Fix external keydef compatibility with builtin merger (#175)

Co-authored-by: Oleg Babin <babinoleg@mail.ru>

Author: dokshina

.github/workflows/test_on_push.yaml

@@ -12,6 +12,10 @@ jobs:
     strategy:
       matrix:
         tarantool-version: ["1.10", "2.2", "2.3", "2.4", "2.5", "2.6", "2.7"]
+        remove-merger: [false]
+        include:
+          - tarantool-version: "2.7"
+            remove-merger: true
       fail-fast: false
     runs-on: [ubuntu-latest]
     steps:
@@ -24,6 +28,10 @@ jobs:
           tarantool --version
           ./deps.sh
 
+      - name: Remove external merger if needed
+        if: ${{ matrix.remove-merger }}
+        run: rm .rocks/lib/tarantool/tuple/merger.so
+
       # This server starts and listen on 8084 port that is used for tests
       - name: Stop Mono server
         run: sudo kill -9 $(sudo lsof -t -i tcp:8084) || true

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 * Compatibility with Tarantool versions that don't support key_def and merger modules.
 * Ignoring `opts.first` on `crud.pairs` call
+* External `keydef` compatibility with built-in `merger`
 
 ## [0.7.0] - 2021-05-27
 

crud/select/merger.lua

@@ -165,6 +165,10 @@ local function new(replicasets, space, index_id, func_name, func_args, opts)
     end
 
     local keydef = Keydef.new(space, opts.field_names, index_id)
+    -- When built-in merger is used with external keydef, `merger_lib.new(keydef)`
+    -- fails. It's simply fixed by casting `keydef` to 'struct key_def&'.
+    keydef = ffi.cast('struct key_def&', keydef)
+
     local merger = merger_lib.new(keydef, merger_sources, {
         reverse = reverse_tarantool_iters[opts.tarantool_iter],
     })