Don't do full text search on empty strings

I was going through our log filters to see if they were all still
needed. We were specifically filtering out `text-search query doesn't
contain lexemes: ""`. This happens whenever someone runs `cargo search`
with no parameters, resulting in a request like `?q=&page=1`.

Rather than filtering this out of our logs, let's avoid doing full text
search at all. This will reduce load on our DB server. This does change
the behavior from returning nothing to returning the first 10 crates,
but that's probably what the user wanted anyway.

Author: sgrif

src/controllers/krate/search.rs

@@ -52,23 +52,25 @@ pub fn search(req: &mut Request) -> CargoResult<Response> {
         .into_boxed();
 
     if let Some(q_string) = params.get("q") {
-        let sort = params.get("sort").map(|s| &**s).unwrap_or("relevance");
-        let q = plainto_tsquery(q_string);
-        query = query.filter(
-            q.matches(crates::textsearchable_index_col)
-                .or(Crate::with_name(q_string)),
-        );
-
-        query = query.select((
-            ALL_COLUMNS,
-            Crate::with_name(q_string),
-            recent_crate_downloads::downloads.nullable(),
-        ));
-        query = query.order(Crate::with_name(q_string).desc());
-
-        if sort == "relevance" {
-            let rank = ts_rank_cd(crates::textsearchable_index_col, q);
-            query = query.then_order_by(rank.desc())
+        if !q_string.is_empty() {
+            let sort = params.get("sort").map(|s| &**s).unwrap_or("relevance");
+            let q = plainto_tsquery(q_string);
+            query = query.filter(
+                q.matches(crates::textsearchable_index_col)
+                    .or(Crate::with_name(q_string)),
+            );
+
+            query = query.select((
+                ALL_COLUMNS,
+                Crate::with_name(q_string),
+                recent_crate_downloads::downloads.nullable(),
+            ));
+            query = query.order(Crate::with_name(q_string).desc());
+
+            if sort == "relevance" {
+                let rank = ts_rank_cd(crates::textsearchable_index_col, q);
+                query = query.then_order_by(rank.desc())
+            }
         }
     }