Fully implemented result handling with removing query when it's done

Author: dankmolot

source/query.cpp

@@ -39,6 +39,32 @@ void query_failed(GLua::ILuaInterface* lua, Connection* state) {
     }
 }
 
+inline bool bad_result(PGresult* result) {
+    if (!result) {
+        return true;
+    }
+
+    auto status = PQresultStatus(result);
+
+    return status == PGRES_BAD_RESPONSE || status == PGRES_NONFATAL_ERROR ||
+           status == PGRES_FATAL_ERROR;
+}
+
+void query_result(GLua::ILuaInterface* lua, pg::result&& result,
+                  GLua::AutoReference& callback) {
+    if (callback.Push()) {
+        if (!bad_result(result.get())) {
+            lua->PushBool(true);
+            create_result_table(lua, result.get());
+        } else {
+            lua->PushBool(false);
+            lua->PushString(PQresultErrorMessage(result.get()));
+        }
+
+        pcall(lua, 2, 0);
+    }
+}
+
 // returns true if poll was successful
 // returns false if there was an error
 inline bool poll_query(PGconn* conn, Query& query) {
@@ -55,15 +81,39 @@ inline bool poll_query(PGconn* conn, Query& query) {
     return true;
 }
 
-bool bad_result(PGresult* result) {
+void process_result(GLua::ILuaInterface* lua, Connection* state,
+                    pg::result&& result) {
+    // query is done
     if (!result) {
-        return true;
+        state->query.reset();
+        return process_query(lua, state);
     }
 
-    auto status = PQresultStatus(result);
+    // next result might be empty,
+    // that means that query is done
+    // and we need to remove query from the state
+    // so callback can add another query
+    if (!pg::isBusy(state->conn)) {
+        auto next_result = pg::getResult(state->conn);
+        if (!next_result) {
+            // query is done, we need to remove query from the state
+            Query query = std::move(*state->query);
+            state->query.reset();
 
-    return status == PGRES_BAD_RESPONSE || status == PGRES_NONFATAL_ERROR ||
-           status == PGRES_FATAL_ERROR;
+            query_result(lua, std::move(result), query.callback);
+
+            // callback might added another query, process it rightaway
+            process_query(lua, state);
+        } else {
+            // query is not done, but also since we own next result
+            // we need to call query callback and process next result
+            query_result(lua, std::move(result), state->query->callback);
+            process_result(lua, state, std::move(next_result));
+        }
+    } else {
+        // query is not done, but we don't need to process next result
+        query_result(lua, std::move(result), state->query->callback);
+    }
 }
 
 void async_postgres::process_query(GLua::ILuaInterface* lua,
@@ -90,26 +140,8 @@ void async_postgres::process_query(GLua::ILuaInterface* lua,
         return process_query(lua, state);
     }
 
-    while (PQisBusy(state->conn.get()) == 0) {
-        auto result = pg::getResult(state->conn);
-        if (!result) {
-            // query is done
-            // TODO: remove query if we have a final result
-            state->query.reset();
-            return process_query(lua, state);
-        }
-
-        if (query.callback) {
-            query.callback.Push();
-            if (!bad_result(result.get())) {
-                lua->PushBool(true);
-                create_result_table(lua, result.get());
-            } else {
-                lua->PushBool(false);
-                lua->PushString(PQresultErrorMessage(result.get()));
-            }
-
-            pcall(lua, 2, 0);
-        }
+    // ensure that getting result won't block
+    if (!pg::isBusy(state->conn)) {
+        return process_result(lua, state, pg::getResult(state->conn));
     }
 }

source/safe_pg.hpp

@@ -23,4 +23,8 @@ namespace async_postgres::pg {
     inline notify getNotify(conn& conn) {
         return notify(PQnotifies(conn.get()), &PQfreemem);
     }
+
+    // misc
+
+    inline bool isBusy(conn& conn) { return PQisBusy(conn.get()) == 1; }
 }  // namespace async_postgres::pg