Module dictionary 

Dictionary encoding for string compression.

Dictionary encoding replaces repeated string values with integer codes, which is efficient for strings with low cardinality (many repeated values).

Example

let mut builder = DictionaryBuilder::new();
builder.add("apple");
builder.add("banana");
builder.add("apple");  // repeated
builder.add("cherry");
builder.add("apple");  // repeated

let dict = builder.build();
// Dictionary: ["apple", "banana", "cherry"]
// Encoded: [0, 1, 0, 2, 0]

Structs

DictionaryBuilder

Builder for creating dictionary encodings.

DictionaryEncoding

A dictionary-encoded string column.

Traits

IntoDictionaryEncoding

Extension trait for building dictionary encodings from iterators.