1 files changed, 110 insertions, 0 deletions
diff --git a/src/mongo/db/exec/skip.cpp b/src/mongo/db/exec/skip.cpp
new file mode 100644
index 00000000000..04eaf4ae140
--- /dev/null
+++ b/src/mongo/db/exec/skip.cpp
@@ -0,0 +1,110 @@
+/**
+*    Copyright (C) 2013 10gen Inc.
+*
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*
+*    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
+*    GNU Affero General Public License for more details.
+*
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*
+*    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 GNU Affero General 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/db/exec/skip.h"
+#include "mongo/db/exec/working_set_common.h"
+#include "mongo/util/mongoutils/str.h"
+
+namespace mongo {
+
+    SkipStage::SkipStage(int toSkip, WorkingSet* ws, PlanStage* child)
+        : _ws(ws), _child(child), _toSkip(toSkip) { }
+
+    SkipStage::~SkipStage() { }
+
+    bool SkipStage::isEOF() { return _child->isEOF(); }
+
+    PlanStage::StageState SkipStage::work(WorkingSetID* out) {
+        ++_commonStats.works;
+
+        WorkingSetID id = WorkingSet::INVALID_ID;
+        StageState status = _child->work(&id);
+
+        if (PlanStage::ADVANCED == status) {
+            // If we're still skipping results...
+            if (_toSkip > 0) {
+                // ...drop the result.
+                --_toSkip;
+                _ws->free(id);
+                ++_commonStats.needTime;
+                return PlanStage::NEED_TIME;
+            }
+
+            *out = id;
+            ++_commonStats.advanced;
+            return PlanStage::ADVANCED;
+        }
+        else if (PlanStage::FAILURE == status) {
+            *out = id;
+            // If a stage fails, it may create a status WSM to indicate why it
+            // failed, in which case 'id' is valid.  If ID is invalid, we
+            // create our own error message.
+            if (WorkingSet::INVALID_ID == id) {
+                mongoutils::str::stream ss;
+                ss << "skip stage failed to read in results from child";
+                Status status(ErrorCodes::InternalError, ss);
+                *out = WorkingSetCommon::allocateStatusMember( _ws, status);
+            }
+            return status;
+        }
+        else {
+            if (PlanStage::NEED_FETCH == status) {
+                *out = id;
+                ++_commonStats.needFetch;
+            }
+            else if (PlanStage::NEED_TIME == status) {
+                ++_commonStats.needTime;
+            }
+            // NEED_TIME/YIELD, ERROR, IS_EOF
+            return status;
+        }
+    }
+
+    void SkipStage::prepareToYield() {
+        ++_commonStats.yields;
+        _child->prepareToYield();
+    }
+
+    void SkipStage::recoverFromYield() {
+        ++_commonStats.unyields;
+        _child->recoverFromYield();
+    }
+
+    void SkipStage::invalidate(const DiskLoc& dl, InvalidationType type) {
+        ++_commonStats.invalidates;
+        _child->invalidate(dl, type);
+    }
+
+    PlanStageStats* SkipStage::getStats() {
+        _commonStats.isEOF = isEOF();
+        auto_ptr<PlanStageStats> ret(new PlanStageStats(_commonStats, STAGE_SKIP));
+        ret->children.push_back(_child->getStats());
+        return ret.release();
+    }
+
+}  // namespace mongo