From 9a266a531b39e7ba2623b1dff0b3e6caf2ac7e62 Mon Sep 17 00:00:00 2001
From: mpostma <postma.marin@protonmail.com>
Date: Tue, 12 Oct 2021 10:59:14 +0200
Subject: [PATCH 1/2] test correct primary key inference

---
 milli/src/update/index_documents/transform.rs | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/milli/src/update/index_documents/transform.rs b/milli/src/update/index_documents/transform.rs
index 8d656e50c..f4cbc8e22 100644
--- a/milli/src/update/index_documents/transform.rs
+++ b/milli/src/update/index_documents/transform.rs
@@ -497,6 +497,7 @@ mod test {
     use super::*;
 
     mod compute_primary_key {
+
         use super::{compute_primary_key_pair, FieldsIdsMap};
 
         #[test]
@@ -537,5 +538,27 @@ mod test {
             assert!(result.is_err());
             assert_eq!(fields_map.len(), 0);
         }
+
+    }
+
+    mod primary_key_inference {
+        use bimap::BiHashMap;
+
+        use crate::update::index_documents::transform::find_primary_key;
+
+        #[test]
+        fn primary_key_infered_on_first_field() {
+            // We run the test multiple times to change the order in which the fields are iterated upon.
+            for _ in 1..50 {
+                let mut map = BiHashMap::new();
+                map.insert(1, "fakeId".to_string());
+                map.insert(2, "fakeId".to_string());
+                map.insert(3, "fakeId".to_string());
+                map.insert(4, "fakeId".to_string());
+                map.insert(0, "realId".to_string());
+
+                assert_eq!(find_primary_key(&map), Some("realId"));
+            }
+        }
     }
 }

From 86ead92ed5155db84a4ea401a09e025eec9715d2 Mon Sep 17 00:00:00 2001
From: mpostma <postma.marin@protonmail.com>
Date: Tue, 12 Oct 2021 11:14:12 +0200
Subject: [PATCH 2/2] infer primary key on sorted fields

---
 milli/src/update/index_documents/transform.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/milli/src/update/index_documents/transform.rs b/milli/src/update/index_documents/transform.rs
index f4cbc8e22..c0c88abed 100644
--- a/milli/src/update/index_documents/transform.rs
+++ b/milli/src/update/index_documents/transform.rs
@@ -77,7 +77,9 @@ fn create_fields_mapping(
 
 fn find_primary_key(index: &bimap::BiHashMap<u16, String>) -> Option<&str> {
     index
-        .right_values()
+        .iter()
+        .sorted_by_key(|(k, _)| *k)
+        .map(|(_, v)| v)
         .find(|v| v.to_lowercase().contains(DEFAULT_PRIMARY_KEY_NAME))
         .map(String::as_str)
 }
@@ -497,7 +499,6 @@ mod test {
     use super::*;
 
     mod compute_primary_key {
-
         use super::{compute_primary_key_pair, FieldsIdsMap};
 
         #[test]
@@ -538,7 +539,6 @@ mod test {
             assert!(result.is_err());
             assert_eq!(fields_map.len(), 0);
         }
-
     }
 
     mod primary_key_inference {