SERVER-17659 Add PlanCacheIndexabilityState

Encapsulates functionality to be used by PlanCache, for deciding how
to cache queries with predicates over elements in partial index key
patterns.

1 files changed, 82 insertions, 0 deletions

diff --git a/src/mongo/db/query/plan_cache_indexability.cpp b/src/mongo/db/query/plan_cache_indexability.cpp
new file mode 100644
index 00000000000..ace1c9c278d
--- /dev/null
+++ b/src/mongo/db/query/plan_cache_indexability.cpp
@@ -0,0 +1,82 @@
+/**
+ *    Copyright (C) 2015 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/platform/basic.h"
+
+#include "mongo/db/query/plan_cache_indexability.h"
+
+#include <memory>
+#include "mongo/base/init.h"
+#include "mongo/base/owned_pointer_vector.h"
+#include "mongo/db/query/index_entry.h"
+#include "mongo/db/matcher/expression.h"
+#include "mongo/db/matcher/expression_algo.h"
+#include "mongo/db/matcher/expression_leaf.h"
+#include "mongo/stdx/memory.h"
+
+namespace mongo {
+
+    void PlanCacheIndexabilityState::processPartialIndex(const MatchExpression* filterExpr) {
+        invariant(filterExpr);
+        for (size_t i = 0; i < filterExpr->numChildren(); ++i) {
+            processPartialIndex(filterExpr->getChild(i));
+        }
+        if (!filterExpr->isLogical()) {
+            _pathDiscriminatorsMap[filterExpr->path()].push_back(
+                [filterExpr] (const MatchExpression* queryExpr) {
+                    return expression::isClauseRedundant(queryExpr, filterExpr);
+                }
+            );
+        }
+    }
+
+namespace {
+    const IndexabilityDiscriminators emptyDiscriminators;
+}  // namespace
+
+    const IndexabilityDiscriminators& PlanCacheIndexabilityState::getDiscriminators(
+            StringData path) const {
+        PathDiscriminatorsMap::const_iterator it = _pathDiscriminatorsMap.find(path);
+        if (it == _pathDiscriminatorsMap.end()) {
+            return emptyDiscriminators;
+        }
+        return it->second;
+    }
+
+    void PlanCacheIndexabilityState::updateDiscriminators(
+            const std::vector<IndexEntry>& indexEntries) {
+        _pathDiscriminatorsMap = PathDiscriminatorsMap();
+
+        for (const IndexEntry& idx : indexEntries) {
+            if (idx.filterExpr) {
+                processPartialIndex(idx.filterExpr);
+            }
+        }
+    }
+
+}  // namespace mongo