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authorEelco Dolstra <eelco.dolstra@logicblox.com>2012-07-09T13·59-0400
committerEelco Dolstra <eelco.dolstra@logicblox.com>2012-07-09T13·59-0400
commit98a423b75aa9061f0164c316f9d2481ce6d5e2f1 (patch)
treeeeff6cf0d5c13e6b93dc0947846e348177066650
parent425cc612ad4835d29bce081a67ad161d06063b51 (diff)
prim_import(): prefetch substitute info in parallel using queryMissing()
-rw-r--r--src/libexpr/primops.cc6
1 files changed, 6 insertions, 0 deletions
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 7587dccea4aa..354fc39be073 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -51,6 +51,12 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
                 % path % ctx);
         if (isDerivation(ctx))
             try {
+                /* For performance, prefetch all substitute info. */
+                PathSet willBuild, willSubstitute, unknown;
+                unsigned long long downloadSize, narSize;
+                queryMissing(*store, singleton<PathSet>(ctx),
+                    willBuild, willSubstitute, unknown, downloadSize, narSize);
+                  
                 /* !!! If using a substitute, we only need to fetch
                    the selected output of this derivation. */
                 store->buildPaths(singleton<PathSet>(ctx));