IterateChangeSets iterate the change set files,.

IterateVersions iterate the version numbers in change set files, skipping the change set payloads.

ReadChangeSet decode a version of change set from reader.

ReadFirstVersion parse the first version number in the change set file.

SortFilesByFirstVerson parse the first version of the change set files and associate with the file name, then sort them by version number, also filter out empty files.

WrapReader wraps reader and closer together to create a new io.ReadCloser.

WriteChangeSet writes a version of change sets to writer.

SizeKeyLength is the number of bytes used to encode key length in sort payload.

We creates the temporary sst files in the target database to make sure the file renaming is cheap in ingestion part.

Options defines the customizable settings of ChangeSetGroupCmd.

ReadCloser combines `Reader` and `io.Closer`.

Reader combines `io.Reader` and `io.ByteReader`.