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finder_paged.go
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finder_paged.go
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package v2
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"github.com/grafana/tempo/pkg/model"
"github.com/grafana/tempo/tempodb/encoding/common"
)
type PagedFinder struct {
r common.DataReader
index common.IndexReader
combiner model.ObjectCombiner
objectRW common.ObjectReaderWriter
dataEncoding string
}
// NewPagedFinder returns a paged. This finder is used for searching
// a set of records and returning an object. If a set of consecutive records has
// matching ids they will be combined using the ObjectCombiner.
func NewPagedFinder(index common.IndexReader, r common.DataReader, combiner model.ObjectCombiner, objectRW common.ObjectReaderWriter, dataEncoding string) *PagedFinder {
return &PagedFinder{
r: r,
index: index,
combiner: combiner,
objectRW: objectRW,
dataEncoding: dataEncoding,
}
}
func (f *PagedFinder) Find(ctx context.Context, id common.ID) ([]byte, error) {
var bytesFound []byte
record, i, err := f.index.Find(ctx, id)
if err != nil {
return nil, err
}
if record == nil {
return nil, nil
}
for {
bytesOne, err := f.findOne(ctx, id, *record)
if err != nil {
return nil, err
}
if f.combiner == nil {
bytesFound = bytesOne
break
}
bytesFound, _, err = f.combiner.Combine(f.dataEncoding, bytesFound, bytesOne)
if err != nil {
return nil, fmt.Errorf("failed to combine in Find: %w", err)
}
// we need to check the next record to see if it also matches our id
i++
record, err = f.index.At(ctx, i)
if err != nil {
return nil, err
}
if record == nil {
break
}
if !bytes.Equal(record.ID, id) {
break
}
}
return bytesFound, nil
}
func (f *PagedFinder) findOne(ctx context.Context, id common.ID, record common.Record) ([]byte, error) {
pages, _, err := f.r.Read(ctx, []common.Record{record}, nil, nil)
if err != nil {
return nil, err
}
if len(pages) == 0 {
return nil, errors.New("unexpected 0 length pages in findOne")
}
// dataReader is expected to return pages in the v0 format. so this works
iter := NewIterator(bytes.NewReader(pages[0]), f.objectRW)
if f.combiner != nil {
iter, err = NewDedupingIterator(iter, f.combiner, f.dataEncoding)
}
if err != nil {
return nil, err
}
for {
foundID, b, err := iter.Next(ctx)
if err == io.EOF {
break
}
if err != nil {
return nil, err
}
if bytes.Equal(foundID, id) {
return b, nil
}
}
return nil, nil
}