feat: Introduce some stats to ease debugging

meilidb-data/src/database/documents_index.rs

@@ -44,6 +44,26 @@ impl DocumentsIndex {
 
         DocumentFieldsIter(iter, end.to_vec())
     }
+
+    pub fn len(&self) -> Result<usize, rocksdb::Error> {
+        let mut last_document_id = None;
+        let mut count = 0;
+
+        let from = rocksdb::IteratorMode::Start;
+        let iterator = self.0.iterator(from)?;
+
+        for (key, value) in iterator {
+            let slice = key.as_ref().try_into().unwrap();
+            let document_id = DocumentAttrKey::from_be_bytes(slice).document_id;
+
+            if Some(document_id) != last_document_id {
+                last_document_id = Some(document_id);
+                count += 1;
+            }
+        }
+
+        Ok(count)
+    }
 }
 
 pub struct DocumentFieldsIter<'a>(rocksdb::DBIterator<'a>, Vec<u8>);

meilidb-data/src/database/index.rs

@@ -15,6 +15,13 @@ use crate::serde::Deserializer;
 use super::{Error, CustomSettings};
 use super::{RawIndex, DocumentsAddition, DocumentsDeletion};
 
+#[derive(Copy, Clone)]
+pub struct IndexStats {
+    pub number_of_words: usize,
+    pub number_of_documents: usize,
+    pub number_attrs_in_ranked_map: usize,
+}
+
 #[derive(Clone)]
 pub struct Index(pub ArcSwap<InnerIndex>);
 
@@ -48,6 +55,16 @@ impl Index {
         Ok(index)
     }
 
+    pub fn stats(&self) -> Result<IndexStats, rocksdb::Error> {
+        let lease = self.0.lease();
+
+        Ok(IndexStats {
+            number_of_words: lease.words.len(),
+            number_of_documents: lease.raw.documents.len()?,
+            number_attrs_in_ranked_map: lease.ranked_map.len(),
+        })
+    }
+
     pub fn query_builder(&self) -> QueryBuilder<IndexLease> {
         let lease = IndexLease(self.0.lease());
         QueryBuilder::new(lease)

meilidb-data/src/ranked_map.rs

@@ -9,6 +9,10 @@ use crate::{SchemaAttr, Number};
 pub struct RankedMap(HashMap<(DocumentId, SchemaAttr), Number>);
 
 impl RankedMap {
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
     pub fn insert(&mut self, document: DocumentId, attribute: SchemaAttr, number: Number) {
         self.0.insert((document, attribute), number);
     }