lance_encoding/
constants.rs

1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: Copyright The Lance Authors
3
4//! Constants for Lance encoding metadata keys
5//!
6//! These constants define the metadata keys used in Arrow field metadata
7//! to configure various encoding behaviors in Lance.
8
9// Compression-related metadata keys
10/// Metadata key for specifying compression scheme (e.g., "lz4", "zstd", "none")
11pub const COMPRESSION_META_KEY: &str = "lance-encoding:compression";
12/// Metadata key for specifying compression level (applies to schemes that support levels)
13pub const COMPRESSION_LEVEL_META_KEY: &str = "lance-encoding:compression-level";
14/// Metadata key for specifying RLE (Run-Length Encoding) threshold
15pub const RLE_THRESHOLD_META_KEY: &str = "lance-encoding:rle-threshold";
16
17// Dictionary encoding metadata keys
18/// Metadata key for specifying dictionary encoding threshold divisor
19pub const DICT_DIVISOR_META_KEY: &str = "lance-encoding:dict-divisor";
20
21// NOTE: BLOB_META_KEY is defined in lance-core to avoid circular dependency
22
23// Packed struct encoding metadata keys
24/// Legacy metadata key for packed struct encoding (deprecated)
25pub const PACKED_STRUCT_LEGACY_META_KEY: &str = "packed";
26/// Metadata key for packed struct encoding
27pub const PACKED_STRUCT_META_KEY: &str = "lance-encoding:packed";
28
29// Structural encoding metadata keys
30/// Metadata key for specifying structural encoding type
31pub const STRUCTURAL_ENCODING_META_KEY: &str = "lance-encoding:structural-encoding";
32/// Value for miniblock structural encoding
33pub const STRUCTURAL_ENCODING_MINIBLOCK: &str = "miniblock";
34/// Value for fullzip structural encoding
35pub const STRUCTURAL_ENCODING_FULLZIP: &str = "fullzip";
36
37// Byte stream split metadata keys
38/// Metadata key for byte stream split encoding configuration
39pub const BSS_META_KEY: &str = "lance-encoding:bss";
40/// Default BSS mode
41pub const DEFAULT_BSS_MODE: &str = "auto";