[clangd] Build Dex index after loading all shards in BackgroundIndex.

[hokein]

Summary

Currently after loadding all shards, we use MemIndex which has poor query
performance, we should use Dex.

[kadircet]

clangd/index/Background.cpp

609

could you run clang-format

[hokein]

Format the code.

clangd/index/Background.cpp

while (true) {
     if (!SymbolsUpdatedSinceLastIndex.exchange(false))
       continue;
     // There can be symbol update right after the flag is reset above and before
     // index is rebuilt below. The new index would contain the updated symbols
     // but the flag would still be true. This is fine as we would simply run an
     // extra index build.
     reset(
         IndexedSymbols.buildIndex(IndexType::Heavy, DuplicateHandling::Merge));
-    log("BackgroundIndex: rebuilt symbol index.");
+    log("BackgroundIndex: rebuilt symbol index with estimated memory {0} "
+        "bytes.",
+        estimateMemoryUsage());
   }
 }
 
 llvm::Error BackgroundIndex::index(tooling::CompileCommand Cmd,
                                    BackgroundIndexStorage *IndexStorage) {
   trace::Span Tracer("BackgroundIndex");
   SPAN_ATTACH(Tracer, "file", Cmd.Filename);
   auto AbsolutePath = getAbsolutePath(Cmd);
for (const auto &Dependency : Dependencies) {
       // Mark all of this TU's dependencies as to-be-indexed so that we won't
       // try to re-index those.
       for (const auto &Dependency : Dependencies)
         FilesToIndex.insert(Dependency.Path);
       break;
     }
   }
   vlog("Loaded all shards");
-  reset(IndexedSymbols.buildIndex(IndexType::Light, DuplicateHandling::Merge));
-
+  reset(IndexedSymbols.buildIndex(IndexType::Heavy, DuplicateHandling::Merge));
+  vlog("BackgroundIndex: built symbol index with estimated memory {0} "
+        "bytes.",
+        estimateMemoryUsage());
   return NeedsReIndexing;
 }
 
 } // namespace clangd
 } // namespace clang