diff --git a/crates/ra_analysis/src/db.rs b/crates/ra_analysis/src/db.rs
index 3d0f13f341..94729d2967 100644
--- a/crates/ra_analysis/src/db.rs
+++ b/crates/ra_analysis/src/db.rs
@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::{fmt, sync::Arc};
 use salsa::{self, Database};
 use ra_db::{LocationIntener, BaseDatabase};
 use hir::{self, DefId, DefLoc};
@@ -13,11 +13,19 @@ pub(crate) struct RootDatabase {
     id_maps: Arc<IdMaps>,
 }
 
-#[derive(Debug, Default)]
+#[derive(Default)]
 struct IdMaps {
     defs: LocationIntener<DefLoc, DefId>,
 }
 
+impl fmt::Debug for IdMaps {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("IdMaps")
+            .field("n_defs", &self.defs.len())
+            .finish()
+    }
+}
+
 impl salsa::Database for RootDatabase {
     fn salsa_runtime(&self) -> &salsa::Runtime<RootDatabase> {
         &self.runtime
diff --git a/crates/ra_db/src/loc2id.rs b/crates/ra_db/src/loc2id.rs
index 69ba43d0f7..2dc7930d8e 100644
--- a/crates/ra_db/src/loc2id.rs
+++ b/crates/ra_db/src/loc2id.rs
@@ -42,6 +42,10 @@ where
     ID: NumericId,
     LOC: Clone + Eq + Hash,
 {
+    pub fn len(&self) -> usize {
+        self.loc2id.len()
+    }
+
     pub fn loc2id(&mut self, loc: &LOC) -> ID {
         match self.loc2id.get(loc) {
             Some(id) => return id.clone(),
@@ -91,6 +95,9 @@ where
     ID: NumericId,
     LOC: Clone + Eq + Hash,
 {
+    pub fn len(&self) -> usize {
+        self.map.lock().len()
+    }
     pub fn loc2id(&self, loc: &LOC) -> ID {
         self.map.lock().loc2id(loc)
     }