114 lines
2.9 KiB
Go
114 lines
2.9 KiB
Go
// Copyright 2016 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package expression
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import (
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"strings"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/ast"
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)
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// Schema stands for the row schema get from input.
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type Schema struct {
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Columns []*Column
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}
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// String implements fmt.Stringer interface.
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func (s Schema) String() string {
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colStrs := make([]string, 0, len(s.Columns))
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for _, col := range s.Columns {
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colStrs = append(colStrs, col.String())
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}
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return "[" + strings.Join(colStrs, ",") + "]"
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}
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// Clone copies the total schema.
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func (s Schema) Clone() Schema {
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result := NewSchema(make([]*Column, 0, s.Len()))
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for _, col := range s.Columns {
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newCol := *col
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result.Append(&newCol)
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}
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return result
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}
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// FindColumn finds an Column from schema for a ast.ColumnName. It compares the db/table/column names.
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// If there are more than one result, it will raise ambiguous error.
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func (s Schema) FindColumn(astCol *ast.ColumnName) (*Column, error) {
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dbName, tblName, colName := astCol.Schema, astCol.Table, astCol.Name
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idx := -1
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for i, col := range s.Columns {
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if (dbName.L == "" || dbName.L == col.DBName.L) &&
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(tblName.L == "" || tblName.L == col.TblName.L) &&
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(colName.L == col.ColName.L) {
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if idx == -1 {
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idx = i
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} else {
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return nil, errors.Errorf("Column %s is ambiguous", col.String())
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}
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}
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}
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if idx == -1 {
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return nil, nil
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}
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return s.Columns[idx], nil
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}
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// InitColumnIndices sets indices for columns in schema.
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func (s Schema) InitColumnIndices() {
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for i, c := range s.Columns {
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c.Index = i
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}
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}
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// RetrieveColumn retrieves column in expression from the columns in schema.
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func (s Schema) RetrieveColumn(col *Column) *Column {
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index := s.GetColumnIndex(col)
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if index != -1 {
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return s.Columns[index]
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}
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return nil
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}
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// GetColumnIndex finds the index for a column.
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func (s Schema) GetColumnIndex(col *Column) int {
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for i, c := range s.Columns {
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if c.FromID == col.FromID && c.Position == col.Position {
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return i
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}
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}
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return -1
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}
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// Len returns the number of columns in schema.
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func (s Schema) Len() int {
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return len(s.Columns)
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}
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// Append append new column to the columns stored in schema.
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func (s *Schema) Append(col *Column) {
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s.Columns = append(s.Columns, col)
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}
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// MergeSchema will merge two schema into one schema.
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func MergeSchema(lSchema, rSchema Schema) Schema {
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return NewSchema(append(lSchema.Clone().Columns, rSchema.Clone().Columns...))
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}
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// NewSchema returns a schema made by its parameter.
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func NewSchema(cols []*Column) Schema {
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return Schema{Columns: cols}
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}
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