Implement simple bitvector search cache for use in imported attribute vector.

1 files changed, 42 insertions, 0 deletions

diff --git a/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h b/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h
new file mode 100644
index 00000000000..4b6589459ca
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h
@@ -0,0 +1,42 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <vespa/vespalib/stllike/hash_map.h>
+#include <vespa/vespalib/stllike/string.h>
+#include <memory>
+#include <mutex>
+
+namespace search {
+
+class BitVector;
+
+namespace attribute {
+
+/**
+ * Class that caches posting lists (as bit vectors) for a set of search terms.
+ *
+ * Lifetime of cached bit vectors is controlled by calling clear() at regular intervals.
+ */
+class BitVectorSearchCache {
+public:
+    using BitVectorSP = std::shared_ptr<BitVector>;
+
+private:
+    using LockGuard = std::lock_guard<std::mutex>;
+    using Cache = vespalib::hash_map<vespalib::string, BitVectorSP>;
+
+    mutable std::mutex _mutex;
+    Cache _cache;
+
+public:
+    BitVectorSearchCache();
+    ~BitVectorSearchCache();
+    void insert(const vespalib::string &term, BitVectorSP bitVector);
+    BitVectorSP find(const vespalib::string &term) const;
+    size_t size() const;
+    void clear();
+};
+
+}
+}