Repo created

libs/search/base/text_index/merger.hpp

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+#pragma once
+
+#include "search/base/text_index/reader.hpp"
+
+class FileWriter;
+
+namespace search_base
+{
+// Merges two on-disk text indexes and writes them to a new one.
+class TextIndexMerger
+{
+public:
+  // The merging process is as follows.
+  // 1. Dictionaries from both indexes are read into memory, merged
+  //    and written to disk.
+  // 2. One uint32_t per entry is reserved in memory to calculate the
+  //    offsets of the postings lists.
+  // 3. One token at a time, all postings for the token are read from
+  //    both indexes into memory, unified and written to disk.
+  // 4. The offsets are written to disk.
+  //
+  // Note that the dictionary and offsets are kept in memory during the whole
+  // merging process.
+  static void Merge(TextIndexReader const & index1, TextIndexReader const & index2, FileWriter & sink);
+};
+}  // namespace search_base