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iterator.go
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iterator.go
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// Copyright (C) 2020 Storj Labs, Inc.
// See LICENSE for copying information.
package metabase
import (
"bytes"
"context"
"strings"
"github.com/zeebo/errs"
"storj.io/common/uuid"
"storj.io/private/tagsql"
)
// objectIterator enables iteration on objects in a bucket.
type objectsIterator struct {
db *DB
projectID uuid.UUID
bucketName []byte
status ObjectStatus
prefix ObjectKey
prefixLimit ObjectKey
batchSize int
recursive bool
includeCustomMetadata bool
includeSystemMetadata bool
curIndex int
curRows tagsql.Rows
cursor iterateCursor // not relative to prefix
skipPrefix ObjectKey // relative to prefix
doNextQuery func(context.Context, *objectsIterator) (_ tagsql.Rows, err error)
// failErr is set when either scan or next query fails during iteration.
failErr error
}
type iterateCursor struct {
Key ObjectKey
Version Version
StreamID uuid.UUID
Inclusive bool
}
func iterateAllVersionsWithStatus(ctx context.Context, db *DB, opts IterateObjectsWithStatus, fn func(context.Context, ObjectsIterator) error) (err error) {
defer mon.Task()(&ctx)(&err)
it := &objectsIterator{
db: db,
projectID: opts.ProjectID,
bucketName: []byte(opts.BucketName),
status: opts.Status,
prefix: opts.Prefix,
prefixLimit: prefixLimit(opts.Prefix),
batchSize: opts.BatchSize,
recursive: opts.Recursive,
includeCustomMetadata: opts.IncludeCustomMetadata,
includeSystemMetadata: opts.IncludeSystemMetadata,
curIndex: 0,
cursor: firstIterateCursor(opts.Recursive, opts.Cursor, opts.Prefix),
doNextQuery: doNextQueryAllVersionsWithStatus,
}
// start from either the cursor or prefix, depending on which is larger
if lessKey(it.cursor.Key, opts.Prefix) {
it.cursor.Key = opts.Prefix
it.cursor.Version = -1
it.cursor.Inclusive = true
}
return iterate(ctx, it, fn)
}
func iteratePendingObjectsByKey(ctx context.Context, db *DB, opts IteratePendingObjectsByKey, fn func(context.Context, ObjectsIterator) error) (err error) {
defer mon.Task()(&ctx)(&err)
cursor := opts.Cursor
if cursor.StreamID.IsZero() {
cursor.StreamID = uuid.UUID{}
}
it := &objectsIterator{
db: db,
projectID: opts.ProjectID,
bucketName: []byte(opts.BucketName),
prefix: "",
prefixLimit: "",
batchSize: opts.BatchSize,
recursive: true,
includeCustomMetadata: true,
includeSystemMetadata: true,
status: Pending,
curIndex: 0,
cursor: iterateCursor{
Key: opts.ObjectKey,
Version: 0,
StreamID: opts.Cursor.StreamID,
},
doNextQuery: doNextQueryStreamsByKey,
}
return iterate(ctx, it, fn)
}
func iterate(ctx context.Context, it *objectsIterator, fn func(context.Context, ObjectsIterator) error) (err error) {
batchsizeLimit.Ensure(&it.batchSize)
it.curRows, err = it.doNextQuery(ctx, it)
if err != nil {
return err
}
it.cursor.Inclusive = false
defer func() {
if rowsErr := it.curRows.Err(); rowsErr != nil {
err = errs.Combine(err, rowsErr)
}
err = errs.Combine(err, it.failErr, it.curRows.Close())
}()
return fn(ctx, it)
}
// Next returns true if there was another item and copy it in item.
func (it *objectsIterator) Next(ctx context.Context, item *ObjectEntry) bool {
if it.recursive {
return it.next(ctx, item)
}
// TODO: implement this on the database side
// skip until we are past the prefix we returned before.
if it.skipPrefix != "" {
for strings.HasPrefix(string(item.ObjectKey), string(it.skipPrefix)) {
if !it.next(ctx, item) {
return false
}
}
it.skipPrefix = ""
} else {
ok := it.next(ctx, item)
if !ok {
return false
}
}
// should this be treated as a prefix?
p := strings.IndexByte(string(item.ObjectKey), Delimiter)
if p >= 0 {
it.skipPrefix = item.ObjectKey[:p+1]
*item = ObjectEntry{
IsPrefix: true,
ObjectKey: item.ObjectKey[:p+1],
Status: it.status,
}
}
return true
}
// next returns true if there was another item and copy it in item.
func (it *objectsIterator) next(ctx context.Context, item *ObjectEntry) bool {
next := it.curRows.Next()
if !next {
if it.curIndex < it.batchSize {
return false
}
if it.curRows.Err() != nil {
return false
}
if !it.recursive {
afterPrefix := it.cursor.Key[len(it.prefix):]
p := bytes.IndexByte([]byte(afterPrefix), Delimiter)
if p >= 0 {
it.cursor.Key = it.prefix + prefixLimit(afterPrefix[:p+1])
it.cursor.StreamID = uuid.UUID{}
it.cursor.Version = 0
}
}
rows, err := it.doNextQuery(ctx, it)
if err != nil {
it.failErr = errs.Combine(it.failErr, err)
return false
}
if closeErr := it.curRows.Close(); closeErr != nil {
it.failErr = errs.Combine(it.failErr, closeErr, rows.Close())
return false
}
it.curRows = rows
it.curIndex = 0
if !it.curRows.Next() {
return false
}
}
err := it.scanItem(item)
if err != nil {
it.failErr = errs.Combine(it.failErr, err)
return false
}
it.curIndex++
it.cursor.Key = it.prefix + item.ObjectKey
it.cursor.Version = item.Version
it.cursor.StreamID = item.StreamID
return true
}
func doNextQueryAllVersionsWithStatus(ctx context.Context, it *objectsIterator) (_ tagsql.Rows, err error) {
defer mon.Task()(&ctx)(&err)
cursorCompare := ">"
if it.cursor.Inclusive {
cursorCompare = ">="
}
if it.prefixLimit == "" {
querySelectFields := querySelectorFields("object_key", it)
return it.db.db.QueryContext(ctx, `
SELECT
`+querySelectFields+`
FROM objects
WHERE
(project_id, bucket_name, object_key, version) `+cursorCompare+` ($1, $2, $4, $5)
AND (project_id, bucket_name) < ($1, $7)
AND status = $3
AND (expires_at IS NULL OR expires_at > now())
ORDER BY (project_id, bucket_name, object_key, version) ASC
LIMIT $6
`, it.projectID, it.bucketName,
it.status,
[]byte(it.cursor.Key), int(it.cursor.Version),
it.batchSize,
nextBucket(it.bucketName),
)
}
fromSubstring := 1
if it.prefix != "" {
fromSubstring = len(it.prefix) + 1
}
querySelectFields := querySelectorFields("SUBSTRING(object_key FROM $8)", it)
return it.db.db.QueryContext(ctx, `
SELECT
`+querySelectFields+`
FROM objects
WHERE
(project_id, bucket_name, object_key, version) `+cursorCompare+` ($1, $2, $4, $5)
AND (project_id, bucket_name, object_key) < ($1, $2, $6)
AND status = $3
AND (expires_at IS NULL OR expires_at > now())
ORDER BY (project_id, bucket_name, object_key, version) ASC
LIMIT $7
`, it.projectID, it.bucketName,
it.status,
[]byte(it.cursor.Key), int(it.cursor.Version),
[]byte(it.prefixLimit),
it.batchSize,
fromSubstring,
)
}
func querySelectorFields(objectKeyColumn string, it *objectsIterator) string {
querySelectFields := objectKeyColumn + `
,stream_id
,version
,encryption`
if it.includeSystemMetadata {
querySelectFields += `
,created_at
,expires_at
,segment_count
,total_plain_size
,total_encrypted_size
,fixed_segment_size`
}
if it.includeCustomMetadata {
querySelectFields += `
,encrypted_metadata_nonce
,encrypted_metadata
,encrypted_metadata_encrypted_key`
}
return querySelectFields
}
// nextBucket returns the lexicographically next bucket.
func nextBucket(b []byte) []byte {
xs := make([]byte, len(b)+1)
copy(xs, b)
return xs
}
// doNextQuery executes query to fetch the next batch returning the rows.
func doNextQueryStreamsByKey(ctx context.Context, it *objectsIterator) (_ tagsql.Rows, err error) {
defer mon.Task()(&ctx)(&err)
return it.db.db.QueryContext(ctx, `
SELECT
object_key, stream_id, version, encryption,
created_at, expires_at,
segment_count,
total_plain_size, total_encrypted_size, fixed_segment_size,
encrypted_metadata_nonce, encrypted_metadata, encrypted_metadata_encrypted_key
FROM objects
WHERE
project_id = $1 AND bucket_name = $2
AND object_key = $3
AND stream_id > $4::BYTEA
AND status = `+pendingStatus+`
ORDER BY stream_id ASC
LIMIT $5
`, it.projectID, it.bucketName,
[]byte(it.cursor.Key),
it.cursor.StreamID,
it.batchSize,
)
}
// scanItem scans doNextQuery results into ObjectEntry.
func (it *objectsIterator) scanItem(item *ObjectEntry) (err error) {
item.IsPrefix = false
item.Status = it.status
fields := []interface{}{
&item.ObjectKey,
&item.StreamID,
&item.Version,
encryptionParameters{&item.Encryption},
}
if it.includeSystemMetadata {
fields = append(fields,
&item.CreatedAt,
&item.ExpiresAt,
&item.SegmentCount,
&item.TotalPlainSize,
&item.TotalEncryptedSize,
&item.FixedSegmentSize,
)
}
if it.includeCustomMetadata {
fields = append(fields,
&item.EncryptedMetadataNonce,
&item.EncryptedMetadata,
&item.EncryptedMetadataEncryptedKey,
)
}
err = it.curRows.Scan(fields...)
if err != nil {
return err
}
return nil
}
func prefixLimit(a ObjectKey) ObjectKey {
if a == "" {
return ""
}
if a[len(a)-1] == 0xFF {
return a + "\x00"
}
key := []byte(a)
key[len(key)-1]++
return ObjectKey(key)
}
// lessKey returns whether a < b.
func lessKey(a, b ObjectKey) bool {
return bytes.Compare([]byte(a), []byte(b)) < 0
}
// firstIterateCursor adjust the cursor for a non-recursive iteration.
// The cursor is non-inclusive and we need to adjust to handle prefix as cursor properly.
// We return the next possible key from the prefix.
func firstIterateCursor(recursive bool, cursor IterateCursor, prefix ObjectKey) iterateCursor {
if recursive {
return iterateCursor{
Key: cursor.Key,
Version: cursor.Version,
}
}
// when the cursor does not match the prefix, we'll return the original cursor.
if !strings.HasPrefix(string(cursor.Key), string(prefix)) {
return iterateCursor{
Key: cursor.Key,
Version: cursor.Version,
}
}
// handle case where:
// prefix: x/y/
// cursor: x/y/z/w
// In this case, we want the skip prefix to be `x/y/z` + string('/' + 1).
cursorWithoutPrefix := cursor.Key[len(prefix):]
p := strings.IndexByte(string(cursorWithoutPrefix), Delimiter)
if p < 0 {
// The cursor is not a prefix, but instead a path inside the prefix,
// so we can use it directly.
return iterateCursor{
Key: cursor.Key,
Version: cursor.Version,
}
}
// return the next prefix given a scoped path
return iterateCursor{
Key: cursor.Key[:len(prefix)+p] + ObjectKey(Delimiter+1),
Version: -1,
Inclusive: true,
}
}