Add use_bfs_executor option (.new & :compile)

Author: Totktonada

graphql/impl.lua

@@ -56,8 +56,23 @@ local function gql_execute(qstate, variables, operation_name)
         assert(operation_type == 'query' or operation_type == 'mutation',
             'only "query" and "mutation" operation types are supported')
         local accessor = state.accessor
-
-        if operation_type == 'query' and accessor.name == 'shard' then
+        local cfg_use_bfs_executor = qstate.query_settings.use_bfs_executor or
+            state.use_bfs_executor
+
+        local use_bfs_executor = operation_type == 'query'
+        if use_bfs_executor then
+            if cfg_use_bfs_executor == 'never' then
+                use_bfs_executor = false
+            elseif cfg_use_bfs_executor == 'shard' then
+                use_bfs_executor = accessor.name == 'shard'
+            elseif cfg_use_bfs_executor == 'always' then
+                use_bfs_executor = true
+            else
+                error('Unknown use_bfs_executor: ' ..
+                    tostring(state.use_bfs_executor))
+            end
+        end
+        if use_bfs_executor then
             return bfs_executor.execute(state.schema, qstate.ast, variables,
                 operation_name, {
                     qcontext = qcontext,
@@ -117,6 +132,7 @@ end
 --- * resulting_object_cnt_max
 --- * fetched_object_cnt_max
 --- * timeout_ms
+--- * use_bfs_executor
 ---
 --- @treturn table compiled query with `execute` and `avro_schema` functions
 local function gql_compile(state, query, opts)
@@ -138,6 +154,7 @@ local function gql_compile(state, query, opts)
             resulting_object_cnt_max = opts.resulting_object_cnt_max,
             fetched_object_cnt_max = opts.fetched_object_cnt_max,
             timeout_ms = opts.timeout_ms,
+            use_bfs_executor = opts.use_bfs_executor,
         }
     }
 
@@ -291,6 +308,7 @@ end
 ---     timeout_ms = <number>,
 ---     enable_mutations = <boolean>,
 ---     disable_dangling_check = <boolean>,
+---     use_bfs_executor = 'never' | 'shard' (default) | 'always'
 --- })
 function impl.new(cfg)
     local cfg = cfg or {}
@@ -320,8 +338,17 @@ function impl.new(cfg)
         cfg.indexes = cfg.accessor.indexes
     end
 
+    check(cfg.disable_dangling_check, 'disable_dangling_check', 'boolean',
+        'nil')
+    check(cfg.use_bfs_executor, 'use_bfs_executor', 'string', 'nil')
+    assert(cfg.use_bfs_executor == 'never' or cfg.use_bfs_executor == 'shard'
+        or cfg.use_bfs_executor == 'always' or cfg.use_bfs_executor == nil,
+        "use_bfs_executor must be 'never', 'shard' (default) or 'always', '" ..
+        "got " .. tostring(cfg.use_bfs_executor))
+
     local state = {
         disable_dangling_check = cfg.disable_dangling_check,
+        use_bfs_executor = cfg.use_bfs_executor or 'shard',
     }
     convert_schema.convert(state, cfg)
     return setmetatable(state, {