[PATCH v2 2/3] schema: inherit vinyl/memtx_index_mt from base index mt

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Now space.bless() in Lua serves to choose a correct index
metatable that depends on a space engine. Vinyl index methods
must not use FFI since yield breaks it. Lets do not choose
correct methods one by one in space.bless, create them only
once on start, and then just do copy of needed table.
---
 src/box/lua/schema.lua | 109 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 66 insertions(+), 43 deletions(-)

diff --git a/src/box/lua/schema.lua b/src/box/lua/schema.lua
index 8b6f69ad8..4b5eeeda9 100644
--- a/src/box/lua/schema.lua
+++ b/src/box/lua/schema.lua
@@ -1074,9 +1074,32 @@ end
 
 internal.check_iterator_type = check_iterator_type -- export for net.box
 
-local index_mt = {}
+local function forbid_new_index(t, k, v)
+    return error('Attempt to modify a read-only table')
+end
+
+local base_index_mt = {}
+base_index_mt.__index = base_index_mt
+--
+-- Inherit engine specific index metatables from a base one.
+--
+local vinyl_index_mt = {}
+vinyl_index_mt.__index = vinyl_index_mt
+local memtx_index_mt = {}
+memtx_index_mt.__index = memtx_index_mt
+--
+-- When a new method is added below to base index mt, the same
+-- method is added both to vinyl and memtx index mt.
+--
+setmetatable(base_index_mt, {
+    __newindex = function(t, k, v)
+        vinyl_index_mt[k] = v
+        memtx_index_mt[k] = v
+        rawset(t, k, v)
+    end
+})
 -- __len and __index
-index_mt.len = function(index)
+base_index_mt.len = function(index)
     check_index_arg(index, 'len')
     local ret = builtin.box_index_len(index.space_id, index.id)
     if ret == -1 then
@@ -1085,7 +1108,7 @@ index_mt.len = function(index)
     return tonumber(ret)
 end
 -- index.bsize
-index_mt.bsize = function(index)
+base_index_mt.bsize = function(index)
     check_index_arg(index, 'bsize')
     local ret = builtin.box_index_bsize(index.space_id, index.id)
     if ret == -1 then
@@ -1093,13 +1116,11 @@ index_mt.bsize = function(index)
     end
     return tonumber(ret)
 end
-index_mt.__len = index_mt.len -- Lua 5.2 compatibility
-index_mt.__newindex = function(table, index)
-    return error('Attempt to modify a read-only table')
-end
-index_mt.__index = index_mt
+-- Lua 5.2 compatibility
+base_index_mt.__len = base_index_mt.len
+base_index_mt.__newindex = forbid_new_index
 -- min and max
-index_mt.min_ffi = function(index, key)
+base_index_mt.min_ffi = function(index, key)
     check_index_arg(index, 'min')
     local pkey, pkey_end = tuple_encode(key)
     if builtin.box_index_min(index.space_id, index.id,
@@ -1111,12 +1132,12 @@ index_mt.min_ffi = function(index, key)
         return
     end
 end
-index_mt.min_luac = function(index, key)
+base_index_mt.min_luac = function(index, key)
     check_index_arg(index, 'min')
     key = keify(key)
     return internal.min(index.space_id, index.id, key);
 end
-index_mt.max_ffi = function(index, key)
+base_index_mt.max_ffi = function(index, key)
     check_index_arg(index, 'max')
     local pkey, pkey_end = tuple_encode(key)
     if builtin.box_index_max(index.space_id, index.id,
@@ -1128,12 +1149,12 @@ index_mt.max_ffi = function(index, key)
         return
     end
 end
-index_mt.max_luac = function(index, key)
+base_index_mt.max_luac = function(index, key)
     check_index_arg(index, 'max')
     key = keify(key)
     return internal.max(index.space_id, index.id, key);
 end
-index_mt.random_ffi = function(index, rnd)
+base_index_mt.random_ffi = function(index, rnd)
     check_index_arg(index, 'random')
     rnd = rnd or math.random()
     if builtin.box_index_random(index.space_id, index.id, rnd,
@@ -1145,13 +1166,13 @@ index_mt.random_ffi = function(index, rnd)
         return
     end
 end
-index_mt.random_luac = function(index, rnd)
+base_index_mt.random_luac = function(index, rnd)
     check_index_arg(index, 'random')
     rnd = rnd or math.random()
     return internal.random(index.space_id, index.id, rnd);
 end
 -- iteration
-index_mt.pairs_ffi = function(index, key, opts)
+base_index_mt.pairs_ffi = function(index, key, opts)
     check_index_arg(index, 'pairs')
     local pkey, pkey_end = tuple_encode(key)
     local itype = check_iterator_type(opts, pkey + 1 >= pkey_end);
@@ -1166,7 +1187,7 @@ index_mt.pairs_ffi = function(index, key, opts)
     return fun.wrap(iterator_gen, keybuf,
         ffi.gc(cdata, builtin.box_iterator_free))
 end
-index_mt.pairs_luac = function(index, key, opts)
+base_index_mt.pairs_luac = function(index, key, opts)
     check_index_arg(index, 'pairs')
     key = keify(key)
     local itype = check_iterator_type(opts, #key == 0);
@@ -1178,7 +1199,7 @@ index_mt.pairs_luac = function(index, key, opts)
 end
 
 -- index subtree size
-index_mt.count_ffi = function(index, key, opts)
+base_index_mt.count_ffi = function(index, key, opts)
     check_index_arg(index, 'count')
     local pkey, pkey_end = tuple_encode(key)
     local itype = check_iterator_type(opts, pkey + 1 >= pkey_end);
@@ -1189,14 +1210,14 @@ index_mt.count_ffi = function(index, key, opts)
     end
     return tonumber(count)
 end
-index_mt.count_luac = function(index, key, opts)
+base_index_mt.count_luac = function(index, key, opts)
     check_index_arg(index, 'count')
     key = keify(key)
     local itype = check_iterator_type(opts, #key == 0);
     return internal.count(index.space_id, index.id, itype, key);
 end
 
-index_mt.get_ffi = function(index, key)
+base_index_mt.get_ffi = function(index, key)
     check_index_arg(index, 'get')
     local key, key_end = tuple_encode(key)
     if builtin.box_index_get(index.space_id, index.id,
@@ -1208,7 +1229,7 @@ index_mt.get_ffi = function(index, key)
         return
     end
 end
-index_mt.get_luac = function(index, key)
+base_index_mt.get_luac = function(index, key)
     check_index_arg(index, 'get')
     key = keify(key)
     return internal.get(index.space_id, index.id, key)
@@ -1229,7 +1250,7 @@ local function check_select_opts(opts, key_is_nil)
     return iterator, offset, limit
 end
 
-index_mt.select_ffi = function(index, key, opts)
+base_index_mt.select_ffi = function(index, key, opts)
     check_index_arg(index, 'select')
     local key, key_end = tuple_encode(key)
     local iterator, offset, limit = check_select_opts(opts, key + 1 >= key_end)
@@ -1251,7 +1272,7 @@ index_mt.select_ffi = function(index, key, opts)
     return ret
 end
 
-index_mt.select_luac = function(index, key, opts)
+base_index_mt.select_luac = function(index, key, opts)
     check_index_arg(index, 'select')
     local key = keify(key)
     local iterator, offset, limit = check_select_opts(opts, #key == 0)
@@ -1259,28 +1280,28 @@ index_mt.select_luac = function(index, key, opts)
         offset, limit, key)
 end
 
-index_mt.update = function(index, key, ops)
+base_index_mt.update = function(index, key, ops)
     check_index_arg(index, 'update')
     return internal.update(index.space_id, index.id, keify(key), ops);
 end
-index_mt.delete = function(index, key)
+base_index_mt.delete = function(index, key)
     check_index_arg(index, 'delete')
     return internal.delete(index.space_id, index.id, keify(key));
 end
 
-index_mt.info = function(index)
+base_index_mt.info = function(index)
     return internal.info(index.space_id, index.id);
 end
 
-index_mt.drop = function(index)
+base_index_mt.drop = function(index)
     check_index_arg(index, 'drop')
     return box.schema.index.drop(index.space_id, index.id)
 end
-index_mt.rename = function(index, name)
+base_index_mt.rename = function(index, name)
     check_index_arg(index, 'rename')
     return box.schema.index.rename(index.space_id, index.id, name)
 end
-index_mt.alter = function(index, options)
+base_index_mt.alter = function(index, options)
     check_index_arg(index, 'alter')
     if index.id == nil or index.space_id == nil then
         box.error(box.error.PROC_LUA, "Usage: index:alter{opts}")
@@ -1288,6 +1309,17 @@ index_mt.alter = function(index, options)
     return box.schema.index.alter(index.space_id, index.id, options)
 end
 
+local read_ops = {'select', 'get', 'min', 'max', 'count', 'random', 'pairs'}
+for _, op in ipairs(read_ops) do
+    vinyl_index_mt[op] = base_index_mt[op..'_luac']
+    memtx_index_mt[op] = base_index_mt[op..'_ffi']
+end
+-- Lua 5.2 compatibility
+vinyl_index_mt.__pairs = vinyl_index_mt.pairs
+vinyl_index_mt.__ipairs = vinyl_index_mt.pairs
+memtx_index_mt.__pairs = memtx_index_mt.pairs
+memtx_index_mt.__ipairs = memtx_index_mt.pairs
+
 local space_mt = {}
 space_mt.len = function(space)
     check_space_arg(space, 'len')
@@ -1313,7 +1345,7 @@ space_mt.bsize = function(space)
     end
     return builtin.space_bsize(s)
 end
-space_mt.__newindex = index_mt.__newindex
+space_mt.__newindex = forbid_new_index
 
 space_mt.get = function(space, key)
     check_space_arg(space, 'get')
@@ -1409,22 +1441,13 @@ end
 space_mt.__index = space_mt
 
 function box.schema.space.bless(space)
-    local index_mt = table.deepcopy(index_mt)
     local space_mt = table.deepcopy(space_mt)
-    -- true if reading operations may yield
-    local read_yields = space.engine == 'vinyl'
-    local read_ops = {'select', 'get', 'min', 'max', 'count', 'random', 'pairs'}
-    for _, op in ipairs(read_ops) do
-        if read_yields then
-            -- use Lua/C implmenetation
-            index_mt[op] = index_mt[op .. "_luac"]
-        else
-            -- use FFI implementation
-            index_mt[op] = index_mt[op .. "_ffi"]
-        end
+    local index_mt
+    if space.engine == 'vinyl' then
+        index_mt = table.deepcopy(vinyl_index_mt)
+    else
+        index_mt = table.deepcopy(memtx_index_mt)
     end
-    index_mt.__pairs = index_mt.pairs -- Lua 5.2 compatibility
-    index_mt.__ipairs = index_mt.pairs -- Lua 5.2 compatibility
 
     setmetatable(space, space_mt)
     if type(space.index) == 'table' and space.enabled then
-- 
2.14.3 (Apple Git-98)