244 lines
8.3 KiB
Rust
244 lines
8.3 KiB
Rust
use std::collections::{BTreeMap, HashSet};
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use std::ops::Bound::Unbounded;
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use std::{cmp, fmt};
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use heed::types::{ByteSlice, Unit};
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use heed::{BytesDecode, Database};
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use roaring::RoaringBitmap;
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use crate::error::FieldIdMapMissingEntry;
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use crate::facet::FacetType;
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use crate::heed_codec::facet::FacetValueStringCodec;
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use crate::search::facet::{FacetIter, FacetRange};
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use crate::{DocumentId, FieldId, Index, Result};
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/// The default number of values by facets that will
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/// be fetched from the key-value store.
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const DEFAULT_VALUES_BY_FACET: usize = 100;
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/// The hard limit in the number of values by facets that will be fetched from
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/// the key-value store. Searching for more values could slow down the engine.
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const MAX_VALUES_BY_FACET: usize = 1000;
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/// Threshold on the number of candidates that will make
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/// the system to choose between one algorithm or another.
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const CANDIDATES_THRESHOLD: u64 = 1000;
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pub struct FacetDistribution<'a> {
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facets: Option<HashSet<String>>,
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candidates: Option<RoaringBitmap>,
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max_values_by_facet: usize,
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rtxn: &'a heed::RoTxn<'a>,
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index: &'a Index,
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}
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impl<'a> FacetDistribution<'a> {
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pub fn new(rtxn: &'a heed::RoTxn, index: &'a Index) -> FacetDistribution<'a> {
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FacetDistribution {
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facets: None,
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candidates: None,
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max_values_by_facet: DEFAULT_VALUES_BY_FACET,
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rtxn,
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index,
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}
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}
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pub fn facets<I: IntoIterator<Item = A>, A: AsRef<str>>(&mut self, names: I) -> &mut Self {
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self.facets = Some(names.into_iter().map(|s| s.as_ref().to_string()).collect());
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self
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}
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pub fn candidates(&mut self, candidates: RoaringBitmap) -> &mut Self {
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self.candidates = Some(candidates);
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self
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}
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pub fn max_values_by_facet(&mut self, max: usize) -> &mut Self {
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self.max_values_by_facet = cmp::min(max, MAX_VALUES_BY_FACET);
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self
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}
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/// There is a small amount of candidates OR we ask for facet string values so we
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/// decide to iterate over the facet values of each one of them, one by one.
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fn facet_distribution_from_documents(
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&self,
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field_id: FieldId,
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facet_type: FacetType,
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candidates: &RoaringBitmap,
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distribution: &mut BTreeMap<String, u64>,
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) -> heed::Result<()> {
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fn fetch_facet_values<'t, KC, K: 't>(
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rtxn: &'t heed::RoTxn,
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db: Database<KC, Unit>,
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field_id: FieldId,
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candidates: &RoaringBitmap,
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distribution: &mut BTreeMap<String, u64>,
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) -> heed::Result<()>
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where
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K: fmt::Display,
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KC: BytesDecode<'t, DItem = (FieldId, DocumentId, K)>,
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{
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let mut key_buffer = vec![field_id];
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for docid in candidates.into_iter().take(CANDIDATES_THRESHOLD as usize) {
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key_buffer.truncate(1);
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key_buffer.extend_from_slice(&docid.to_be_bytes());
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let iter = db
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.remap_key_type::<ByteSlice>()
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.prefix_iter(rtxn, &key_buffer)?
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.remap_key_type::<KC>();
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for result in iter {
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let ((_, _, value), ()) = result?;
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*distribution.entry(value.to_string()).or_insert(0) += 1;
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}
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}
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Ok(())
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}
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match facet_type {
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FacetType::Number => {
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let db = self.index.field_id_docid_facet_f64s;
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fetch_facet_values(self.rtxn, db, field_id, candidates, distribution)
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}
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FacetType::String => {
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let db = self.index.field_id_docid_facet_strings;
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fetch_facet_values(self.rtxn, db, field_id, candidates, distribution)
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}
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}
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}
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/// There is too much documents, we use the facet levels to move throught
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/// the facet values, to find the candidates and values associated.
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fn facet_numbers_distribution_from_facet_levels(
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&self,
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field_id: FieldId,
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candidates: &RoaringBitmap,
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distribution: &mut BTreeMap<String, u64>,
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) -> heed::Result<()> {
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let iter =
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FacetIter::new_non_reducing(self.rtxn, self.index, field_id, candidates.clone())?;
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for result in iter {
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let (value, mut docids) = result?;
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docids.intersect_with(candidates);
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if !docids.is_empty() {
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distribution.insert(value.to_string(), docids.len());
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}
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if distribution.len() == self.max_values_by_facet {
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break;
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}
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}
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Ok(())
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}
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/// Placeholder search, a.k.a. no candidates were specified. We iterate throught the
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/// facet values one by one and iterate on the facet level 0 for numbers.
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fn facet_values_from_raw_facet_database(
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&self,
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field_id: FieldId,
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) -> heed::Result<BTreeMap<String, u64>> {
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let mut distribution = BTreeMap::new();
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let db = self.index.facet_id_f64_docids;
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let range = FacetRange::new(self.rtxn, db, field_id, 0, Unbounded, Unbounded)?;
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for result in range {
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let ((_, _, value, _), docids) = result?;
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distribution.insert(value.to_string(), docids.len());
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if distribution.len() == self.max_values_by_facet {
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break;
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}
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}
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let iter = self
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.index
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.facet_id_string_docids
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.remap_key_type::<ByteSlice>()
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.prefix_iter(self.rtxn, &[field_id])?
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.remap_key_type::<FacetValueStringCodec>();
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for result in iter {
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let ((_, value), docids) = result?;
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distribution.insert(value.to_string(), docids.len());
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if distribution.len() == self.max_values_by_facet {
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break;
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}
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}
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Ok(distribution)
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}
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fn facet_values(&self, field_id: FieldId) -> heed::Result<BTreeMap<String, u64>> {
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use FacetType::{Number, String};
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if let Some(candidates) = self.candidates.as_ref() {
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// Classic search, candidates were specified, we must return facet values only related
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// to those candidates. We also enter here for facet strings for performance reasons.
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let mut distribution = BTreeMap::new();
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if candidates.len() <= CANDIDATES_THRESHOLD {
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self.facet_distribution_from_documents(
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field_id,
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Number,
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candidates,
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&mut distribution,
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)?;
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self.facet_distribution_from_documents(
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field_id,
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String,
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candidates,
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&mut distribution,
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)?;
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} else {
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self.facet_numbers_distribution_from_facet_levels(
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field_id,
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candidates,
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&mut distribution,
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)?;
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self.facet_distribution_from_documents(
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field_id,
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String,
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candidates,
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&mut distribution,
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)?;
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}
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Ok(distribution)
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} else {
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self.facet_values_from_raw_facet_database(field_id)
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}
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}
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pub fn execute(&self) -> Result<BTreeMap<String, BTreeMap<String, u64>>> {
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let fields_ids_map = self.index.fields_ids_map(self.rtxn)?;
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let filterable_fields = self.index.filterable_fields(self.rtxn)?;
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let mut distribution = BTreeMap::new();
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for name in filterable_fields {
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let fid =
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fields_ids_map.id(&name).ok_or_else(|| FieldIdMapMissingEntry::FieldName {
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field_name: name.clone(),
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process: "FacetDistribution::execute",
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})?;
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let values = self.facet_values(fid)?;
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distribution.insert(name, values);
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}
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Ok(distribution)
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}
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}
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impl fmt::Debug for FacetDistribution<'_> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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let FacetDistribution { facets, candidates, max_values_by_facet, rtxn: _, index: _ } = self;
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f.debug_struct("FacetDistribution")
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.field("facets", facets)
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.field("candidates", candidates)
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.field("max_values_by_facet", max_values_by_facet)
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.finish()
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}
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}
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