mononoke/segmented_changelog: fix leader fallbacks being the wrong way around

Summary:
We have fallback logic to go to the leader if the data we want is missing in
the replica, but right now it's backwards so we go to the leader to find data
we actually *did* find in the replica (and we don't go to the leader for
missing data).

Reviewed By: sfilipco

Differential Revision: D26103898

fbshipit-source-id: 535abab2a3093165f1d55359d102a7a7cb542a9c

eden/mononoke/segmented_changelog/src/idmap/sql.rs

@@ -294,7 +294,7 @@ impl IdMap for SqlIdMap {
         let mut cs_ids = select_vertexes(&self.connections.read_connection, &to_query).await?;
         let not_found_in_replica: Vec<_> = vertexes
             .iter()
-            .filter(|x| cs_ids.contains_key(x))
+            .filter(|x| !cs_ids.contains_key(x))
             .map(|v| v.0)
             .collect();
         if !not_found_in_replica.is_empty() {
@@ -355,6 +355,7 @@ mod tests {
     use super::*;
 
     use maplit::hashmap;
+    use sql::{rusqlite::Connection as SqliteConnection, Connection};
 
     use fbinit::FacebookInit;
 
@@ -491,6 +492,41 @@ mod tests {
         Ok(())
     }
 
+    #[fbinit::compat_test]
+    async fn test_find_many_changeset_ids_leader_fallback(fb: FacebookInit) -> Result<()> {
+        fn conn() -> Result<Connection> {
+            let con = SqliteConnection::open_in_memory()?;
+            con.execute_batch(SegmentedChangelogBuilder::CREATION_QUERY)?;
+            Ok(Connection::with_sqlite(con))
+        }
+
+        let ctx = CoreContext::test_mock(fb);
+
+        let leader = conn()?;
+        let replica = conn()?;
+
+        let conns = SqlConnections {
+            write_connection: leader.clone(),
+            read_connection: replica,
+            read_master_connection: leader,
+        };
+
+        let idmap = SegmentedChangelogBuilder::new()
+            .with_sql_connections(conns)
+            .with_repo_id(RepositoryId::new(0))
+            .build_sql_idmap()?;
+
+        idmap.insert(&ctx, Vertex(0), ONES_CSID).await?;
+
+        let res = idmap.get_changeset_id(&ctx, Vertex(0)).await?;
+        assert_eq!(res, ONES_CSID);
+
+        let res = idmap.find_many_changeset_ids(&ctx, vec![Vertex(0)]).await?;
+        assert_eq!(res, hashmap![Vertex(0) => ONES_CSID]);
+
+        Ok(())
+    }
+
     #[fbinit::compat_test]
     async fn test_many_repo_id_many_versions(fb: FacebookInit) -> Result<()> {
         let ctx = CoreContext::test_mock(fb);