tidb generated_expr 源码
tidb generated_expr 代码
文件路径：/util/generatedexpr/generated_expr.go
// Copyright 2017 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package generatedexpr
import (
"fmt"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/parser"
"github.com/pingcap/tidb/parser/ast"
"github.com/pingcap/tidb/parser/charset"
"github.com/pingcap/tidb/parser/model"
"github.com/pingcap/tidb/util"
)
// nameResolver is the visitor to resolve table name and column name.
// it combines TableInfo and ColumnInfo to a generation expression.
type nameResolver struct {
tableInfo *model.TableInfo
err error
}
// Enter implements ast.Visitor interface.
func (*nameResolver) Enter(inNode ast.Node) (ast.Node, bool) {
return inNode, false
}
// Leave implements ast.Visitor interface.
func (nr *nameResolver) Leave(inNode ast.Node) (node ast.Node, ok bool) {
//nolint: revive,all_revive
switch v := inNode.(type) {
case *ast.ColumnNameExpr:
for _, col := range nr.tableInfo.Columns {
if col.Name.L == v.Name.Name.L {
v.Refer = &ast.ResultField{
Column: col,
Table: nr.tableInfo,
}
return inNode, true
}
}
nr.err = errors.Errorf("can't find column %s in %s", v.Name.Name.O, nr.tableInfo.Name.O)
return inNode, false
}
return inNode, true
}
// ParseExpression parses an ExprNode from a string.
// When TiDB loads infoschema from TiKV, `GeneratedExprString`
// of `ColumnInfo` is a string field, so we need to parse
// it into ast.ExprNode. This function is for that.
func ParseExpression(expr string) (node ast.ExprNode, err error) {
expr = fmt.Sprintf("select %s", expr)
charset, collation := charset.GetDefaultCharsetAndCollate()
stmts, _, err := parser.New().ParseSQL(expr,
parser.CharsetConnection(charset),
parser.CollationConnection(collation))
if err == nil {
node = stmts[0].(*ast.SelectStmt).Fields.Fields[0].Expr
}
return node, util.SyntaxError(err)
}
// SimpleResolveName resolves all column names in the expression node.
func SimpleResolveName(node ast.ExprNode, tblInfo *model.TableInfo) (ast.ExprNode, error) {
nr := nameResolver{tblInfo, nil}
if _, ok := node.Accept(&nr); !ok {
return nil, errors.Trace(nr.err)
}
return node, nil
}
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