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evaluator.go
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/
evaluator.go
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// Copyright 2016 The Cockroach Authors.
//
// 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.
//
// Author: Irfan Sharif (irfansharif@cockroachlabs.com)
package distsqlrun
import (
"sync"
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/tracing"
"golang.org/x/net/context"
)
type evaluator struct {
flowCtx *FlowCtx
input RowSource
output RowReceiver
ctx context.Context
specExprs []Expression
exprs []exprHelper
exprTypes []sqlbase.ColumnType
rowAlloc sqlbase.EncDatumRowAlloc
}
var _ processor = &evaluator{}
func newEvaluator(
flowCtx *FlowCtx, spec *EvaluatorSpec, input RowSource, output RowReceiver,
) (*evaluator, error) {
ev := &evaluator{
flowCtx: flowCtx,
input: input,
output: output,
specExprs: spec.Exprs,
ctx: log.WithLogTag(flowCtx.Context, "eval", nil),
exprs: make([]exprHelper, len(spec.Exprs)),
exprTypes: make([]sqlbase.ColumnType, len(spec.Exprs)),
}
// Initialize the render expressions.
types := input.Types()
for i, expr := range ev.specExprs {
if err := ev.exprs[i].init(expr, types, ev.flowCtx.evalCtx); err != nil {
return nil, err
}
ev.exprTypes[i] = sqlbase.DatumTypeToColumnType(ev.exprs[i].expr.ResolvedType())
}
return ev, nil
}
// Run is part of the processor interface.
func (ev *evaluator) Run(wg *sync.WaitGroup) {
if wg != nil {
defer wg.Done()
}
ctx, span := tracing.ChildSpan(ev.ctx, "evaluator")
defer tracing.FinishSpan(span)
if log.V(2) {
log.Infof(ctx, "starting evaluator process")
defer log.Infof(ctx, "exiting evaluator")
}
for {
row, err := ev.input.NextRow()
if err != nil || row == nil {
ev.output.Close(err)
return
}
outRow, err := ev.eval(row)
if err != nil {
ev.output.Close(err)
return
}
if log.V(3) {
log.Infof(ctx, "pushing %s\n", outRow)
}
// Push the row to the output RowReceiver; stop if they don't need more
// rows.
if !ev.output.PushRow(outRow) {
if log.V(2) {
log.Infof(ctx, "no more rows required")
}
ev.output.Close(nil)
return
}
}
}
func (ev *evaluator) eval(row sqlbase.EncDatumRow) (sqlbase.EncDatumRow, error) {
outRow := ev.rowAlloc.AllocRow(len(ev.exprs))
for i := range ev.exprs {
datum, err := ev.exprs[i].eval(row)
if err != nil {
return nil, err
}
outRow[i] = sqlbase.DatumToEncDatum(ev.exprTypes[i], datum)
}
return outRow, nil
}