SERVER-48228 Move slot-based execution engine and supporting changes into the master branch

This is an initial commit for the slot-based execution engine (SBE) which contains:
   * Implementation of the core slot-based engine.
   * The SBE stage builder, which is responsible for translating a QuerySolution tree
     into an SBE plan.
   * Other changes necessary for integration with the find command.

Co-authored-by: Anton Korshunov <anton.korshunov@mongodb.com>
Co-authored-by: Justin Seyster <justin.seyster@mongodb.com>
Co-authored-by: David Storch <david.storch@mongodb.com>

1 files changed, 61 insertions, 0 deletions

diff --git a/src/mongo/db/query/plan_yield_policy_sbe.cpp b/src/mongo/db/query/plan_yield_policy_sbe.cpp
new file mode 100644
index 00000000000..c7a76154f3c
--- /dev/null
+++ b/src/mongo/db/query/plan_yield_policy_sbe.cpp
@@ -0,0 +1,61 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/query/plan_yield_policy_sbe.h"
+
+namespace mongo {
+
+// TODO SERVER-48616: Need to change how we bump the CurOp yield counter. We shouldn't do it here
+// so that SBE does not depend on CurOp. But we should still expose that statistic and keep it fresh
+// as the operation executes.
+Status PlanYieldPolicySBE::yield(OperationContext* opCtx, std::function<void()> whileYieldingFn) {
+    if (!_rootStage) {
+        // This yield policy isn't bound to an execution tree yet.
+        return Status::OK();
+    }
+
+    try {
+        _rootStage->saveState();
+
+        opCtx->recoveryUnit()->abandonSnapshot();
+
+        if (whileYieldingFn) {
+            whileYieldingFn();
+        }
+
+        _rootStage->restoreState();
+    } catch (...) {
+        return exceptionToStatus();
+    }
+
+    return Status::OK();
+}
+}  // namespace mongo