Package org.elasticsearch.xpack.esql.datasources.spi

Interface IndexedDecompressionCodec

All Superinterfaces:

DecompressionCodec

public interface IndexedDecompressionCodec
extends DecompressionCodec

Extension of DecompressionCodec for codecs that support index-based random access to independently compressed frames. The canonical example is the Zstandard seekable format, which appends a seek table as a skippable frame at the end of the file.

When a codec implements this interface and an index is available for a given file, the split provider can create splits aligned to frame boundaries without scanning the compressed data for block markers. This is more efficient than SplittableDecompressionCodec for formats that embed their own index.

If no index is available (e.g. the file was compressed without seekable support), the codec falls back to stream-only decompression via DecompressionCodec.decompress(InputStream).

Method Summary

Modifier and Type	Method	Description
InputStream	decompressFrame(StorageObject object, long compressedOffset, long compressedLength)	Decompresses a single frame at the given compressed offset and length.
boolean	hasIndex(StorageObject object)	Checks whether the given storage object contains a frame index (e.g.
FrameIndex	readIndex(StorageObject object)	Reads the frame index from the storage object.

Methods inherited from interface org.elasticsearch.xpack.esql.datasources.spi.DecompressionCodec

decompress, extensions, name

Method Details

hasIndex

boolean hasIndex(StorageObject object)
          throws IOException

Checks whether the given storage object contains a frame index (e.g. a seek table appended as a skippable frame).

Throws:

IOException

readIndex

FrameIndex readIndex(StorageObject object)
              throws IOException

Reads the frame index from the storage object. The index describes the compressed offset, compressed size, and decompressed size of each independently decompressible frame.

Throws:

IOException - if the index cannot be read or is malformed

UnsupportedOperationException - if hasIndex(org.elasticsearch.xpack.esql.datasources.spi.StorageObject) returns false

decompressFrame

InputStream decompressFrame(StorageObject object,
 long compressedOffset,
 long compressedLength)
                     throws IOException

Decompresses a single frame at the given compressed offset and length. The returned stream yields the decompressed bytes for that frame only.

Parameters:

object - the storage object containing the compressed data

compressedOffset - byte offset of the frame in the compressed file

compressedLength - byte length of the compressed frame

Returns:

an input stream yielding decompressed bytes for the frame

Throws:

IOException