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Graph-based ranking rule + term matching strategy support

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This commit is contained in:
Loïc Lecrenier 2023-03-30 12:12:41 +02:00
parent aa9592455c
commit fdd02105ac
2 changed files with 185 additions and 211 deletions
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392
milli/src/search/new/graph_based_ranking_rule.rs
View File

@ -36,12 +36,11 @@ That is we find the documents where either:
- OR: `pretty` is 2-close to `house` AND `house` is 1-close to `by`
*/
use std::collections::HashSet;
use std::ops::ControlFlow;
use roaring::RoaringBitmap;
use super::interner::MappedInterner;
use super::interner::{Interned, MappedInterner};
use super::logger::SearchLogger;
use super::query_graph::QueryNode;
use super::ranking_rule_graph::{
@ -50,33 +49,35 @@ use super::ranking_rule_graph::{
};
use super::small_bitmap::SmallBitmap;
use super::{QueryGraph, RankingRule, RankingRuleOutput, SearchContext};
use crate::search::new::query_graph::QueryNodeData;
use crate::Result;
use crate::search::new::query_term::LocatedQueryTermSubset;
use crate::search::new::ranking_rule_graph::PathVisitor;
use crate::{Result, TermsMatchingStrategy};
pub type Proximity = GraphBasedRankingRule<ProximityGraph>;
impl Default for GraphBasedRankingRule<ProximityGraph> {
fn default() -> Self {
Self::new("proximity".to_owned())
impl GraphBasedRankingRule<ProximityGraph> {
pub fn new(terms_matching_strategy: Option<TermsMatchingStrategy>) -> Self {
Self::new_with_id("proximity".to_owned(), terms_matching_strategy)
}
}
pub type Typo = GraphBasedRankingRule<TypoGraph>;
impl Default for GraphBasedRankingRule<TypoGraph> {
fn default() -> Self {
Self::new("typo".to_owned())
impl GraphBasedRankingRule<TypoGraph> {
pub fn new(terms_matching_strategy: Option<TermsMatchingStrategy>) -> Self {
Self::new_with_id("typo".to_owned(), terms_matching_strategy)
}
}
/// A generic graph-based ranking rule
pub struct GraphBasedRankingRule<G: RankingRuleGraphTrait> {
id: String,
terms_matching_strategy: Option<TermsMatchingStrategy>,
// When the ranking rule is not iterating over its buckets,
// its state is `None`.
state: Option<GraphBasedRankingRuleState<G>>,
}
impl<G: RankingRuleGraphTrait> GraphBasedRankingRule<G> {
/// Creates the ranking rule with the given identifier
pub fn new(id: String) -> Self {
Self { id, state: None }
pub fn new_with_id(id: String, terms_matching_strategy: Option<TermsMatchingStrategy>) -> Self {
Self { id, terms_matching_strategy, state: None }
}
}
@ -89,7 +90,7 @@ pub struct GraphBasedRankingRuleState<G: RankingRuleGraphTrait> {
/// Cache used to optimistically discard paths that resolve to no documents.
dead_ends_cache: DeadEndsCache<G::Condition>,
/// A structure giving the list of possible costs from each node to the end node
all_distances: MappedInterner<QueryNode, Vec<u16>>,
all_costs: MappedInterner<QueryNode, Vec<u64>>,
/// An index in the first element of `all_distances`, giving the cost of the next bucket
cur_distance_idx: usize,
}
@ -105,18 +106,45 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
_universe: &RoaringBitmap,
query_graph: &QueryGraph,
) -> Result<()> {
let graph = RankingRuleGraph::build(ctx, query_graph.clone())?;
let removal_cost = if let Some(terms_matching_strategy) = self.terms_matching_strategy {
// oh no this is wrong!
// because
// skipping the second node should require that the first one be skipped too
match terms_matching_strategy {
TermsMatchingStrategy::Last => {
let removal_order =
query_graph.removal_order_for_terms_matching_strategy_last();
let mut forbidden_nodes =
SmallBitmap::for_interned_values_in(&query_graph.nodes);
let mut costs = query_graph.nodes.map(|_| None);
let mut cost = 100;
for ns in removal_order {
for n in ns.iter() {
*costs.get_mut(n) = Some((cost, forbidden_nodes.clone()));
}
forbidden_nodes.union(&ns);
cost = 1000;
}
costs
}
TermsMatchingStrategy::All => query_graph.nodes.map(|_| None),
}
} else {
query_graph.nodes.map(|_| None)
};
let graph = RankingRuleGraph::build(ctx, query_graph.clone(), removal_cost)?;
let condition_docids_cache = ConditionDocIdsCache::default();
let dead_ends_cache = DeadEndsCache::new(&graph.conditions_interner);
// Then pre-compute the cost of all paths from each node to the end node
let all_distances = graph.initialize_distances_with_necessary_edges();
let all_costs = graph.find_all_costs_to_end();
let state = GraphBasedRankingRuleState {
graph,
conditions_cache: condition_docids_cache,
dead_ends_cache,
all_distances,
all_costs,
cur_distance_idx: 0,
};
@ -140,16 +168,13 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
// If the cur_distance_idx does not point to a valid cost in the `all_distances`
// structure, then we have computed all the buckets and can return.
if state.cur_distance_idx
>= state.all_distances.get(state.graph.query_graph.root_node).len()
{
if state.cur_distance_idx >= state.all_costs.get(state.graph.query_graph.root_node).len() {
self.state = None;
return Ok(None);
}
// Retrieve the cost of the paths to compute
let cost =
state.all_distances.get(state.graph.query_graph.root_node)[state.cur_distance_idx];
let cost = state.all_costs.get(state.graph.query_graph.root_node)[state.cur_distance_idx];
state.cur_distance_idx += 1;
let mut bucket = RoaringBitmap::new();
@ -158,7 +183,7 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
graph,
conditions_cache: condition_docids_cache,
dead_ends_cache,
all_distances,
all_costs,
cur_distance_idx: _,
} = &mut state;
@ -167,8 +192,8 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
let original_graph = graph.clone();
let mut used_conditions = SmallBitmap::for_interned_values_in(&graph.conditions_interner);
let mut considered_paths = vec![];
let mut good_paths = vec![];
let mut considered_paths = vec![];
// For each path of the given cost, we will compute its associated
// document ids.
@ -176,168 +201,80 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
// and update the `dead_ends_cache` accordingly.
// Updating the dead_ends_cache helps speed up the execution of `visit_paths_of_cost` and reduces
// the number of future candidate paths given by that same function.
graph.visit_paths_of_cost(
graph.query_graph.root_node,
cost,
all_distances,
dead_ends_cache,
|path, graph, dead_ends_cache| {
if universe.is_empty() {
return Ok(ControlFlow::Break(()));
}
/* TODO: there are a couple ways to improve the speed of path computation.
let mut subpaths_docids: Vec<(Interned<G::Condition>, RoaringBitmap)> = vec![];
1. Since the `visit_paths_of_cost` method uses a depth-first-search, we know that
consecutive calls to this closure have a high chance of giving paths sharing
some prefix. It would be good to reuse `subpath_docids` and `visited_conditions`
to find out what this common prefix is, to avoid recomputing it. In a way, doing
this serves as the dual of the DeadEndsCache: it takes advantage of our knowledge that
some paths *aren't* deadends. There is however a subtlety in that the universe might
have changed between the two consecutive calls. This is why we should subtract the docids
of the previous path (if successful) to the `subpath_docids`, at the same time as we do
it for the universe.
2. We perform way too many intersections with the universe. For the first visited path,
the operation we do is essentially:
universe & (c1 & universe) & (c2 & universe) & (c3 & universe) & etc.
This is a good idea *only if the universe is very small*. But if the universe is (almost)
a superset of each condition, then these intersections serve no purpose and slow down the search.
Maybe in the future we have a `deserialize_within_universe` method, which would speed up
these intersections. But for now, we have to be careful.
3. We could know in advance how many paths of a certain cost exist, and only update the
DeadEndsCache if (m)any remaining paths exist. There is a subtlety here because
on the next call of `next_bucket`, we will want an updated and correct DeadEndsCache.
We need to think about that. We could also avoid putting forbidden edges in this cache
if we know, somehow, that we won't visit this edge again.
4. Finally, but that will be a long term difficult project. We should compute the path *lazily*.
That is, when we do `path_docids &= condition`. We shouldn't *actually* perform the intersection,
but simply register that operation. It's only when we ask if the path_docids is empty that
**the minimum amount of work to determine whether the path is empty** is carried out. In practice,
that means performing a MultiOps on each container, in order or not, until any resulting container
is found to be non-empty. (In fact, when we ask `is_empty`, we should probably find the container
that has the highest chance of being non-empty and compute that one first).
*/
// Accumulate the path for logging purposes only
considered_paths.push(path.to_vec());
let mut path_docids = universe.clone();
// We store the edges and their docids in vectors in case the path turns out to be
// empty and we need to figure out why it was empty.
let mut visited_conditions = vec![];
// let mut cached_condition_docids = vec![];
let mut subpath_docids = vec![];
for (latest_condition_path_idx, &latest_condition) in path.iter().enumerate() {
visited_conditions.push(latest_condition);
let condition_docids = condition_docids_cache.get_condition_docids(
ctx,
latest_condition,
graph,
&universe,
)?;
// If the edge is empty, then the path will be empty as well, we update the graph
// and caches accordingly and skip to the next candidate path.
if condition_docids.is_empty() {
// 1. Store in the cache that this edge is empty for this universe
dead_ends_cache.forbid_condition(latest_condition);
// 2. remove all the edges with this condition from the ranking rule graph
graph.remove_edges_with_condition(latest_condition);
return Ok(ControlFlow::Continue(()));
}
path_docids &= condition_docids;
subpath_docids.push(path_docids.clone());
// If the (sub)path is empty, we try to figure out why and update the caches accordingly.
if path_docids.is_empty() {
let len_prefix = subpath_docids.len() - 1;
// First, we know that this path is empty, and thus any path
// that is a superset of it will also be empty.
dead_ends_cache.forbid_condition_after_prefix(
visited_conditions[..len_prefix].iter().copied(),
latest_condition,
);
if visited_conditions.len() > 1 {
let mut subprefix = vec![];
// Deadend if the intersection between this edge and any
// previous prefix is disjoint with the universe
for (past_condition, subpath_docids) in visited_conditions[..len_prefix]
.iter()
.zip(subpath_docids[..len_prefix].iter())
{
if *past_condition == latest_condition {
todo!();
};
subprefix.push(*past_condition);
if condition_docids.is_disjoint(subpath_docids) {
dead_ends_cache.forbid_condition_after_prefix(
subprefix.iter().copied(),
latest_condition,
);
}
}
// keep the same prefix and check the intersection with
// all the remaining conditions
let mut forbidden = dead_ends_cache.forbidden.clone();
let mut cursor = dead_ends_cache;
for &c in visited_conditions[..len_prefix].iter() {
cursor = cursor.advance(c).unwrap();
forbidden.union(&cursor.forbidden);
}
let past_path_docids = &subpath_docids[subpath_docids.len() - 2];
let remaining_conditions =
path[latest_condition_path_idx..].iter().skip(1);
for next_condition in remaining_conditions {
if forbidden.contains(*next_condition) {
continue;
}
let next_condition_docids = condition_docids_cache
.get_condition_docids(ctx, *next_condition, graph, &universe)?;
if past_path_docids.is_disjoint(next_condition_docids) {
cursor.forbid_condition(*next_condition);
}
}
}
return Ok(ControlFlow::Continue(()));
let visitor = PathVisitor::new(cost, graph, all_costs, dead_ends_cache);
visitor.visit_paths(&mut |path, graph, dead_ends_cache| {
considered_paths.push(path.to_vec());
// If the universe is empty, stop exploring the graph, since no docids will ever be found anymore.
if universe.is_empty() {
return Ok(ControlFlow::Break(()));
}
// `visit_paths` performs a depth-first search, so the previously visited path
// is likely to share a prefix with the current one.
// We stored the previous path and the docids associated to each of its prefixes in `subpaths_docids`.
// We take advantage of this to avoid computing the docids associated with the common prefix between
// the old and current path.
let idx_of_first_different_condition = {
let mut idx = 0;
for (&last_c, cur_c) in path.iter().zip(subpaths_docids.iter().map(|x| x.0)) {
if last_c == cur_c {
idx += 1;
} else {
break;
}
}
assert!(!path_docids.is_empty());
// Accumulate the path for logging purposes only
good_paths.push(path.to_vec());
for condition in path {
used_conditions.insert(*condition);
subpaths_docids.truncate(idx);
idx
};
// Then for the remaining of the path, we continue computing docids.
for latest_condition in path[idx_of_first_different_condition..].iter().copied() {
// The visit_path_condition will stop
let success = visit_path_condition(
ctx,
graph,
&universe,
dead_ends_cache,
condition_docids_cache,
&mut subpaths_docids,
latest_condition,
)?;
if !success {
return Ok(ControlFlow::Continue(()));
}
bucket |= &path_docids;
// Reduce the size of the universe so that we can more optimistically discard candidate paths
universe -= path_docids;
}
assert!(subpaths_docids.iter().map(|x| x.0).eq(path.iter().copied()));
let path_docids =
subpaths_docids.pop().map(|x| x.1).unwrap_or_else(|| universe.clone());
assert!(!path_docids.is_empty());
// Accumulate the path for logging purposes only
good_paths.push(path.to_vec());
for &condition in path {
used_conditions.insert(condition);
}
bucket |= &path_docids;
// Reduce the size of the universe so that we can more optimistically discard candidate paths
universe -= &path_docids;
for (_, docids) in subpaths_docids.iter_mut() {
*docids -= &path_docids;
}
if universe.is_empty() {
Ok(ControlFlow::Break(()))
} else {
Ok(ControlFlow::Continue(()))
}
})?;
if universe.is_empty() {
Ok(ControlFlow::Break(()))
} else {
Ok(ControlFlow::Continue(()))
}
},
)?;
// println!(" {} paths of cost {} in {}", paths.len(), cost, self.id);
G::log_state(
&original_graph,
&good_paths,
&considered_paths,
dead_ends_cache,
original_universe,
all_distances,
all_costs,
cost,
logger,
);
@ -346,40 +283,21 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
// that was used to compute this bucket
// But we only do it in case the bucket length is >1, because otherwise
// we know the child ranking rule won't be called anyway
let mut next_query_graph = original_graph.query_graph;
if bucket.len() > 1 {
next_query_graph.simplify();
// 1. Gather all the words and phrases used in the computation of this bucket
let mut used_words = HashSet::new();
let mut used_phrases = HashSet::new();
for condition in used_conditions.iter() {
let (ws, ps) =
condition_docids_cache.get_condition_used_words_and_phrases(condition);
used_words.extend(ws);
used_phrases.extend(ps);
}
// 2. Remove the unused words and phrases from all the nodes in the graph
let mut nodes_to_remove = vec![];
for (node_id, node) in next_query_graph.nodes.iter_mut() {
let term = match &mut node.data {
QueryNodeData::Term(term) => term,
QueryNodeData::Deleted | QueryNodeData::Start | QueryNodeData::End => continue,
};
if let Some(new_term) = ctx
.term_interner
.get(term.value)
.removing_forbidden_terms(&used_words, &used_phrases)
{
if new_term.is_empty() {
nodes_to_remove.push(node_id);
} else {
term.value = ctx.term_interner.push(new_term);
}
}
}
// 3. Remove the empty nodes from the graph
next_query_graph.remove_nodes(&nodes_to_remove);
}
let paths: Vec<Vec<(Option<LocatedQueryTermSubset>, LocatedQueryTermSubset)>> = good_paths
.into_iter()
.map(|path| {
path.into_iter()
.map(|condition| {
let (a, b) =
condition_docids_cache.get_subsets_used_by_condition(condition);
(a.clone(), b.clone())
})
.collect()
})
.collect();
let next_query_graph = QueryGraph::build_from_paths(paths);
self.state = Some(state);
@ -394,3 +312,59 @@ impl<'ctx, G: RankingRuleGraphTrait> RankingRule<'ctx, QueryGraph> for GraphBase
self.state = None;
}
}
/// Returns false if the intersection between the condition
/// docids and the previous path docids is empty.
fn visit_path_condition<G: RankingRuleGraphTrait>(
ctx: &mut SearchContext,
graph: &mut RankingRuleGraph<G>,
universe: &RoaringBitmap,
dead_ends_cache: &mut DeadEndsCache<G::Condition>,
condition_docids_cache: &mut ConditionDocIdsCache<G>,
subpath: &mut Vec<(Interned<G::Condition>, RoaringBitmap)>,
latest_condition: Interned<G::Condition>,
) -> Result<bool> {
let condition_docids = &condition_docids_cache
.get_computed_condition(ctx, latest_condition, graph, universe)?
.docids;
if condition_docids.is_empty() {
// 1. Store in the cache that this edge is empty for this universe
dead_ends_cache.forbid_condition(latest_condition);
// 2. remove all the edges with this condition from the ranking rule graph
graph.remove_edges_with_condition(latest_condition);
return Ok(false);
}
let latest_path_docids = if let Some((_, prev_docids)) = subpath.last() {
prev_docids & condition_docids
} else {
condition_docids.clone()
};
if !latest_path_docids.is_empty() {
subpath.push((latest_condition, latest_path_docids));
return Ok(true);
}
// If the (sub)path is empty, we try to figure out why and update the caches accordingly.
// First, we know that this path is empty, and thus any path
// that is a superset of it will also be empty.
dead_ends_cache.forbid_condition_after_prefix(subpath.iter().map(|x| x.0), latest_condition);
if subpath.len() <= 1 {
return Ok(false);
}
let mut subprefix = vec![];
// Deadend if the intersection between this edge and any
// previous prefix is disjoint with the universe
// We already know that the intersection with the last one
// is empty,
for (past_condition, sp_docids) in subpath[..subpath.len() - 1].iter() {
subprefix.push(*past_condition);
if condition_docids.is_disjoint(sp_docids) {
dead_ends_cache
.forbid_condition_after_prefix(subprefix.iter().copied(), latest_condition);
}
}
Ok(false)
}

4
milli/src/search/new/mod.rs
View File

@ -198,14 +198,14 @@ fn get_ranking_rules_for_query_graph_search<'ctx>(
continue;
}
typo = true;
ranking_rules.push(Box::<Typo>::default());
ranking_rules.push(Box::new(Typo::new(None)));
}
crate::Criterion::Proximity => {
if proximity {
continue;
}
proximity = true;
ranking_rules.push(Box::<Proximity>::default());
ranking_rules.push(Box::new(Proximity::new(None)));
}
crate::Criterion::Attribute => {
if attribute {