diff --git a/src/vault.rs b/src/vault.rs
index c4667fe..96de220 100644
--- a/src/vault.rs
+++ b/src/vault.rs
@@ -1,5 +1,6 @@
 mod euph;
 mod migrate;
+mod prepare;
 
 use std::path::Path;
 use std::{fs, thread};
@@ -70,6 +71,7 @@ pub fn launch(path: &Path) -> rusqlite::Result<Vault> {
     conn.pragma_update(None, "trusted_schema", false)?;
 
     migrate::migrate(&mut conn)?;
+    prepare::prepare(&mut conn)?;
 
     let (tx, rx) = mpsc::unbounded_channel();
     thread::spawn(move || run(conn, rx));
diff --git a/src/vault/migrate.rs b/src/vault/migrate.rs
index 1c019bb..3351eaa 100644
--- a/src/vault/migrate.rs
+++ b/src/vault/migrate.rs
@@ -60,13 +60,6 @@ fn m1(tx: &mut Transaction) -> rusqlite::Result<()> {
             CHECK (start IS NULL OR end IS NOT NULL)
         ) STRICT;
 
-        CREATE TABLE euph_trees (
-            room TEXT NOT NULL,
-            id INT NOT NULL,
-
-            PRIMARY KEY (room, id)
-        );
-
         CREATE INDEX euph_idx_msgs_room_id_parent
         ON euph_msgs (room, id, parent);
 
diff --git a/src/vault/prepare.rs b/src/vault/prepare.rs
new file mode 100644
index 0000000..c6f1ca1
--- /dev/null
+++ b/src/vault/prepare.rs
@@ -0,0 +1,29 @@
+use rusqlite::Connection;
+
+pub fn prepare(conn: &mut Connection) -> rusqlite::Result<()> {
+    conn.execute_batch(
+        "
+        CREATE TEMPORARY TABLE euph_trees (
+            room TEXT NOT NULL,
+            id INT NOT NULL,
+
+            PRIMARY KEY (room, id)
+        ) STRICT;
+
+        INSERT INTO euph_trees (room, id)
+        SELECT room, id
+        FROM euph_msgs
+        WHERE parent IS NULL
+        UNION
+        SELECT room, parent
+        FROM euph_msgs
+        WHERE parent IS NOT NULL
+        AND NOT EXISTS(
+            SELECT *
+            FROM euph_msgs AS parents
+            WHERE parents.room = euph_msgs.room
+            AND parents.id = euph_msgs.parent
+        );
+        ",
+    )
+}