/
schema.go
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/
schema.go
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// Copyright 2016 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package expression
import (
"strings"
"github.com/ducminhnguyen/gleam/sql/ast"
"github.com/juju/errors"
)
// KeyInfo stores the columns of one unique key or primary key.
type KeyInfo []*Column
// Clone copies the entire UniqueKey.
func (ki KeyInfo) Clone() KeyInfo {
result := make([]*Column, 0, len(ki))
for _, col := range ki {
newCol := *col
result = append(result, &newCol)
}
return result
}
// Schema stands for the row schema and unique key information get from input.
type Schema struct {
Columns []*Column
Keys []KeyInfo
}
// String implements fmt.Stringer interface.
func (s Schema) String() string {
colStrs := make([]string, 0, len(s.Columns))
for _, col := range s.Columns {
colStrs = append(colStrs, col.String())
}
ukStrs := make([]string, 0, len(s.Keys))
for _, key := range s.Keys {
ukColStrs := make([]string, 0, len(key))
for _, col := range key {
ukColStrs = append(ukColStrs, col.String())
}
ukStrs = append(ukStrs, "["+strings.Join(ukColStrs, ",")+"]")
}
return "Column: [" + strings.Join(colStrs, ",") + "] Unique key: [" + strings.Join(ukStrs, ",") + "]"
}
// Clone copies the total schema.
func (s Schema) Clone() Schema {
result := NewSchema(make([]*Column, 0, s.Len()))
keys := make([]KeyInfo, 0, len(s.Keys))
for _, col := range s.Columns {
newCol := *col
result.Append(&newCol)
}
for _, key := range s.Keys {
keys = append(keys, key.Clone())
}
result.SetUniqueKeys(keys)
return result
}
// FindColumn finds an Column from schema for a ast.ColumnName. It compares the db/table/column names.
// If there are more than one result, it will raise ambiguous error.
func (s Schema) FindColumn(astCol *ast.ColumnName) (*Column, error) {
dbName, tblName, colName := astCol.Schema, astCol.Table, astCol.Name
idx := -1
for i, col := range s.Columns {
if (dbName.L == "" || dbName.L == col.DBName.L) &&
(tblName.L == "" || tblName.L == col.TblName.L) &&
(colName.L == col.ColName.L) {
if idx == -1 {
idx = i
} else {
return nil, errors.Errorf("Column %s is ambiguous", col.String())
}
}
}
if idx == -1 {
return nil, nil
}
return s.Columns[idx], nil
}
// RetrieveColumn retrieves column in expression from the columns in schema.
func (s Schema) RetrieveColumn(col *Column) *Column {
index := s.GetColumnIndex(col)
if index != -1 {
return s.Columns[index]
}
return nil
}
// GetColumnIndex finds the index for a column.
func (s Schema) GetColumnIndex(col *Column) int {
for i, c := range s.Columns {
if c.FromID == col.FromID && c.Position == col.Position {
return i
}
}
return -1
}
// Len returns the number of columns in schema.
func (s Schema) Len() int {
return len(s.Columns)
}
// Append append new column to the columns stored in schema.
func (s *Schema) Append(col *Column) {
s.Columns = append(s.Columns, col)
}
// SetUniqueKeys will set the value of Schema.Keys.
func (s *Schema) SetUniqueKeys(keys []KeyInfo) {
s.Keys = keys
}
// GetColumnsIndices will return a slice which contains the position of each column in schema.
// If there is one column that doesn't match, nil will be returned.
func (s Schema) GetColumnsIndices(cols []*Column) (ret []int) {
ret = make([]int, 0, len(cols))
for _, col := range cols {
pos := s.GetColumnIndex(col)
if pos != -1 {
ret = append(ret, pos)
} else {
return nil
}
}
return
}
// MergeSchema will merge two schema into one schema.
func MergeSchema(lSchema, rSchema Schema) Schema {
tmpL := lSchema.Clone()
tmpR := rSchema.Clone()
ret := NewSchema(append(tmpL.Columns, tmpR.Columns...))
ret.SetUniqueKeys(append(tmpL.Keys, tmpR.Keys...))
return ret
}
// NewSchema returns a schema made by its parameter.
func NewSchema(cols []*Column) Schema {
return Schema{Columns: cols}
}