Merge #747

747: Soft-deletion computation no longer depends on the mapsize r=irevoire a=dureuill

# Pull Request

## Related issue

Related to meilisearch/meilisearch#3231: After removing `--max-index-size`, the `mapsize` will always be unrelated to the actual max size the user wants for their DB, so it doesn't make sense to use these values any longer.

This implements solution 2.3 from meilisearch/meilisearch#3231 (comment)

## What does this PR do?

### User-visible

- Soft-deleted are no longer deleted when there is less than 10% of the mapsize available or when they take more than 10% of the mapsize
- Instead, they are deleted when they are more soft deleted than regular documents, or when they take more than 1GiB disk space (estimated).

### Implementation standpoint

1. Adds a `DeletionStrategy` struct to replace the boolean `disable_soft_deletion` that we had up until now. This enum allows us to specify that we want "always hard", "always soft", or to use the dynamic soft-deletion strategy (default).
2. Uses the current strategy when deleting documents, with the new heuristics being used in the `DeletionStrategy::Dynamic` variant.
3. Updates the tests to use the appropriate DeletionStrategy whenever needed (one of `AlwaysHard` or `AlwaysSoft` depending on the test)

Note to reviewers: this PR is optimized for a commit-by-commit review.

## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!


Co-authored-by: Louis Dureuil <louis@meilisearch.com>
Co-authored-by: Tamo <tamo@meilisearch.com>

Author: 3 people

milli/src/index.rs

@@ -1192,8 +1192,8 @@ pub(crate) mod tests {
     use crate::error::{Error, InternalError};
     use crate::index::{DEFAULT_MIN_WORD_LEN_ONE_TYPO, DEFAULT_MIN_WORD_LEN_TWO_TYPOS};
     use crate::update::{
-        self, DeleteDocuments, IndexDocuments, IndexDocumentsConfig, IndexDocumentsMethod,
-        IndexerConfig, Settings,
+        self, DeleteDocuments, DeletionStrategy, IndexDocuments, IndexDocumentsConfig,
+        IndexDocumentsMethod, IndexerConfig, Settings,
     };
     use crate::{db_snap, obkv_to_json, Index};
 
@@ -1282,6 +1282,17 @@ pub(crate) mod tests {
             builder.execute(drop, || false)?;
             Ok(())
         }
+
+        pub fn delete_document(&self, external_document_id: &str) {
+            let mut wtxn = self.write_txn().unwrap();
+
+            let mut delete = DeleteDocuments::new(&mut wtxn, &self).unwrap();
+            delete.strategy(self.index_documents_config.deletion_strategy);
+
+            delete.delete_external_id(external_document_id);
+            delete.execute().unwrap();
+            wtxn.commit().unwrap();
+        }
     }
 
     #[test]
@@ -1487,7 +1498,9 @@ pub(crate) mod tests {
         use big_s::S;
         use maplit::hashset;
 
-        let index = TempIndex::new();
+        let mut index = TempIndex::new();
+        index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysSoft;
+        let index = index;
 
         index
             .update_settings(|settings| {
@@ -1657,7 +1670,8 @@ pub(crate) mod tests {
         }
         // Second Batch: replace the documents with soft-deletion
         {
-            index.index_documents_config.disable_soft_deletion = false;
+            index.index_documents_config.deletion_strategy =
+                crate::update::DeletionStrategy::AlwaysSoft;
             let mut docs1 = vec![];
             for i in 0..3 {
                 docs1.push(serde_json::json!(
@@ -1726,7 +1740,7 @@ pub(crate) mod tests {
         drop(rtxn);
         // Third Batch: replace the documents with soft-deletion again
         {
-            index.index_documents_config.disable_soft_deletion = false;
+            index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysSoft;
             let mut docs1 = vec![];
             for i in 0..3 {
                 docs1.push(serde_json::json!(
@@ -1795,7 +1809,7 @@ pub(crate) mod tests {
 
         // Fourth Batch: replace the documents without soft-deletion
         {
-            index.index_documents_config.disable_soft_deletion = true;
+            index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysHard;
             let mut docs1 = vec![];
             for i in 0..3 {
                 docs1.push(serde_json::json!(
@@ -1867,6 +1881,7 @@ pub(crate) mod tests {
     fn bug_3021_first() {
         // https://github.com/meilisearch/meilisearch/issues/3021
         let mut index = TempIndex::new();
+        index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysSoft;
         index.index_documents_config.update_method = IndexDocumentsMethod::ReplaceDocuments;
 
         index
@@ -1891,11 +1906,7 @@ pub(crate) mod tests {
         "###);
         db_snap!(index, soft_deleted_documents_ids, 1, @"[]");
 
-        let mut wtxn = index.write_txn().unwrap();
-        let mut delete = DeleteDocuments::new(&mut wtxn, &index).unwrap();
-        delete.delete_external_id("34");
-        delete.execute().unwrap();
-        wtxn.commit().unwrap();
+        index.delete_document("34");
 
         db_snap!(index, documents_ids, @"[0, ]");
         db_snap!(index, external_documents_ids, 2, @r###"
@@ -1936,11 +1947,7 @@ pub(crate) mod tests {
         db_snap!(index, soft_deleted_documents_ids, 4, @"[]");
 
         // We do the test again, but deleting the document with id 0 instead of id 1 now
-        let mut wtxn = index.write_txn().unwrap();
-        let mut delete = DeleteDocuments::new(&mut wtxn, &index).unwrap();
-        delete.delete_external_id("38");
-        delete.execute().unwrap();
-        wtxn.commit().unwrap();
+        index.delete_document("38");
 
         db_snap!(index, documents_ids, @"[1, ]");
         db_snap!(index, external_documents_ids, 5, @r###"
@@ -1987,6 +1994,7 @@ pub(crate) mod tests {
     fn bug_3021_second() {
         // https://github.com/meilisearch/meilisearch/issues/3021
         let mut index = TempIndex::new();
+        index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysSoft;
         index.index_documents_config.update_method = IndexDocumentsMethod::UpdateDocuments;
 
         index
@@ -2011,11 +2019,7 @@ pub(crate) mod tests {
         "###);
         db_snap!(index, soft_deleted_documents_ids, 1, @"[]");
 
-        let mut wtxn = index.write_txn().unwrap();
-        let mut delete = DeleteDocuments::new(&mut wtxn, &index).unwrap();
-        delete.delete_external_id("34");
-        delete.execute().unwrap();
-        wtxn.commit().unwrap();
+        index.delete_document("34");
 
         db_snap!(index, documents_ids, @"[0, ]");
         db_snap!(index, external_documents_ids, 2, @r###"
@@ -2116,6 +2120,7 @@ pub(crate) mod tests {
     fn bug_3021_third() {
         // https://github.com/meilisearch/meilisearch/issues/3021
         let mut index = TempIndex::new();
+        index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysSoft;
         index.index_documents_config.update_method = IndexDocumentsMethod::UpdateDocuments;
 
         index
@@ -2142,11 +2147,7 @@ pub(crate) mod tests {
         "###);
         db_snap!(index, soft_deleted_documents_ids, 1, @"[]");
 
-        let mut wtxn = index.write_txn().unwrap();
-        let mut delete = DeleteDocuments::new(&mut wtxn, &index).unwrap();
-        delete.delete_external_id("3");
-        delete.execute().unwrap();
-        wtxn.commit().unwrap();
+        index.delete_document("3");
 
         db_snap!(index, documents_ids, @"[1, 2, ]");
         db_snap!(index, external_documents_ids, 2, @r###"
@@ -2158,7 +2159,7 @@ pub(crate) mod tests {
         "###);
         db_snap!(index, soft_deleted_documents_ids, 2, @"[0, ]");
 
-        index.index_documents_config.disable_soft_deletion = true;
+        index.index_documents_config.deletion_strategy = DeletionStrategy::AlwaysHard;
 
         index.add_documents(documents!([{ "primary_key": "4", "a": 2 }])).unwrap();