From edf9eb8181e01f6b2123e5690019cfeeb44fc1c2 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Fri, 7 Oct 2016 19:57:47 +0200
Subject: [PATCH] querySubstitutablePaths(): Don't query paths for which we
 already have a substituter

---
 src/libstore/local-store.cc | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 41e1c37a0..4f2c433b8 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -781,14 +781,27 @@ Path LocalStore::queryPathFromHashPart(const string & hashPart)
 PathSet LocalStore::querySubstitutablePaths(const PathSet & paths)
 {
     if (!settings.useSubstitutes) return PathSet();
+
+    auto remaining = paths;
     PathSet res;
+
     for (auto & sub : getDefaultSubstituters()) {
-        if (res.size() == paths.size()) break;
+        if (remaining.empty()) break;
         if (sub->storeDir != storeDir) continue;
         if (!sub->wantMassQuery()) continue;
-        for (auto path : sub->queryValidPaths(paths))
-            res.insert(path);
+
+        auto valid = sub->queryValidPaths(remaining);
+
+        PathSet remaining2;
+        for (auto & path : remaining)
+            if (valid.count(path))
+                res.insert(path);
+            else
+                remaining2.insert(path);
+
+        std::swap(remaining, remaining2);
     }
+
     return res;
 }