Struct ColumnMeta 

pub struct ColumnMeta {
    pub name: String,
    pub data_type: u8,
    pub role: u8,
    pub default_encoding: u8,
    pub stats: ColumnStats,
    pub bloom_filter: Option<Vec<u8>>,
    pub encrypted: bool,
    pub key_id: Option<String>,
    pub row_group_blooms: Option<Vec<Vec<u8>>>,
}

Metadata for a single column within a segment.

Segment-level statistics

The stats field stores aggregate statistics across all row groups: min_value, max_value, null_count, value_count, sum, and distinct_count. These are computed by the segment writer during encoding and merged via merge_stats(). Query-time code can use these to prune entire segments without reading row-group data.

Metadata is kept proportional to the data: no fixed-size sketches or histograms, which cost ~49 KiB per segment however little it holds, and which the planner does not need — distinct_count above is exact.

Fields

name: String

Column name.

data_type: u8

Column data type tag (maps to ColumnType).

role: u8

Column role tag: 0 = timestamp, 1 = tag, 2 = field.

default_encoding: u8

The encoding the writer intended for this column, chosen from the column’s type before any data was seen.

This is a hint only. The adaptive selector may fall back to a different codec per block (e.g. Chimp → Gorilla → plain), so the authoritative encoding for reading is always ColumnBlockMeta::encoding. The field was previously named encoding, which read as a statement of fact; nothing decodes from it, but the name invited that mistake.

stats: ColumnStats

Global statistics across all row groups (min, max, null_count, value_count, sum, distinct_count). Enables segment-level pruning at query time.

bloom_filter: Option<Vec<u8>>

Bloom filter for tag columns.

Contains the serialized bloom filter bit array for tag columns, enabling segment-level predicate pushdown: if a queried tag value is definitely not in the bloom filter, the segment can be skipped. None for non-tag columns, and for segments written before per-tag row-group blooms existed.

encrypted: bool

Whether this column is encrypted at rest (field-level encryption).

When true, all column blocks for this column are AES-256-GCM encrypted and key_id identifies the encryption key. Statistics (min/max/sum/distinct) are zeroed to prevent leakage.

key_id: Option<String>

Encryption key ID for this column. Used by the reader to look up the decryption key from a FieldKeyProvider.

row_group_blooms: Option<Vec<Vec<u8>>>

Per-row-group bloom filters for string columns .

row_group_blooms[rg_idx] is a serialized bloom filter containing all distinct string values for this column in that row group. Enables row-group-level predicate pushdown: if a queried value is definitely not in the bloom filter, the row group can be skipped. None for non-string columns, encrypted columns, or segments written before .

Trait Implementations

impl Clone for ColumnMeta

fn clone(&self) -> ColumnMeta

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ColumnMeta

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ColumnMeta

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for ColumnMeta

fn eq(&self, other: &ColumnMeta) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for ColumnMeta

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ColumnMeta