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base.go
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base.go
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// Copyright (c) 2013 Couchbase, 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 xpipeline
import (
"fmt"
"runtime/debug"
"github.com/couchbaselabs/clog"
"github.com/couchbaselabs/dparval"
"github.com/couchbaselabs/tuqtng/ast"
"github.com/couchbaselabs/tuqtng/misc"
"github.com/couchbaselabs/tuqtng/network"
"github.com/couchbaselabs/tuqtng/query"
)
type BaseOperator struct {
Source Operator
itemChannel dparval.ValueChannel
supportChannel PipelineSupportChannel
upstreamStopChannel misc.StopChannel
downstreamStopChannel misc.StopChannel
query network.Query
}
func NewBaseOperator() *BaseOperator {
return &BaseOperator{
itemChannel: make(dparval.ValueChannel),
supportChannel: make(PipelineSupportChannel),
upstreamStopChannel: make(misc.StopChannel),
}
}
func (this *BaseOperator) SetSource(source Operator) {
this.Source = source
}
func (this *BaseOperator) GetChannels() (dparval.ValueChannel, PipelineSupportChannel) {
return this.itemChannel, this.supportChannel
}
func (this *BaseOperator) SendItem(item *dparval.Value) bool {
ok := true
for ok {
select {
case this.itemChannel <- item:
return true
case _, ok = <-this.downstreamStopChannel:
// someone closed the stop channel
}
}
return ok
}
func (this *BaseOperator) SendError(err query.Error) bool {
ok := true
for ok {
select {
case this.supportChannel <- err:
if err.IsFatal() {
return false
}
return true
case _, ok = <-this.downstreamStopChannel:
// someone closed the stop channel
}
}
return false
}
func (this *BaseOperator) SendOther(obj interface{}) bool {
ok := true
for ok {
select {
case this.supportChannel <- obj:
return true
case _, ok = <-this.downstreamStopChannel:
// someone closed the stop channel
}
}
return false
}
func (this *BaseOperator) RunOperator(oper Operator, stopChannel misc.StopChannel) {
defer close(this.itemChannel)
defer close(this.supportChannel)
defer close(this.upstreamStopChannel)
// this MUST be here so that it runs before the channels are closed
defer this.RecoverPanic()
this.downstreamStopChannel = stopChannel
go this.Source.Run(this.upstreamStopChannel)
var item *dparval.Value
var obj interface{}
sourceItemChannel, supportChannel := this.Source.GetChannels()
ok := true
for ok {
select {
case item, ok = <-sourceItemChannel:
if ok {
ok = oper.processItem(item)
}
case obj, ok = <-supportChannel:
if ok {
switch obj := obj.(type) {
case query.Error:
ok = this.SendError(obj)
default:
ok = this.SendOther(obj)
}
}
case _, ok = <-stopChannel:
// downstream has asked us to stop
}
}
oper.afterItems()
}
func (this *BaseOperator) RecoverPanic() {
r := recover()
if r != nil {
clog.Error(fmt.Errorf("Query Execution Panic: %v\n%s", r, debug.Stack()))
this.SendError(query.NewError(nil, "Panic In Exeuction Pipeline"))
}
}
func (this *BaseOperator) SetQuery(q network.Query) {
this.query = q
}
func (this *BaseOperator) Evaluate(e ast.Expression, item *dparval.Value) (*dparval.Value, error) {
// first ensure the query is avaliable
item.SetAttachment("query", this.query)
return e.Evaluate(item)
}
func (this *BaseOperator) projectedValueOfResultExpression(item *dparval.Value, resultExpr *ast.ResultExpression) (*dparval.Value, error) {
if resultExpr.Star {
if resultExpr.Expr != nil {
// evaluate this expression first
val, err := this.Evaluate(resultExpr.Expr, item)
if err != nil {
return nil, err
}
if val.Type() == dparval.OBJECT {
return val, nil
}
} else {
return item, nil
}
} else if resultExpr.Expr != nil {
// evaluate the expression
val, err := this.Evaluate(resultExpr.Expr, item)
if err != nil {
return nil, err
}
return val, err
}
return nil, nil
}