Call queryMissing() prior to building

Without this, substitute info is fetched sequentially, which is
superslow. In the old UI (e.g. nix-build), we call printMissing(),
which calls queryMissing(), thereby preheating the binary cache
cache. But the new UI doesn't do that.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 8fa84d3a2787..a82aa4e9cfa5 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -107,6 +107,8 @@ void Store::queryMissing(const PathSet & targets,
     PathSet & willBuild_, PathSet & willSubstitute_, PathSet & unknown_,
     unsigned long long & downloadSize_, unsigned long long & narSize_)
 {
+    Activity act(*logger, lvlDebug, actUnknown, "querying info about missing paths");
+
     downloadSize_ = narSize_ = 0;
 
     ThreadPool pool;