[PATCH] D51287: [clangd] Use TRUE iterator instead of complete posting list

Kirill Bobyrev via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Mon Aug 27 01:52:55 PDT 2018

kbobyrev created this revision.
kbobyrev added a reviewer: ilya-biryukov.
kbobyrev added a project: clang-tools-extra.
Herald added subscribers: kadircet, arphaman, jkorous, MaskRay.
kbobyrev edited the summary of this revision.

Stop using `$$$` (empty) trigram and generating a posting list with all items. Since TRUE iterator is already implemented and correctly inserted when there are no real trigram posting lists, this is a valid transformation.

Benchmarks show that this simple change allows ~30% speedup on dataset of real completion queries.


  Benchmark                Time           CPU Iterations
  DexAdHocQueries    5640321 ns    5640265 ns        120
  DexRealQ         939835603 ns  939830296 ns          1


  Benchmark                Time           CPU Iterations
  DexAdHocQueries    3452014 ns    3451987 ns        203
  DexRealQ         667455912 ns  667455750 ns          1



Index: clang-tools-extra/clangd/index/dex/Trigram.cpp
--- clang-tools-extra/clangd/index/dex/Trigram.cpp
+++ clang-tools-extra/clangd/index/dex/Trigram.cpp
@@ -67,10 +67,6 @@
     UniqueTrigrams.insert(Token(Token::Kind::Trigram, Chars));
-  // FIXME(kbobyrev): Instead of producing empty trigram for each identifier,
-  // just use True Iterator on the query side when the query string is empty.
   if (TwoHeads.size() == 2)
     add({{TwoHeads.front(), TwoHeads.back(), END_MARKER}});

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