tantivy/src/termdict/mod.rs

//! The term dictionary main role is to associate the sorted [`Term`s](crate::Term) to
//! a [`TermInfo`](crate::postings::TermInfo) struct that contains some meta-information
//! about the term.
//!
//! Internally, the term dictionary relies on the `fst` crate to store
//! a sorted mapping that associate each term to its rank in the lexicographical order.
//! For instance, in a dictionary containing the sorted terms "abba", "bjork", "blur" and "donovan",
//! the [`TermOrdinal`] are respectively `0`, `1`, `2`, and `3`.
//!
//! For `u64`-terms, tantivy explicitly uses a `BigEndian` representation to ensure that the
//! lexicographical order matches the natural order of integers.
//!
//! `i64`-terms are transformed to `u64` using a continuous mapping `val ⟶ val - i64::MIN`
//! and then treated as a `u64`.
//!
//! `f64`-terms are transformed to `u64` using a mapping that preserve order, and are then treated
//! as `u64`.
//!
//! A second datastructure makes it possible to access a
//! [`TermInfo`](crate::postings::TermInfo).

#[cfg(not(feature = "quickwit"))]
mod fst_termdict;
#[cfg(not(feature = "quickwit"))]
use fst_termdict as termdict;

#[cfg(feature = "quickwit")]
mod sstable_termdict;
#[cfg(feature = "quickwit")]
use sstable_termdict as termdict;

#[cfg(test)]
mod tests;

/// Position of the term in the sorted list of terms.
pub type TermOrdinal = u64;

pub use self::termdict::{TermDictionary, TermDictionaryBuilder, TermMerger, TermStreamer};