Encodings

Encoding turns a sequence of typed values into a byte stream before compression. The Chunk Header records the selected codec in encoding_type. This field describes values in a Value or non-aligned Chunk, and timestamps in an aligned Time Chunk.

Value	Name
0	PLAIN
1	DICTIONARY
2	RLE
3	DIFF
4	TS_2DIFF
5	BITMAP
6	GORILLA_V1
7	REGULAR
8	GORILLA
9	ZIGZAG
10	FREQ (deprecated)
11	CHIMP
12	SPRINTZ
13	RLBE
14	CAMEL

The following combinations are supported by the reference value encoders. An assigned codec number does not mean that every data type can use it:

Data type	Available encodings
BOOLEAN	PLAIN, RLE
INT32, INT64, TIMESTAMP, DATE	PLAIN, RLE, TS_2DIFF, GORILLA, ZIGZAG, CHIMP, SPRINTZ, RLBE
FLOAT	PLAIN, RLE, TS_2DIFF, GORILLA_V1, GORILLA, CHIMP, SPRINTZ, RLBE
DOUBLE	PLAIN, RLE, TS_2DIFF, GORILLA_V1, GORILLA, CHIMP, SPRINTZ, RLBE, CAMEL
TEXT, STRING	PLAIN, DICTIONARY
BLOB, OBJECT	PLAIN

Encoding Families

The identifiers describe different ways to transform a logical sequence into bytes. They are wire format identifiers, not implementation-specific enumeration ordinals.

Family	Encodings	Data property typically exploited
Literal	PLAIN	No prediction; values are serialized independently
Dictionary	DICTIONARY	Repeated binary values are replaced by dictionary references
Run length / bit packing	RLE, RLBE	Repeated values or small bit widths
Delta and prediction	DIFF, TS_2DIFF, REGULAR, SPRINTZ	Small or regular changes between adjacent values
Integer remapping	ZIGZAG	Small signed integers represented as small unsigned integers
XOR-based	GORILLA_V1, GORILLA, CHIMP, CAMEL	Stable leading and trailing bits between adjacent floating-point values
Legacy or specialized	BITMAP, FREQ	Reserved historical layouts; FREQ is deprecated

Different distributions favor different encodings. Whatever the writer chooses, the reader selects a decoder from the pair (data_type, encoding_type).

Plain Encoding

A PLAIN stream does not store an element count. The Page context, time stream, or null bitmap determines the number of elements. Values are written consecutively:

Data type	Encoding of one value
BOOLEAN	0x00 or 0x01
INT32, DATE	VarInt
INT64, TIMESTAMP	Big-endian int64
FLOAT	Big-endian float32
DOUBLE	Big-endian float64
TEXT, STRING, BLOB, OBJECT	VarInt byte_length + raw bytes

The length of a PLAIN binary value is non-negative. A non-aligned value stream does not contain nulls; the Value Page bitmap represents nulls in an aligned value stream.

The other encoding identifiers select their respective value-stream bit layouts. A reader cannot decode an unknown encoding as PLAIN.

Decoder Contract

A decoder's state lasts for one Page stream. After decryption and decompression, select the codec, decode within the stream boundary, and check that the number of values matches the Page context. Start with fresh decoding state for the next Page.

For aligned data, the Time Chunk Header names the time codec; an aligned Value Page decodes one value for each set bitmap bit. For non-aligned data, the Chunk Header names only the value codec. Its time codec comes from shared configuration, defaulting to TS_2DIFF; there is no serialized time_encoder footer field. See Configurations.

An unsupported encoding prevents value decoding. A scanner that parses the raw Header fields can still locate the next Chunk using data_size, even if a higher-level codec registry rejects the identifier. It must not substitute PLAIN or another decoder.