations/engine_test.go
index 905c4f24..730a424e 100644
--- a/integrations/engine_test.go
+++ b/integrations/engine_test.go
@@ -290,13 +290,11 @@ func TestGetColumnsComment(t *testing.T) {
 }
 
 func TestGetColumnsLength(t *testing.T) {
-	var max_length int
+	var max_length int64
 	switch testEngine.Dialect().URI().DBType {
-	case
-		schemas.POSTGRES:
+	case schemas.POSTGRES:
 		max_length = 0
-	case
-		schemas.MYSQL:
+	case schemas.MYSQL:
 		max_length = 65535
 	default:
 		t.Skip()
diff --git a/schemas/column.go b/schemas/column.go
index 4bbb6c2d..001769cd 100644
--- a/schemas/column.go
+++ b/schemas/column.go
@@ -26,8 +26,8 @@ type Column struct {
 	FieldIndex      []int  // Available only when parsed from a struct
 	SQLType         SQLType
 	IsJSON          bool
-	Length          int
-	Length2         int
+	Length          int64
+	Length2         int64
 	Nullable        bool
 	Default         string
 	Indexes         map[string]int
@@ -48,7 +48,7 @@ type Column struct {
 }
 
 // NewColumn creates a new column
-func NewColumn(name, fieldName string, sqlType SQLType, len1, len2 int, nullable bool) *Column {
+func NewColumn(name, fieldName string, sqlType SQLType, len1, len2 int64, nullable bool) *Column {
 	return &Column{
 		Name:            name,
 		IsJSON:          sqlType.IsJson(),
@@ -82,7 +82,7 @@ func (col *Column) ValueOf(bean interface{}) (*reflect.Value, error) {
 
 // ValueOfV returns column's filed of struct's value accept reflevt value
 func (col *Column) ValueOfV(dataStruct *reflect.Value) (*reflect.Value, error) {
-	var v = *dataStruct
+	v := *dataStruct
 	for _, i := range col.FieldIndex {
 		if v.Kind() == reflect.Ptr {
 			if v.IsNil() {
diff --git a/schemas/type.go b/schemas/type.go
index 8702862a..b8b30851 100644
--- a/schemas/type.go
+++ b/schemas/type.go
@@ -28,8 +28,8 @@ const (
 // SQLType represents SQL types
 type SQLType struct {
 	Name           string
-	DefaultLength  int
-	DefaultLength2 int
+	DefaultLength  int64
+	DefaultLength2 int64
 }
 
 // enumerates all columns types
diff --git a/tags/tag.go b/tags/tag.go
index 4e1f1ce7..55f5f4cf 100644
--- a/tags/tag.go
+++ b/tags/tag.go
@@ -99,33 +99,31 @@ type Context struct {
 // Handler describes tag handler for XORM
 type Handler func(ctx *Context) error
 
-var (
-	// defaultTagHandlers enumerates all the default tag handler
-	defaultTagHandlers = map[string]Handler{
-		"-":        IgnoreHandler,
-		"<-":       OnlyFromDBTagHandler,
-		"->":       OnlyToDBTagHandler,
-		"PK":       PKTagHandler,
-		"NULL":     NULLTagHandler,
-		"NOT":      NotTagHandler,
-		"AUTOINCR": AutoIncrTagHandler,
-		"DEFAULT":  DefaultTagHandler,
-		"CREATED":  CreatedTagHandler,
-		"UPDATED":  UpdatedTagHandler,
-		"DELETED":  DeletedTagHandler,
-		"VERSION":  VersionTagHandler,
-		"UTC":      UTCTagHandler,
-		"LOCAL":    LocalTagHandler,
-		"NOTNULL":  NotNullTagHandler,
-		"INDEX":    IndexTagHandler,
-		"UNIQUE":   UniqueTagHandler,
-		"CACHE":    CacheTagHandler,
-		"NOCACHE":  NoCacheTagHandler,
-		"COMMENT":  CommentTagHandler,
-		"EXTENDS":  ExtendsTagHandler,
-		"UNSIGNED": UnsignedTagHandler,
-	}
-)
+// defaultTagHandlers enumerates all the default tag handler
+var defaultTagHandlers = map[string]Handler{
+	"-":        IgnoreHandler,
+	"<-":       OnlyFromDBTagHandler,
+	"->":       OnlyToDBTagHandler,
+	"PK":       PKTagHandler,
+	"NULL":     NULLTagHandler,
+	"NOT":      NotTagHandler,
+	"AUTOINCR": AutoIncrTagHandler,
+	"DEFAULT":  DefaultTagHandler,
+	"CREATED":  CreatedTagHandler,
+	"UPDATED":  UpdatedTagHandler,
+	"DELETED":  DeletedTagHandler,
+	"VERSION":  VersionTagHandler,
+	"UTC":      UTCTagHandler,
+	"LOCAL":    LocalTagHandler,
+	"NOTNULL":  NotNullTagHandler,
+	"INDEX":    IndexTagHandler,
+	"UNIQUE":   UniqueTagHandler,
+	"CACHE":    CacheTagHandler,
+	"NOCACHE":  NoCacheTagHandler,
+	"COMMENT":  CommentTagHandler,
+	"EXTENDS":  ExtendsTagHandler,
+	"UNSIGNED": UnsignedTagHandler,
+}
 
 func init() {
 	for k := range schemas.SqlTypes {
@@ -312,16 +310,16 @@ func SQLTypeTagHandler(ctx *Context) error {
 	default:
 		var err error
 		if len(ctx.params) == 2 {
-			ctx.col.Length, err = strconv.Atoi(ctx.params[0])
+			ctx.col.Length, err = strconv.ParseInt(ctx.params[0], 10, 64)
 			if err != nil {
 				return err
 			}
-			ctx.col.Length2, err = strconv.Atoi(ctx.params[1])
+			ctx.col.Length2, err = strconv.ParseInt(ctx.params[1], 10, 64)
 			if err != nil {
 				return err
 			}
 		} else if len(ctx.params) == 1 {
-			ctx.col.Length, err = strconv.Atoi(ctx.params[0])
+			ctx.col.Length, err = strconv.ParseInt(ctx.params[0], 10, 64)
 			if err != nil {
 				return err
 			}
@@ -332,8 +330,8 @@ func SQLTypeTagHandler(ctx *Context) error {
 
 // ExtendsTagHandler describes extends tag handler
 func ExtendsTagHandler(ctx *Context) error {
-	var fieldValue = ctx.fieldValue
-	var isPtr = false
+	fieldValue := ctx.fieldValue
+	isPtr := false
 	switch fieldValue.Kind() {
 	case reflect.Ptr:
 		f := fieldValue.Type().Elem()
@@ -355,7 +353,7 @@ func ExtendsTagHandler(ctx *Context) error {
 			col.FieldName = fmt.Sprintf("%v.%v", ctx.col.FieldName, col.FieldName)
 			col.FieldIndex = append(ctx.col.FieldIndex, col.FieldIndex...)
 
-			var tagPrefix = ctx.col.FieldName
+			tagPrefix := ctx.col.FieldName
 			if len(ctx.params) > 0 {
 				col.Nullable = isPtr
 				tagPrefix = strings.Trim(ctx.params[0], "'")
@@ -378,7 +376,7 @@ func ExtendsTagHandler(ctx *Context) error {
 			}
 		}
 	default:
-		//TODO: warning
+		// TODO: warning
 	}
 	return ErrIgnoreField
 }