Add search::predicate::SimpleIndexSaver.

Remove extra logging when saving predicate attribute.

14 files changed, 163 insertions, 115 deletions

diff --git a/searchlib/src/tests/predicate/predicate_index_test.cpp b/searchlib/src/tests/predicate/predicate_index_test.cpp
index 8e72fc1dbd9..40b650e489a 100644
--- a/searchlib/src/tests/predicate/predicate_index_test.cpp
+++ b/searchlib/src/tests/predicate/predicate_index_test.cpp
@@ -292,8 +292,7 @@ TEST("require that PredicateIndex can be (de)serialized") {
     index.commit();
 
     vespalib::DataBuffer buffer;
-    PredicateIndex::SerializeStats dummy_stats;
-    index.serialize(buffer, dummy_stats);
+    index.serialize(buffer);
     uint32_t doc_id_limit;
     DocIdLimitFinder finder(doc_id_limit);
     PredicateIndex index2(generation_holder, dummy_provider, simple_index_config,
@@ -337,8 +336,7 @@ TEST("require that DocumentFeaturesStore is restored on deserialization") {
     EXPECT_FALSE(index.getIntervalIndex().lookup(hash).valid());
     indexFeature(index, doc_id, min_feature, {{hash, interval}}, {{hash2, bounds}});
     vespalib::DataBuffer buffer;
-    PredicateIndex::SerializeStats dummy_stats;
-    index.serialize(buffer, dummy_stats);
+    index.serialize(buffer);
     uint32_t doc_id_limit;
     DocIdLimitFinder finder(doc_id_limit);
     PredicateIndex index2(generation_holder, dummy_provider, simple_index_config,
diff --git a/searchlib/src/tests/predicate/simple_index_test.cpp b/searchlib/src/tests/predicate/simple_index_test.cpp
index c37d377e668..9b99ff8e809 100644
--- a/searchlib/src/tests/predicate/simple_index_test.cpp
+++ b/searchlib/src/tests/predicate/simple_index_test.cpp
@@ -2,6 +2,9 @@
 // Unit tests for simple_index.
 
 #include <vespa/searchlib/predicate/simple_index.hpp>
+#include <vespa/searchlib/predicate/simple_index_saver.hpp>
+#include <vespa/searchlib/predicate/nbo_write.h>
+#include <vespa/searchlib/util/data_buffer_writer.h>
 #include <vespa/vespalib/testkit/testapp.h>
 #include <vespa/searchlib/attribute/predicate_attribute.h>
 #include <vespa/vespalib/btree/btree.hpp>
@@ -31,9 +34,9 @@ struct MyData {
     }
 };
 
-struct MyDataSerializer : PostingSerializer<MyData> {
-    void serialize(const MyData &data, vespalib::DataBuffer& buffer) const override {
-        buffer.writeInt32(data.data);
+struct MyDataSaver : PostingSaver<MyData> {
+    void save(const MyData &data, BufferWriter& writer) const override {
+        nbo_write<uint32_t>(writer, data.data);
     }
 };
 
@@ -176,8 +179,11 @@ TEST_FF("require that SimpleIndex can be serialized and deserialized.", Fixture,
     }
     f1.commit();
     vespalib::DataBuffer buffer;
-    SimpleIndex<MyData>::SerializeStats dummy_stats;
-    f1.index().serialize(buffer, MyDataSerializer(), dummy_stats);
+    {
+        DataBufferWriter writer(buffer);
+        f1.index().make_saver(std::make_unique<MyDataSaver>())->save(writer);
+        writer.flush();
+    }
     MyObserver observer;
     MyDataDeserializer deserializer;
     f2.index().deserialize(buffer, deserializer, observer, PredicateAttribute::PREDICATE_ATTRIBUTE_VERSION);
diff --git a/searchlib/src/vespa/searchlib/attribute/predicate_attribute.cpp b/searchlib/src/vespa/searchlib/attribute/predicate_attribute.cpp
index 1f596699bca..ddf71063306 100644
--- a/searchlib/src/vespa/searchlib/attribute/predicate_attribute.cpp
+++ b/searchlib/src/vespa/searchlib/attribute/predicate_attribute.cpp
@@ -141,11 +141,8 @@ PredicateAttribute::before_inc_generation(generation_t current_gen)
 void
 PredicateAttribute::onSave(IAttributeSaveTarget &saveTarget) {
     LOG(info, "Saving predicate attribute version %d", getVersion());
-    vespalib::string name(getBaseFileName());
-    PredicateIndex::SerializeStats stats;
     IAttributeSaveTarget::Buffer buffer(saveTarget.datWriter().allocBuf(4_Ki));
-    _index->serialize(*buffer, stats);
-    size_t predicate_index_len = buffer->getDataLen();
+    _index->serialize(*buffer);
     uint32_t  highest_doc_id = static_cast<uint32_t>(_min_feature.size() - 1);
     buffer->writeInt32(highest_doc_id);
     for (size_t i = 1; i <= highest_doc_id; ++i) {
@@ -155,21 +152,6 @@ PredicateAttribute::onSave(IAttributeSaveTarget &saveTarget) {
         buffer->writeInt16(_interval_range_vector[i]);
     }
     buffer->writeInt16(_max_interval_range);
-    auto min_feature_and_interval_range_vector_len = buffer->getDataLen() - predicate_index_len;
-    auto total_len = buffer->getDataLen();
-    LOG(info, "Serialized predicate attribute %s: "
-        "{features=%zu, zeros=%zu, "
-        "interval={dictionary=%zu, btrees=%zu, bytes=%zu}, "
-        "interval_with_bounds={dictionary %zu, btrees=%zu, bytes=%zu}, "
-        "predicate-index_len=%zu, "
-        "min_feature and interval_range_vector=%zu, total=%zu}",
-        name.c_str(),
-        stats._features_len, stats._zeroes_len,
-        stats._interval._dictionary_size, stats._interval._btree_count, stats._interval._bytes,
-        stats._interval_with_bounds._dictionary_size, stats._interval_with_bounds._btree_count, stats._interval_with_bounds._bytes,
-        predicate_index_len,
-        min_feature_and_interval_range_vector_len,
-        total_len);
     saveTarget.datWriter().writeBuf(std::move(buffer));
 }
 
diff --git a/searchlib/src/vespa/searchlib/predicate/CMakeLists.txt b/searchlib/src/vespa/searchlib/predicate/CMakeLists.txt
index acb0391143d..48e79648675 100644
--- a/searchlib/src/vespa/searchlib/predicate/CMakeLists.txt
+++ b/searchlib/src/vespa/searchlib/predicate/CMakeLists.txt
@@ -11,6 +11,7 @@ vespa_add_library(searchlib_predicate OBJECT
     predicate_tree_annotator.cpp
     predicate_zero_constraint_posting_list.cpp
     simple_index.cpp
+    simple_index_saver.cpp
     common.cpp
     DEPENDS
 )
diff --git a/searchlib/src/vespa/searchlib/predicate/document_features_store_saver.cpp b/searchlib/src/vespa/searchlib/predicate/document_features_store_saver.cpp
index 08a3592da14..fcdb1afc652 100644
--- a/searchlib/src/vespa/searchlib/predicate/document_features_store_saver.cpp
+++ b/searchlib/src/vespa/searchlib/predicate/document_features_store_saver.cpp
@@ -1,8 +1,7 @@
 // Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 
 #include "document_features_store_saver.h"
-#include <vespa/searchlib/util/bufferwriter.h>
-#include <vespa/vespalib/objects/nbo.h>
+#include "nbo_write.h"
 
 using vespalib::datastore::EntryRef;
 using search::BufferWriter;
@@ -22,13 +21,6 @@ DocumentFeaturesStoreSaver::~DocumentFeaturesStoreSaver() = default;
 
 namespace {
 
-template <typename T>
-void nbo_write(BufferWriter& writer, T value)
-{
-    auto value_nbo = vespalib::nbo::n2h(value);
-    writer.write(&value_nbo, sizeof(value_nbo));
-}
-
 template <typename RefsVector, typename RangesStore>
 void
 find_used_words(const RefsVector& refs, const RangesStore& ranges,
diff --git a/searchlib/src/vespa/searchlib/predicate/nbo_write.h b/searchlib/src/vespa/searchlib/predicate/nbo_write.h
new file mode 100644
index 00000000000..fc5724a6012
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/predicate/nbo_write.h
@@ -0,0 +1,21 @@
+// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <vespa/searchlib/util/bufferwriter.h>
+#include <vespa/vespalib/objects/nbo.h>
+
+namespace search::predicate {
+
+/*
+ * Utility function for writing a scalar value
+ * in network byte order via an BufferWriter.
+ */
+template <typename T>
+void nbo_write(BufferWriter& writer, T value)
+{
+    auto value_nbo = vespalib::nbo::n2h(value);
+    writer.write(&value_nbo, sizeof(value_nbo));
+}
+
+}
diff --git a/searchlib/src/vespa/searchlib/predicate/predicate_index.cpp b/searchlib/src/vespa/searchlib/predicate/predicate_index.cpp
index 324e3fd99e8..296a6ff5c2e 100644
--- a/searchlib/src/vespa/searchlib/predicate/predicate_index.cpp
+++ b/searchlib/src/vespa/searchlib/predicate/predicate_index.cpp
@@ -3,6 +3,7 @@
 #include "predicate_index.h"
 #include "document_features_store_saver.h"
 #include "predicate_hash.h"
+#include "simple_index_saver.h"
 #include <vespa/searchlib/util/data_buffer_writer.h>
 #include <vespa/vespalib/datastore/buffer_type.hpp>
 #include <vespa/vespalib/btree/btree.hpp>
@@ -11,7 +12,6 @@
 #include <vespa/vespalib/btree/btreestore.hpp>
 #include <vespa/vespalib/btree/btreenodeallocator.hpp>
 
-
 using vespalib::datastore::EntryRef;
 using vespalib::DataBuffer;
 
@@ -44,20 +44,20 @@ PredicateIndex::indexDocumentFeatures(uint32_t doc_id, const PredicateIndex::Fea
 namespace {
 constexpr double THRESHOLD_USE_BIT_VECTOR_CACHE = 0.1;
 
-// PostingSerializer that writes intervals from interval store based
-// on the EntryRef that is to be serialized.
+// PostingSaver that writes intervals from interval store based
+// on the EntryRef that is to be saved.
 template <typename IntervalT>
-class IntervalSerializer : public PostingSerializer<EntryRef> {
+class IntervalSaver : public PostingSaver<EntryRef> {
     const PredicateIntervalStore &_store;
 public:
-    IntervalSerializer(const PredicateIntervalStore &store) : _store(store) {}
-    void serialize(const EntryRef &ref, DataBuffer &buffer) const override {
+    IntervalSaver(const PredicateIntervalStore &store) : _store(store) {}
+    void save(const EntryRef &ref, BufferWriter& writer) const override {
         uint32_t size;
         IntervalT single_buf;
         const IntervalT *interval = _store.get(ref, size, &single_buf);
-        buffer.writeInt16(size);
+        nbo_write<uint16_t>(writer, size);
         for (uint32_t i = 0; i < size; ++i) {
-            interval[i].serialize(buffer);
+            interval[i].save(writer);
         }
     }
 };
@@ -128,25 +128,26 @@ PredicateIndex::PredicateIndex(GenerationHolder &genHolder,
 PredicateIndex::~PredicateIndex() = default;
 
 void
-PredicateIndex::serialize(DataBuffer &buffer, SerializeStats& stats) const {
+PredicateIndex::serialize(DataBuffer &buffer) const {
     {
         auto saver = _features_store.make_saver();
         DataBufferWriter writer(buffer);
         saver->save(writer);
         writer.flush();
     }
-    stats._features_len = buffer.getDataLen();
-    auto old_len = buffer.getDataLen();
     buffer.writeInt16(_arity);
     buffer.writeInt32(_zero_constraint_docs.size());
     for (auto it = _zero_constraint_docs.begin(); it.valid(); ++it) {
         buffer.writeInt32(it.getKey());
     }
-    stats._zeroes_len = buffer.getDataLen() - old_len;
-    IntervalSerializer<Interval> interval_serializer(_interval_store);
-    _interval_index.serialize(buffer, interval_serializer, stats._interval);
-    IntervalSerializer<IntervalWithBounds> bounds_serializer(_interval_store);
-    _bounds_index.serialize(buffer, bounds_serializer, stats._interval_with_bounds);
+    {
+        DataBufferWriter writer(buffer);
+        auto interval_saver = _interval_index.make_saver(std::make_unique<IntervalSaver<Interval>>(_interval_store));
+        interval_saver->save(writer);
+        auto bounds_saver = _bounds_index.make_saver(std::make_unique<IntervalSaver<IntervalWithBounds>>(_interval_store));
+        bounds_saver->save(writer);
+        writer.flush();
+    }
 }
 
 void
diff --git a/searchlib/src/vespa/searchlib/predicate/predicate_index.h b/searchlib/src/vespa/searchlib/predicate/predicate_index.h
index 351fa3a1a9f..439187bccd7 100644
--- a/searchlib/src/vespa/searchlib/predicate/predicate_index.h
+++ b/searchlib/src/vespa/searchlib/predicate/predicate_index.h
@@ -37,19 +37,6 @@ public:
     using GenerationHolder = vespalib::GenerationHolder;
     using BTreeIterator = SimpleIndex<vespalib::datastore::EntryRef>::BTreeIterator;
     using VectorIterator = SimpleIndex<vespalib::datastore::EntryRef>::VectorIterator;
-    struct SerializeStats {
-        size_t _features_len;
-        size_t _zeroes_len;
-        IntervalIndex::SerializeStats _interval;
-        BoundsIndex::SerializeStats _interval_with_bounds;
-        SerializeStats()
-            : _features_len(0),
-              _zeroes_len(0),
-              _interval(),
-              _interval_with_bounds()
-        {
-        }
-    };
 private:
     uint32_t                  _arity;
     const DocIdLimitProvider &_limit_provider;
@@ -79,7 +66,7 @@ public:
                    SimpleIndexDeserializeObserver<> & observer, uint32_t version);
 
     ~PredicateIndex() override;
-    void serialize(vespalib::DataBuffer &buffer, SerializeStats& stats) const;
+    void serialize(vespalib::DataBuffer &buffer) const;
     void onDeserializationCompleted();
 
     void indexEmptyDocument(uint32_t doc_id);
diff --git a/searchlib/src/vespa/searchlib/predicate/predicate_interval.h b/searchlib/src/vespa/searchlib/predicate/predicate_interval.h
index 28cb17abd79..2023ec8560c 100644
--- a/searchlib/src/vespa/searchlib/predicate/predicate_interval.h
+++ b/searchlib/src/vespa/searchlib/predicate/predicate_interval.h
@@ -2,6 +2,7 @@
 
 #pragma once
 
+#include "nbo_write.h"
 #include <vespa/vespalib/data/databuffer.h>
 
 namespace search::predicate {
@@ -15,8 +16,8 @@ struct Interval {
     Interval() : interval(0) {}
     Interval(uint32_t interval_) : interval(interval_) {}
 
-    void serialize(vespalib::DataBuffer &buffer) const {
-        buffer.writeInt32(interval);
+    void save(BufferWriter& writer) const {
+        nbo_write<uint32_t>(writer, interval);
     }
     static Interval deserialize(vespalib::DataBuffer &buffer) {
         return Interval{buffer.readInt32()};
@@ -41,9 +42,9 @@ struct IntervalWithBounds {
     IntervalWithBounds() : interval(0), bounds(0) {}
     IntervalWithBounds(uint32_t interval_, uint32_t bounds_) : interval(interval_), bounds(bounds_) {}
 
-    void serialize(vespalib::DataBuffer &buffer) const {
-        buffer.writeInt32(interval);
-        buffer.writeInt32(bounds);
+    void save(BufferWriter& writer) const {
+        nbo_write<uint32_t>(writer, interval);
+        nbo_write<uint32_t>(writer, bounds);
     }
     static IntervalWithBounds deserialize(vespalib::DataBuffer &buffer) {
         uint32_t interval = buffer.readInt32();
diff --git a/searchlib/src/vespa/searchlib/predicate/simple_index.h b/searchlib/src/vespa/searchlib/predicate/simple_index.h
index 0fb6ce6e9db..1acfda24eeb 100644
--- a/searchlib/src/vespa/searchlib/predicate/simple_index.h
+++ b/searchlib/src/vespa/searchlib/predicate/simple_index.h
@@ -8,8 +8,12 @@
 #include <vespa/vespalib/util/rcuvector.h>
 #include <optional>
 
+namespace search { class BufferWriter; }
+
 namespace search::predicate {
 
+template <typename, typename, typename> class SimpleIndexSaver;
+
 template <typename Key = uint64_t, typename DocId = uint32_t>
 struct SimpleIndexDeserializeObserver {
     virtual ~SimpleIndexDeserializeObserver() {}
@@ -17,9 +21,9 @@ struct SimpleIndexDeserializeObserver {
 };
 
 template <typename Posting>
-struct PostingSerializer {
-    virtual ~PostingSerializer() {}
-    virtual void serialize(const Posting &posting, vespalib::DataBuffer &buffer) const = 0;
+struct PostingSaver {
+    virtual ~PostingSaver() {}
+    virtual void save(const Posting &posting, BufferWriter& writer) const = 0;
 };
 
 template <typename Posting>
@@ -136,17 +140,6 @@ public:
     using PostingVector = vespalib::RcuVectorBase<Posting>;
     using VectorStore = vespalib::btree::BTree<Key, std::shared_ptr<PostingVector>, vespalib::btree::NoAggregated>;
     using VectorIterator = PostingVectorIterator<Posting, Key, DocId>;
-    struct SerializeStats {
-        size_t _dictionary_size;
-        size_t _btree_count;
-        size_t _bytes;
-        SerializeStats()
-            : _dictionary_size(0),
-              _btree_count(0),
-              _bytes(0)
-        {
-        }
-    };
 
 private:
     using GenerationHolder = vespalib::GenerationHolder;
@@ -186,8 +179,6 @@ public:
         : _generation_holder(generation_holder), _config(config), _limit_provider(provider) {}
     ~SimpleIndex();
 
-    void serialize(vespalib::DataBuffer &buffer,
-                   const PostingSerializer<Posting> &serializer, SerializeStats& stats) const;
     void deserialize(vespalib::DataBuffer &buffer,
                      PostingDeserializer<Posting> &deserializer,
                      SimpleIndexDeserializeObserver<Key, DocId> &observer, uint32_t version);
@@ -226,6 +217,8 @@ public:
         return optional<VectorIterator>();
 
     }
+
+    std::unique_ptr<SimpleIndexSaver<Posting, Key, DocId>> make_saver(std::unique_ptr<PostingSaver<Posting>> subsaver) const;
 };
 
 template<typename Posting, typename Key, typename DocId>
diff --git a/searchlib/src/vespa/searchlib/predicate/simple_index.hpp b/searchlib/src/vespa/searchlib/predicate/simple_index.hpp
index 0b5c8cbdb62..b0a65622d86 100644
--- a/searchlib/src/vespa/searchlib/predicate/simple_index.hpp
+++ b/searchlib/src/vespa/searchlib/predicate/simple_index.hpp
@@ -2,6 +2,7 @@
 #pragma once
 
 #include "simple_index.h"
+#include "simple_index_saver.h"
 #include <vespa/vespalib/util/stringfmt.h>
 
 namespace search::predicate {
@@ -69,33 +70,6 @@ SimpleIndex<Posting, Key, DocId>::~SimpleIndex() {
 
 template <typename Posting, typename Key, typename DocId>
 void
-SimpleIndex<Posting, Key, DocId>::serialize(vespalib::DataBuffer &buffer, const PostingSerializer<Posting> &serializer, SerializeStats& stats) const {
-    assert(sizeof(Key) <= sizeof(uint64_t));
-    assert(sizeof(DocId) <= sizeof(uint32_t));
-    stats = SerializeStats();
-    stats._dictionary_size = _dictionary.size();
-    auto old_size = buffer.getDataLen();
-    buffer.writeInt32(_dictionary.size());
-    for (auto it = _dictionary.begin(); it.valid(); ++it) {
-        vespalib::datastore::EntryRef ref = it.getData();
-        buffer.writeInt32(_btree_posting_lists.size(ref));  // 0 if !valid()
-        auto posting_it = _btree_posting_lists.begin(ref);
-        if (!posting_it.valid())
-            continue;
-        if (posting_it.size() > 8u) {
-            ++stats._btree_count;
-        }
-        buffer.writeInt64(it.getKey());  // Key
-        for (; posting_it.valid(); ++posting_it) {
-            buffer.writeInt32(posting_it.getKey());  // DocId
-            serializer.serialize(posting_it.getData(), buffer);
-        }
-    }
-    stats._bytes = buffer.getDataLen() - old_size;
-}
-
-template <typename Posting, typename Key, typename DocId>
-void
 SimpleIndex<Posting, Key, DocId>::deserialize(vespalib::DataBuffer &buffer, PostingDeserializer<Posting> &deserializer,
                                               SimpleIndexDeserializeObserver<Key, DocId> &observer, uint32_t version)
 {
@@ -326,4 +300,11 @@ SimpleIndex<Posting, Key, DocId>::getMemoryUsage() const {
     return combined;
 };
 
+template <typename Posting, typename Key, typename DocId>
+std::unique_ptr<SimpleIndexSaver<Posting, Key, DocId>>
+SimpleIndex<Posting, Key, DocId>::make_saver(std::unique_ptr<PostingSaver<Posting>> subsaver) const
+{
+    return std::make_unique<SimpleIndexSaver<Posting, Key, DocId>>(_dictionary, _btree_posting_lists, std::move(subsaver));
+}
+
 }
diff --git a/searchlib/src/vespa/searchlib/predicate/simple_index_saver.cpp b/searchlib/src/vespa/searchlib/predicate/simple_index_saver.cpp
new file mode 100644
index 00000000000..9b080281347
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/predicate/simple_index_saver.cpp
@@ -0,0 +1,15 @@
+// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "simple_index_saver.hpp"
+#include <vespa/vespalib/btree/btree.hpp>
+#include <vespa/vespalib/btree/btreeroot.hpp>
+#include <vespa/vespalib/btree/btreeiterator.hpp>
+#include <vespa/vespalib/btree/btreestore.hpp>
+#include <vespa/vespalib/btree/btreenodeallocator.hpp>
+#include <vespa/vespalib/datastore/buffer_type.hpp>
+
+namespace search::predicate {
+
+template class SimpleIndexSaver<vespalib::datastore::EntryRef>;
+
+}
diff --git a/searchlib/src/vespa/searchlib/predicate/simple_index_saver.h b/searchlib/src/vespa/searchlib/predicate/simple_index_saver.h
new file mode 100644
index 00000000000..e312f42931d
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/predicate/simple_index_saver.h
@@ -0,0 +1,30 @@
+// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include "simple_index.h"
+
+namespace search::predicate {
+
+/*
+ * Class used to save a SimpleIndex instance, streaming the serialized
+ * data via a BufferWriter.
+ */
+template <typename Posting,
+          typename Key = uint64_t, typename DocId = uint32_t>
+class SimpleIndexSaver
+{
+    using Source = SimpleIndex<Posting,Key,DocId>;
+    using Dictionary = Source::Dictionary;
+    using BTreeStore = Source::BTreeStore;
+
+    const Dictionary& _dictionary;
+    const BTreeStore& _btree_posting_lists;
+    std::unique_ptr<PostingSaver<Posting>> _subsaver;
+public:
+    SimpleIndexSaver(const Dictionary& dictionary, const BTreeStore& btree_posting_lists, std::unique_ptr<PostingSaver<Posting>> _subsaver);
+    ~SimpleIndexSaver();
+    void save(BufferWriter& writer) const;
+};
+
+}
diff --git a/searchlib/src/vespa/searchlib/predicate/simple_index_saver.hpp b/searchlib/src/vespa/searchlib/predicate/simple_index_saver.hpp
new file mode 100644
index 00000000000..a3db21ca6cb
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/predicate/simple_index_saver.hpp
@@ -0,0 +1,40 @@
+// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "simple_index_saver.h"
+#include "nbo_write.h"
+
+namespace search::predicate {
+
+template <typename Posting, typename Key, typename DocId>
+SimpleIndexSaver<Posting, Key, DocId>::SimpleIndexSaver(const Dictionary& dictionary, const BTreeStore& btree_posting_lists, std::unique_ptr<PostingSaver<Posting>> subsaver)
+    : _dictionary(dictionary),
+      _btree_posting_lists(btree_posting_lists),
+      _subsaver(std::move(subsaver))
+{
+}
+
+template <typename Posting, typename Key, typename DocId>
+SimpleIndexSaver<Posting, Key, DocId>::~SimpleIndexSaver() = default;
+
+template <typename Posting, typename Key, typename DocId>
+void
+SimpleIndexSaver<Posting, Key, DocId>::save(BufferWriter& writer) const
+{
+    assert(sizeof(Key) <= sizeof(uint64_t));
+    assert(sizeof(DocId) <= sizeof(uint32_t));
+    nbo_write<uint32_t>(writer, _dictionary.size());
+    for (auto it = _dictionary.begin(); it.valid(); ++it) {
+        vespalib::datastore::EntryRef ref = it.getData();
+        auto posting_it = _btree_posting_lists.begin(ref);
+        nbo_write<uint32_t>(writer, posting_it.size());  // 0 if !valid()
+        if (!posting_it.valid())
+            continue;
+        nbo_write<uint64_t>(writer, it.getKey());  // Key
+        for (; posting_it.valid(); ++posting_it) {
+            nbo_write<uint32_t>(writer, posting_it.getKey());  // DocId
+            _subsaver->save(posting_it.getData(), writer);
+        }
+    }
+}
+
+}