Auto merge of #606 - Mark-Simulacrum:opt, r=Mark-Simulacrum

Increase cache size for sqlite

Mostly an experiment to see if this is an improvement in production.

Author: bors

src/db/mod.rs

@@ -19,6 +19,12 @@ struct ConnectionCustomizer;
 impl CustomizeConnection<Connection, ::rusqlite::Error> for ConnectionCustomizer {
     fn on_acquire(&self, conn: &mut Connection) -> Result<(), ::rusqlite::Error> {
         conn.execute("PRAGMA foreign_keys = ON;", [])?;
+        // Increase cache size from ~2 MB (current default) to ~100 MB.
+        //
+        // This should help sqlite keep pages in memory rather than needing to
+        // seek and read. Those typically hit the OS cache, but syscalls are
+        // still somewhat expensive at these volumes.
+        conn.execute("PRAGMA cache_size = -100000;", [])?;
         Ok(())
     }
 }