SERVER-17656: First pass implementation of partial indexes

1 files changed, 50 insertions, 0 deletions

diff --git a/src/mongo/db/matcher/expression_algo.h b/src/mongo/db/matcher/expression_algo.h
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index 00000000000..8e3b7bd701c
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+++ b/src/mongo/db/matcher/expression_algo.h
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+// expression_algo.h
+
+/**
+ *    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 MatchExpression;
+
+    namespace expression {
+        /**
+         * In filtered index case, a is the query, b is the filter.
+         * @return If 'b' cannot reduce the set of returned documents that would
+         *         be returned with 'a' as the only filter.
+         *         Everything that matches a also must match b.
+         *         The document set returned by applying a is a subset of the document
+         *         set returned by applying b.
+         * Examples:
+         *    a: { x : 5 } b: { x : { $lte : 5 } } = true
+         *    a: { x : { $lte : 5 } b: { x : 5 } = false
+         */
+        bool isClauseRedundant(const MatchExpression* a,
+                               const MatchExpression* b);
+    }
+}