Move the document changes sorting logic to a new trait

milli/src/update/new/indexer/document_operation.rs

@@ -6,6 +6,7 @@ use heed::types::Bytes;
 use heed::RoTxn;
 use memmap2::Mmap;
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
+use IndexDocumentsMethod as Idm;
 
 use super::super::document_change::DocumentChange;
 use super::super::items_pool::ItemsPool;
@@ -148,6 +149,8 @@ impl<'p, 'pl: 'p> DocumentChanges<'p> for DocumentOperation<'pl> {
                                     (docid, vec![document_operation]),
                                 );
                             }
+                            // TODO clean the code to make sure we clean the useless operations
+                            //      add a method to the MergeChanges trait
                             Some((_, offsets)) => offsets.push(document_operation),
                         }
 
@@ -185,16 +188,10 @@ impl<'p, 'pl: 'p> DocumentChanges<'p> for DocumentOperation<'pl> {
         // TODO We must drain the HashMap into a Vec because rayon::hash_map::IntoIter: !Clone
         let mut docids_version_offsets: Vec<_> = docids_version_offsets.drain().collect();
         // Reorder the offsets to make sure we iterate on the file sequentially
-        docids_version_offsets.sort_unstable_by_key(|(_, (_, offsets))| {
-            offsets
-                .iter()
-                .rev()
-                .find_map(|ido| match ido {
-                    InnerDocOp::Addition(add) => Some(add.content.as_ptr() as usize),
-                    InnerDocOp::Deletion => None,
-                })
-                .unwrap_or(0)
-        });
+        match self.index_documents_method {
+            Idm::ReplaceDocuments => MergeDocumentForReplacement::sort(&mut docids_version_offsets),
+            Idm::UpdateDocuments => MergeDocumentForUpdates::sort(&mut docids_version_offsets),
+        }
 
         Ok(docids_version_offsets
             .into_par_iter()
@@ -202,11 +199,9 @@ impl<'p, 'pl: 'p> DocumentChanges<'p> for DocumentOperation<'pl> {
                 Arc::new(ItemsPool::new(|| index.read_txn().map_err(crate::Error::from))),
                 move |context_pool, (external_docid, (internal_docid, operations))| {
                     context_pool.with(|rtxn| {
-                        use IndexDocumentsMethod as Idm;
-
                         let document_merge_function = match self.index_documents_method {
-                            Idm::ReplaceDocuments => merge_document_for_replacements,
-                            Idm::UpdateDocuments => merge_document_for_updates,
+                            Idm::ReplaceDocuments => MergeDocumentForReplacement::merge,
+                            Idm::UpdateDocuments => MergeDocumentForUpdates::merge,
                         };
 
                         document_merge_function(
@@ -224,10 +219,41 @@ impl<'p, 'pl: 'p> DocumentChanges<'p> for DocumentOperation<'pl> {
     }
 }
 
+trait MergeChanges {
+    /// Reorders the offsets to make sure we iterate on the file sequentially.
+    fn sort(changes_offsets: &mut [(CowStr, (DocumentId, Vec<InnerDocOp>))]);
+
+    fn merge(
+        rtxn: &RoTxn,
+        index: &Index,
+        fields_ids_map: &FieldsIdsMap,
+        docid: DocumentId,
+        external_docid: String,
+        operations: &[InnerDocOp],
+    ) -> Result<Option<DocumentChange>>;
+}
+
+struct MergeDocumentForReplacement;
+
+impl MergeChanges for MergeDocumentForReplacement {
+    /// Reorders to read only the last change.
+    fn sort(changes_offsets: &mut [(CowStr, (DocumentId, Vec<InnerDocOp>))]) {
+        changes_offsets.sort_unstable_by_key(|(_, (_, offsets))| {
+            offsets
+                .iter()
+                .rev()
+                .find_map(|ido| match ido {
+                    InnerDocOp::Addition(add) => Some(add.content.as_ptr() as usize),
+                    InnerDocOp::Deletion => None,
+                })
+                .unwrap_or(0)
+        });
+    }
+
     /// Returns only the most recent version of a document based on the updates from the payloads.
     ///
     /// This function is only meant to be used when doing a replacement and not an update.
-fn merge_document_for_replacements(
+    fn merge(
         rtxn: &RoTxn,
         index: &Index,
         fields_ids_map: &FieldsIdsMap,
@@ -276,12 +302,29 @@ fn merge_document_for_replacements(
             None => Ok(None), // but it's strange
         }
     }
+}
+
+struct MergeDocumentForUpdates;
+
+impl MergeChanges for MergeDocumentForUpdates {
+    /// Reorders to read the first changes first so that it's faster to read the first one and then the rest.
+    fn sort(changes_offsets: &mut [(CowStr, (DocumentId, Vec<InnerDocOp>))]) {
+        changes_offsets.sort_unstable_by_key(|(_, (_, offsets))| {
+            offsets
+                .iter()
+                .find_map(|ido| match ido {
+                    InnerDocOp::Addition(add) => Some(add.content.as_ptr() as usize),
+                    InnerDocOp::Deletion => None,
+                })
+                .unwrap_or(0)
+        });
+    }
 
     /// Reads the previous version of a document from the database, the new versions
     /// in the grenad update files and merges them to generate a new boxed obkv.
     ///
     /// This function is only meant to be used when doing an update and not a replacement.
-fn merge_document_for_updates(
+    fn merge(
         rtxn: &RoTxn,
         index: &Index,
         fields_ids_map: &FieldsIdsMap,
@@ -350,6 +393,7 @@ fn merge_document_for_updates(
             }
         }
     }
+}
 
 use std::borrow::Borrow;