ddl, kv: address comments.

ddl/alter.go

@@ -42,7 +42,7 @@ const (
 type ColumnPosition struct {
 	// ColumnPositionNone | ColumnPositionFirst | ColumnPositionAfter
 	Type int
-	// RelativeColumn is the column which is after the newly added column if type is ColumnPositionAfter.
+	// RelativeColumn is the column which is before the newly added column if type is ColumnPositionAfter.
 	RelativeColumn string
 }
 

ddl/ddl.go

@@ -202,7 +202,7 @@ func setColumnFlagWithConstraint(colMap map[string]*column.Col, v *coldef.TableC
 				continue
 			}
 			c.Flag |= mysql.PriKeyFlag
-			// primary key can not be NULL.
+			// Primary key can not be NULL.
 			c.Flag |= mysql.NotNullFlag
 		}
 	case coldef.ConstrUniq, coldef.ConstrUniqIndex, coldef.ConstrUniqKey:
@@ -457,7 +457,7 @@ func (d *ddl) addColumn(ctx context.Context, schema model.CIStr, tbl table.Table
 		// Insert position is after the mentioned column.
 		position = c.Offset + 1
 	}
-	// TODO: Set constraint
+	// TODO: set constraint
 	col, _, err := d.buildColumnAndConstraint(position, spec.Column)
 	if err != nil {
 		return errors.Trace(err)

kv/union_store.go

@@ -27,7 +27,7 @@ import (
 type conditionType int
 
 const (
-	// conditionIfNotExist means the condition is not exist.
+	// conditionIfNotExist means the condition doesn't exist.
 	conditionIfNotExist conditionType = iota + 1
 	// conditionIfEqual means the condition is equals.
 	conditionIfEqual