prim_import(): prefetch substitute info in parallel using queryMissing()

2012-07-09 09:59:34 -04:00 · 2012-07-09 09:59:34 -04:00 · 98a423b75a
parent 425cc612ad
commit 98a423b75a
1 changed files with 6 additions and 0 deletions
--- 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));