Function ParseExpression

pkg/util/generatedexpr/generated_expr.go:60–70

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.

(expr string)

// 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) {