132 lines
3.1 KiB
Go
132 lines
3.1 KiB
Go
// Copyright 2013 The ql Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSES/QL-LICENSE file.
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// Copyright 2015 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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"fmt"
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"strings"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/context"
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)
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var (
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_ Expression = (*Call)(nil)
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)
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// Call is for function expression.
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type Call struct {
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// F is the function name.
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F string
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// Args is the function args.
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Args []Expression
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// Distinct only affetcts sum, avg, count, group_concat,
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// so we can ignore it in other functions
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Distinct bool
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}
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// NewCall creates a Call expression with function name f, function args arg and
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// a distinct flag whether this function supports distinct or not.
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func NewCall(f string, args []Expression, distinct bool) (v Expression, err error) {
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x := builtin[strings.ToLower(f)]
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if x.f == nil {
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return nil, errors.Errorf("undefined: %s", f)
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}
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if g, min, max := len(args), x.minArgs, x.maxArgs; g < min || (max != -1 && g > max) {
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a := []interface{}{}
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for _, v := range args {
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a = append(a, v)
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}
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return nil, badNArgs(min, f, a)
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}
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c := Call{F: f, Distinct: distinct}
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for _, Val := range args {
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if !Val.IsStatic() {
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c.Args = append(c.Args, Val)
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continue
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}
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eVal, err := Val.Eval(nil, nil)
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if err != nil {
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return nil, err
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}
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c.Args = append(c.Args, Value{eVal})
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}
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return &c, nil
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}
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// Clone implements the Expression Clone interface.
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func (c *Call) Clone() Expression {
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list := cloneExpressionList(c.Args)
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return &Call{F: c.F, Args: list, Distinct: c.Distinct}
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}
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// IsStatic implements the Expression IsStatic interface.
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func (c *Call) IsStatic() bool {
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v := builtin[strings.ToLower(c.F)]
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if v.f == nil || !v.isStatic {
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return false
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}
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for _, v := range c.Args {
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if !v.IsStatic() {
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return false
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}
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}
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return true
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}
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// String implements the Expression String interface.
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func (c *Call) String() string {
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distinct := ""
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if c.Distinct {
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distinct = "DISTINCT "
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}
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a := []string{}
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for _, v := range c.Args {
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a = append(a, v.String())
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}
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return fmt.Sprintf("%s(%s%s)", c.F, distinct, strings.Join(a, ", "))
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}
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// Eval implements the Expression Eval interface.
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func (c *Call) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
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f, ok := builtin[strings.ToLower(c.F)]
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if !ok {
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return nil, errors.Errorf("unknown function %s", c.F)
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}
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a := make([]interface{}, len(c.Args))
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for i, arg := range c.Args {
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if v, err = arg.Eval(ctx, args); err != nil {
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return nil, err
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}
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a[i] = v
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}
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if args != nil {
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args[ExprEvalFn] = c
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args[ExprEvalArgCtx] = ctx
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}
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return f.f(a, args)
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}
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