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readerbase.go
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readerbase.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: Radu Berinde (radu@cockroachlabs.com)
package distsqlrun
import (
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
"github.com/pkg/errors"
)
// readerBase implements basic code shared by tableReader and joinReader.
type readerBase struct {
flowCtx *FlowCtx
desc sqlbase.TableDescriptor
index *sqlbase.IndexDescriptor
isSecondaryIndex bool
fetcher sqlbase.RowFetcher
filter exprHelper
// colIdxMap maps ColumnIDs to indices into desc.Columns
colIdxMap map[sqlbase.ColumnID]int
outputCols []int
// Last row returned by the rowFetcher; it has one entry per table column.
row sqlbase.EncDatumRow
rowAlloc sqlbase.EncDatumRowAlloc
}
func (rb *readerBase) init(
flowCtx *FlowCtx,
desc *sqlbase.TableDescriptor,
indexIdx int,
filter Expression,
outputCols []uint32,
reverseScan bool,
) error {
rb.flowCtx = flowCtx
rb.desc = *desc
rb.outputCols = make([]int, len(outputCols))
for i, v := range outputCols {
rb.outputCols[i] = int(v)
}
numCols := len(rb.desc.Columns)
// Figure out which columns we need: the output columns plus any other
// columns used by the filter expression.
valNeededForCol := make([]bool, numCols)
for _, c := range rb.outputCols {
if c < 0 || c >= numCols {
return errors.Errorf("invalid column index %d", c)
}
valNeededForCol[c] = true
}
if filter.Expr != "" {
types := make([]sqlbase.ColumnType, numCols)
for i := range types {
types[i] = rb.desc.Columns[i].Type
}
if err := rb.filter.init(filter, types, flowCtx.evalCtx); err != nil {
return err
}
for c := 0; c < numCols; c++ {
valNeededForCol[c] = valNeededForCol[c] || rb.filter.vars.IndexedVarUsed(c)
}
}
// indexIdx is 0 for the primary index, or 1 to <num-indexes> for a
// secondary index.
if indexIdx < 0 || indexIdx > len(rb.desc.Indexes) {
return errors.Errorf("invalid indexIdx %d", indexIdx)
}
if indexIdx > 0 {
rb.index = &rb.desc.Indexes[indexIdx-1]
rb.isSecondaryIndex = true
} else {
rb.index = &rb.desc.PrimaryIndex
}
rb.colIdxMap = make(map[sqlbase.ColumnID]int, len(rb.desc.Columns))
for i, c := range rb.desc.Columns {
rb.colIdxMap[c.ID] = i
}
err := rb.fetcher.Init(&rb.desc, rb.colIdxMap, rb.index, reverseScan, rb.isSecondaryIndex,
rb.desc.Columns, valNeededForCol)
if err != nil {
return err
}
rb.row = make(sqlbase.EncDatumRow, len(rb.desc.Columns))
return nil
}
// nextRow processes table rows until it finds a row that passes the filter.
// Returns a nil row when there are no more rows.
func (rb *readerBase) nextRow() (sqlbase.EncDatumRow, error) {
for {
fetcherRow, err := rb.fetcher.NextRow()
if err != nil || fetcherRow == nil {
return nil, err
}
for i := range fetcherRow {
if !fetcherRow[i].IsUnset() {
rb.row[i] = fetcherRow[i]
}
}
passesFilter, err := rb.filter.evalFilter(rb.row)
if err != nil {
return nil, err
}
if passesFilter {
break
}
}
outRow := rb.rowAlloc.AllocRow(len(rb.outputCols))
for i, col := range rb.outputCols {
outRow[i] = rb.row[col]
}
return outRow, nil
}