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eval_control_funcs.go
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/
eval_control_funcs.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 xeval
import (
"github.com/juju/errors"
"github.com/pingcap/tidb/util/types"
"github.com/pingcap/tipb/go-tipb"
)
func (e *Evaluator) evalControlFuncs(expr *tipb.Expr) (d types.Datum, err error) {
switch expr.GetTp() {
case tipb.ExprType_Case:
return e.evalCaseWhen(expr)
case tipb.ExprType_If:
return e.evalIf(expr)
case tipb.ExprType_NullIf:
return e.evalNullIf(expr)
case tipb.ExprType_IfNull:
return e.evalIfNull(expr)
}
return
}
func (e *Evaluator) evalCaseWhen(expr *tipb.Expr) (d types.Datum, err error) {
l := len(expr.Children)
for i := 0; i < l-1; i += 2 {
child, err := e.Eval(expr.Children[i])
if err != nil {
return d, errors.Trace(err)
}
if child.IsNull() {
continue
}
x, err := child.ToBool(e.StatementCtx)
if err != nil {
return d, errors.Trace(err)
}
if x == 1 {
ans, err := e.Eval(expr.Children[i+1])
if err != nil {
return d, errors.Trace(err)
}
return ans, nil
}
}
if l%2 == 1 { // Else statement
ans, err := e.Eval(expr.Children[l-1])
if err != nil {
return d, errors.Trace(err)
}
return ans, nil
}
return d, nil
}
func (e *Evaluator) evalIf(expr *tipb.Expr) (d types.Datum, err error) {
if len(expr.Children) != 3 {
err = ErrInvalid.Gen("IF needs 3 operands but got %d", len(expr.Children))
return
}
condTrue := false
child1, err := e.Eval(expr.Children[0])
if err != nil {
return d, errors.Trace(err)
}
if !child1.IsNull() {
var x int64
x, err = child1.ToBool(e.StatementCtx)
if err != nil {
return d, errors.Trace(err)
}
if x == 1 {
condTrue = true
}
}
if condTrue {
d, err = e.Eval(expr.Children[1])
} else {
d, err = e.Eval(expr.Children[2])
}
return d, errors.Trace(err)
}
func (e *Evaluator) evalNullIf(expr *tipb.Expr) (d types.Datum, err error) {
left, right, err := e.evalTwoChildren(expr)
if err != nil {
return d, errors.Trace(err)
}
if left.IsNull() || right.IsNull() {
return left, nil
}
x, err := left.CompareDatum(e.StatementCtx, &right)
if err != nil {
return d, errors.Trace(err)
}
if x == 0 {
return d, nil
}
return left, nil
}
func (e *Evaluator) evalIfNull(expr *tipb.Expr) (d types.Datum, err error) {
left, right, err := e.evalTwoChildren(expr)
if err != nil {
return d, errors.Trace(err)
}
if left.IsNull() {
return right, nil
}
return left, nil
}