From 0ade558999d6d13fb58f35853f201791e0b9339a Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@scylladb.com>
Date: Tue, 3 Apr 2018 12:22:14 +0300
Subject: [PATCH 1/2] api: simplify 6-argument map_reduce_cf() variant

The 6-argument map_reduce_cf function is identical to the 5-argument
version, except that it applies performs an extra cast (by calling
the 6th argument's operator=()).

Simplify the code by calling the 5-argument version from the 6-argument
version.

Reduces binary size by ~10%.
---
 api/column_family.hh | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/api/column_family.hh b/api/column_family.hh
index 3764b76db7..e29c5c22a6 100644
--- a/api/column_family.hh
+++ b/api/column_family.hh
@@ -58,20 +58,10 @@ future<json::json_return_type> map_reduce_cf(http_context& ctx, const sstring& n
     });
 }
 
-template<class Mapper, class I, class Reducer, class Result>
-future<I> map_reduce_cf_raw(http_context& ctx, const sstring& name, I init,
-        Mapper mapper, Reducer reducer, Result result) {
-    auto uuid = get_uuid(name, ctx.db.local());
-    return ctx.db.map_reduce0([mapper, uuid](database& db) {
-        return mapper(db.find_column_family(uuid));
-    }, init, reducer);
-}
-
-
 template<class Mapper, class I, class Reducer, class Result>
 future<json::json_return_type> map_reduce_cf(http_context& ctx, const sstring& name, I init,
         Mapper mapper, Reducer reducer, Result result) {
-    return map_reduce_cf_raw(ctx, name, init, mapper, reducer, result).then([result](const I& res) mutable {
+    return map_reduce_cf_raw(ctx, name, init, mapper, reducer).then([result](const I& res) mutable {
         result = res;
         return make_ready_future<json::json_return_type>(result);
     });

From 6c35db2c4441831ce53037803b78f5ace778b2f5 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@scylladb.com>
Date: Tue, 3 Apr 2018 13:08:22 +0300
Subject: [PATCH 2/2] api: type-erase all-column_family map_reduce variant

Encapsulate the map_reduce parameters in type-erased
std::function, as well as the iterator-on-all-column-families
logic. Reduces binary size by 18%.
---
 api/column_family.hh | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/api/column_family.hh b/api/column_family.hh
index e29c5c22a6..0d3879fcca 100644
--- a/api/column_family.hh
+++ b/api/column_family.hh
@@ -67,16 +67,33 @@ future<json::json_return_type> map_reduce_cf(http_context& ctx, const sstring& n
     });
 }
 
-template<class Mapper, class I, class Reducer>
-future<I> map_reduce_cf_raw(http_context& ctx, I init,
-        Mapper mapper, Reducer reducer) {
-    return ctx.db.map_reduce0([mapper, init, reducer](database& db) {
+struct map_reduce_column_families_locally {
+    std::any init;
+    std::function<std::any (column_family&)> mapper;
+    std::function<std::any (std::any, std::any)> reducer;
+    std::any operator()(database& db) const {
         auto res = init;
         for (auto i : db.get_column_families()) {
             res = reducer(res, mapper(*i.second.get()));
         }
         return res;
-    }, init, reducer);
+    }
+};
+
+template<class Mapper, class I, class Reducer>
+future<I> map_reduce_cf_raw(http_context& ctx, I init,
+        Mapper mapper, Reducer reducer) {
+    using mapper_type = std::function<std::any (column_family&)>;
+    using reducer_type = std::function<std::any (std::any, std::any)>;
+    auto wrapped_mapper = mapper_type([mapper = std::move(mapper)] (column_family& cf) mutable {
+        return I(mapper(cf));
+    });
+    auto wrapped_reducer = reducer_type([reducer = std::move(reducer)] (std::any a, std::any b) mutable {
+        return I(reducer(std::any_cast<I>(std::move(a)), std::any_cast<I>(std::move(b))));
+    });
+    return ctx.db.map_reduce0(map_reduce_column_families_locally{init, std::move(wrapped_mapper), wrapped_reducer}, std::any(init), wrapped_reducer).then([] (std::any res) {
+        return std::any_cast<I>(std::move(res));
+    });
 }