From b7ed22bc5995af551b9384659a5147e633580a74 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Renault?= <renault.cle@gmail.com>
Date: Mon, 24 Jun 2019 17:29:14 +0200
Subject: [PATCH] feat: Introduce on the fly attributes reordering with
 meilidb-core

---
 meilidb-core/src/lib.rs             |  1 +
 meilidb-core/src/query_builder.rs   | 13 ++++++++-----
 meilidb-core/src/reordered_attrs.rs | 20 ++++++++++++++++++++
 3 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 meilidb-core/src/reordered_attrs.rs

diff --git a/meilidb-core/src/lib.rs b/meilidb-core/src/lib.rs
index 72435ea46..9c1c1c88d 100644
--- a/meilidb-core/src/lib.rs
+++ b/meilidb-core/src/lib.rs
@@ -4,6 +4,7 @@
 mod automaton;
 mod distinct_map;
 mod query_builder;
+mod reordered_attrs;
 mod store;
 pub mod criterion;
 
diff --git a/meilidb-core/src/query_builder.rs b/meilidb-core/src/query_builder.rs
index b02caa30c..63d39c1d2 100644
--- a/meilidb-core/src/query_builder.rs
+++ b/meilidb-core/src/query_builder.rs
@@ -17,6 +17,7 @@ use crate::automaton::{build_dfa, build_prefix_dfa};
 use crate::distinct_map::{DistinctMap, BufferedDistinctMap};
 use crate::criterion::Criteria;
 use crate::raw_documents_from_matches;
+use crate::reordered_attrs::ReorderedAttrs;
 use crate::{Match, DocumentId, Store, RawDocument, Document};
 
 const NGRAMS: usize = 3;
@@ -193,7 +194,7 @@ fn rewrite_matched_positions(matches: &mut [(DocumentId, Match)]) {
 pub struct QueryBuilder<'c, S, FI = fn(DocumentId) -> bool> {
     store: S,
     criteria: Criteria<'c>,
-    searchable_attrs: Option<HashSet<u16>>,
+    searchable_attrs: Option<ReorderedAttrs>,
     filter: Option<FI>,
 }
 
@@ -228,8 +229,8 @@ impl<'c, S, FI> QueryBuilder<'c, S, FI>
     }
 
     pub fn add_searchable_attribute(&mut self, attribute: u16) {
-        let attributes = self.searchable_attrs.get_or_insert_with(HashSet::new);
-        attributes.insert(attribute);
+        let reorders = self.searchable_attrs.get_or_insert_with(Default::default);
+        reorders.insert_attribute(attribute);
     }
 }
 
@@ -239,6 +240,7 @@ where S: Store,
     fn query_all(&self, query: &str) -> Result<Vec<RawDocument>, S::Error> {
         let automatons = generate_automatons(query, &self.store)?;
         let words = self.store.words()?.as_fst();
+        let searchables = self.searchable_attrs.as_ref();
 
         let mut stream = {
             let mut op_builder = fst::raw::OpBuilder::new();
@@ -264,11 +266,12 @@ where S: Store,
                 };
 
                 for di in doc_indexes.as_slice() {
-                    if self.searchable_attrs.as_ref().map_or(true, |r| r.contains(&di.attribute)) {
+                    let attribute = searchables.map_or(Some(di.attribute), |r| r.get(di.attribute));
+                    if let Some(attribute) = attribute {
                         let match_ = Match {
                             query_index: query_index as u32,
                             distance,
-                            attribute: di.attribute,
+                            attribute,
                             word_index: di.word_index,
                             is_exact,
                             char_index: di.char_index,
diff --git a/meilidb-core/src/reordered_attrs.rs b/meilidb-core/src/reordered_attrs.rs
new file mode 100644
index 000000000..5b1567d1d
--- /dev/null
+++ b/meilidb-core/src/reordered_attrs.rs
@@ -0,0 +1,20 @@
+#[derive(Default)]
+pub struct ReorderedAttrs {
+    count: usize,
+    reorders: Vec<Option<u16>>,
+}
+
+impl ReorderedAttrs {
+    pub fn insert_attribute(&mut self, attribute: u16) {
+        self.reorders.resize(attribute as usize + 1, None);
+        self.reorders[attribute as usize] = Some(self.count as u16);
+        self.count += 1;
+    }
+
+    pub fn get(&self, attribute: u16) -> Option<u16> {
+        match self.reorders.get(attribute as usize) {
+            Some(Some(attribute)) => Some(*attribute),
+            _ => None,
+        }
+    }
+}