Merge #3788

3788: Use `RoaringBitmap::deserialize_unchecked_from` to reduce the deserialization time r=irevoire a=Kerollmops

This pull request replaces the `RoaringBitmap::deserialize_from` methods with the `deserialize_unchecked_from` to avoid doing too much checks. We know the written bitmaps are valid as we do not disable the checks during the indexation phase.

I did a small test with #3780 and discovered that the deserialization time changed from 32% to 9.46% when using these changes. It seems it was low-hanging fruit hidden behind a leaf.

Co-authored-by: Kerollmops <clement@meilisearch.com>

milli/src/heed_codec/roaring_bitmap/cbo_roaring_bitmap_codec.rs

@@ -49,7 +49,7 @@ impl CboRoaringBitmapCodec {
         } else {
             // Otherwise, it means we used the classic RoaringBitmapCodec and
             // that the header takes threshold integers.
-            RoaringBitmap::deserialize_from(bytes)
+            RoaringBitmap::deserialize_unchecked_from(bytes)
         }
     }
 
@@ -69,7 +69,7 @@ impl CboRoaringBitmapCodec {
                     vec.push(integer);
                 }
             } else {
-                roaring |= RoaringBitmap::deserialize_from(bytes.as_ref())?;
+                roaring |= RoaringBitmap::deserialize_unchecked_from(bytes.as_ref())?;
             }
         }
 

milli/src/heed_codec/roaring_bitmap/roaring_bitmap_codec.rs

@@ -8,7 +8,7 @@ impl heed::BytesDecode<'_> for RoaringBitmapCodec {
     type DItem = RoaringBitmap;
 
     fn bytes_decode(bytes: &[u8]) -> Option<Self::DItem> {
-        RoaringBitmap::deserialize_from(bytes).ok()
+        RoaringBitmap::deserialize_unchecked_from(bytes).ok()
     }
 }