1 files changed, 54 insertions, 0 deletions
diff --git a/searchlib/src/vespa/searchlib/diskindex/field_merger.h b/searchlib/src/vespa/searchlib/diskindex/field_merger.h
new file mode 100644
index 00000000000..31c2818cf17
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/diskindex/field_merger.h
@@ -0,0 +1,54 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <vespa/vespalib/stllike/string.h>
+#include <cstdint>
+#include <memory>
+#include <vector>
+
+namespace search {
+class IFlushToken;
+template <class IN> class PostingPriorityQueue;
+}
+
+namespace search::index { class FieldLengthInfo; }
+
+namespace search::diskindex {
+
+class DictionaryWordReader;
+class FieldLengthScanner;
+class FieldReader;
+class FieldWriter;
+class FusionOutputIndex;
+class WordNumMapping;
+
+/*
+ * Class for merging posting lists for a single field during fusion.
+ */
+class FieldMerger
+{
+    using WordNumMappingList = std::vector<WordNumMapping>;
+
+    uint32_t                 _id;
+    vespalib::string         _field_dir;
+    const FusionOutputIndex& _fusion_out_index;
+
+    void make_tmp_dirs();
+    bool clean_tmp_dirs();
+    bool open_input_word_readers(std::vector<std::unique_ptr<DictionaryWordReader>>& readers, PostingPriorityQueue<DictionaryWordReader>& heap);
+    bool read_mapping_files(WordNumMappingList& list);
+    bool renumber_word_ids(WordNumMappingList& list, uint64_t& numWordIds, const IFlushToken& flush_token);
+    std::shared_ptr<FieldLengthScanner> allocate_field_length_scanner();
+    bool open_input_field_readers(const WordNumMappingList& list, std::vector<std::unique_ptr<FieldReader>>& readers);
+    bool open_field_writer(FieldWriter& writer, const index::FieldLengthInfo& field_length_info);
+    bool select_cooked_or_raw_features(FieldReader& reader, FieldWriter& writer);
+    bool setup_merge_heap(const std::vector<std::unique_ptr<FieldReader>>& readers, FieldWriter& writer, PostingPriorityQueue<FieldReader>& heap);
+    bool merge_postings(const WordNumMappingList& list, uint64_t numWordIds, const IFlushToken& flush_token);
+public:
+    FieldMerger(uint32_t id, const FusionOutputIndex& fusion_out_index);
+    ~FieldMerger();
+    bool merge_field(std::shared_ptr<IFlushToken> flush_token);
+};
+
+}