From b9d2e18ca68246e5d21ed42a846ff4094867f159 Mon Sep 17 00:00:00 2001
From: Mathias Stearn <mathias@10gen.com>
Date: Mon, 6 Jul 2015 19:16:30 -0400
Subject: SERVER-17364 Don't stash RecoveryUnits across getMores

We now tell PlanExecutors to detach from their OperationContexts and to shed
all storage engine resources before stashing the ClientCursor. This is a
heavier weight operation than a normal save/restoreState which is no longer
allowed to change the OperationContext.
---
 src/mongo/db/clientcursor.h | 60 +++++++--------------------------------------
 1 file changed, 9 insertions(+), 51 deletions(-)

(limited to 'src/mongo/db/clientcursor.h')

diff --git a/src/mongo/db/clientcursor.h b/src/mongo/db/clientcursor.h
index 3f7e9797ae5..832d24e9a87 100644
--- a/src/mongo/db/clientcursor.h
+++ b/src/mongo/db/clientcursor.h
@@ -59,12 +59,15 @@ public:
     ClientCursor(CursorManager* cursorManager,
                  PlanExecutor* exec,
                  const std::string& ns,
+                 bool isReadCommitted,
                  int qopts = 0,
                  const BSONObj query = BSONObj(),
                  bool isAggCursor = false);
 
     /**
      * This ClientCursor is used to track sharding state for the given collection.
+     *
+     * Do not use outside of RangePreserver!
      */
     explicit ClientCursor(const Collection* collection);
 
@@ -81,6 +84,9 @@ public:
     CursorManager* cursorManager() const {
         return _cursorManager;
     }
+    bool isReadCommitted() const {
+        return _isReadCommitted;
+    }
     bool isAggCursor() const {
         return _isAggCursor;
     }
@@ -180,49 +186,6 @@ public:
 
     static long long totalOpen();
 
-    //
-    // Storage engine state for getMore.
-    //
-
-    bool hasRecoveryUnit() const {
-        return _ownedRU.get() || _unownedRU;
-    }
-
-    /**
-     *
-     * If a ClientCursor is created via DBDirectClient, it uses the same storage engine
-     * context as the DBDirectClient caller.  We store this context in _unownedRU.  We use
-     * this to verify that all further callers use the same RecoveryUnit.
-     *
-     * Once a ClientCursor has an unowned RecoveryUnit, it will always have one.
-     *
-     * Sets the unowned RecoveryUnit to 'ru'.  Does NOT take ownership of the pointer.
-     */
-    void setUnownedRecoveryUnit(RecoveryUnit* ru);
-
-    /**
-     * Return the unowned RecoveryUnit.  'this' does not own pointer and therefore cannot
-     * transfer ownership.
-     */
-    RecoveryUnit* getUnownedRecoveryUnit() const;
-
-    /**
-     * If a ClientCursor is created via a client request, we bind its lifetime to the
-     * ClientCursor's by storing it un _ownedRU.  In order to execute the query over repeated
-     * network requests, we have to keep the execution state around.
-     */
-
-    /**
-     * Set the owned recovery unit to 'ru'.  Takes ownership of it.  If there is a previous
-     * owned recovery unit, it is deleted.
-     */
-    void setOwnedRecoveryUnit(RecoveryUnit* ru);
-
-    /**
-     * Returns the owned recovery unit.  Ownership is transferred to the caller.
-     */
-    RecoveryUnit* releaseOwnedRecoveryUnit();
-
 private:
     friend class CursorManager;
     friend class ClientCursorPin;
@@ -248,6 +211,8 @@ private:
     // The namespace we're operating on.
     std::string _ns;
 
+    const bool _isReadCommitted;
+
     CursorManager* _cursorManager;
 
     // if we've added it to the total open counter yet
@@ -270,7 +235,7 @@ private:
     // should not be killed or destroyed when the underlying collection is deleted.
     //
     // Note: This should *not* be set for the internal cursor used as input to an aggregation.
-    bool _isAggCursor;
+    const bool _isAggCursor;
 
     // Is this cursor in use?  Defaults to false.
     bool _isPinned;
@@ -288,13 +253,6 @@ private:
     // TODO: Document.
     uint64_t _leftoverMaxTimeMicros;
 
-    // Only one of these is not-NULL.
-    RecoveryUnit* _unownedRU;
-    std::unique_ptr<RecoveryUnit> _ownedRU;
-    // NOTE: _ownedRU must come before _exec, because _ownedRU must outlive _exec.
-    // The storage engine can have resources in the PlanExecutor that rely on
-    // the RecoveryUnit being alive.
-
     //
     // The underlying execution machinery.
     //
-- 
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