SERVER-18771 implement getMore command on mongos

1 files changed, 63 insertions, 0 deletions

diff --git a/src/mongo/db/query/find_common.h b/src/mongo/db/query/find_common.h
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+++ b/src/mongo/db/query/find_common.h
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+/**
+ *    Copyright (C) 2015 MongoDB 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.
+ */
+
+namespace mongo {
+
+class LiteParsedQuery;
+
+/**
+ * Suite of find/getMore related functions used in both the mongod and mongos query paths.
+ */
+class FindCommon {
+public:
+    // The size threshold at which we stop adding result documents to a getMore response or a find
+    // response that has a batchSize set (i.e. once the sum of the document sizes in bytes exceeds
+    // this value, no further documents are added).
+    static const int kMaxBytesToReturnToClientAtOnce = 4 * 1024 * 1024;
+
+    /**
+     * Returns true if enough results have been prepared to stop adding more to the first batch.
+     *
+     * If 'pq' does not have a batchSize, the default batchSize is respected.
+     */
+    static bool enoughForFirstBatch(const LiteParsedQuery& pq,
+                                    long long numDocs,
+                                    int bytesBuffered);
+
+    /**
+     * Returns true if enough results have been prepared to stop adding more to a getMore batch.
+     *
+     * An 'ntoreturn' value of zero is interpreted as the absence of a batchSize; in this case,
+     * returns true only once the size threshold is exceeded. If 'ntoreturn' is positive, returns
+     * true once either are added until we have either satisfied the batch size or exceeded the size
+     * threshold.
+     */
+    static bool enoughForGetMore(long long ntoreturn, long long numDocs, int bytesBuffered);
+};
+
+}  // namespace mongo