Index: include-fixer/find-all-symbols/SymbolInfo.h
===================================================================
--- include-fixer/find-all-symbols/SymbolInfo.h
+++ include-fixer/find-all-symbols/SymbolInfo.h
@@ -54,6 +54,8 @@
              int LineNumber, const std::vector<Context> &Contexts,
              unsigned NumOccurrences = 0);
 
+  void SetFilePath(llvm::StringRef Path) { FilePath = Path; }
+
   /// \brief Get symbol name.
   llvm::StringRef getName() const { return Name; }
 
Index: include-fixer/tool/ClangIncludeFixer.cpp
===================================================================
--- include-fixer/tool/ClangIncludeFixer.cpp
+++ include-fixer/tool/ClangIncludeFixer.cpp
@@ -98,6 +98,12 @@
                            cl::desc("String to initialize the database"),
                            cl::cat(IncludeFixerCategory));
 
+cl::opt<std::string>
+    QuerySymbol("query-symbol",
+                 cl::desc("Query a given symbol (e.g. \"a::b::foo\") in\n"
+                          "database directly without parsing the file."),
+                 cl::cat(IncludeFixerCategory));
+
 cl::opt<bool>
     MinimizeIncludePaths("minimize-paths",
                          cl::desc("Whether to minimize added include paths"),
@@ -236,6 +242,7 @@
   tooling::ClangTool tool(options.getCompilations(),
                           options.getSourcePathList());
 
+  llvm::StringRef SourceFilePath = options.getSourcePathList().front();
   // In STDINMode, we override the file content with the <stdin> input.
   // Since `tool.mapVirtualFile` takes `StringRef`, we define `Code` outside of
   // the if-block so that `Code` is not released after the if-block.
@@ -253,7 +260,7 @@
     if (Code->getBufferSize() == 0)
       return 0;  // Skip empty files.
 
-    tool.mapVirtualFile(options.getSourcePathList().front(), Code->getBuffer());
+    tool.mapVirtualFile(SourceFilePath, Code->getBuffer());
   }
 
   if (!InsertHeader.empty()) {
@@ -314,10 +321,31 @@
 
   // Set up data source.
   std::unique_ptr<include_fixer::SymbolIndexManager> SymbolIndexMgr =
-      createSymbolIndexManager(options.getSourcePathList().front());
+      createSymbolIndexManager(SourceFilePath);
   if (!SymbolIndexMgr)
     return 1;
 
+  // Query symbol mode.
+  if (!QuerySymbol.empty()) {
+    auto MatchedSymbols = SymbolIndexMgr->search(QuerySymbol);
+    for (auto &Symbol : MatchedSymbols) {
+      std::string HeaderPath = Symbol.getFilePath().str();
+      Symbol.SetFilePath(((HeaderPath[0] == '"' || HeaderPath[0] == '<')
+                              ? HeaderPath
+                              : "\"" + HeaderPath + "\""));
+    }
+
+    // We leave an empty symbol range as we don't know the range of the symbol
+    // being queried in this mode. include-fixer won't add namespace qualifiers
+    // if the symbol range is empty, which also fits this case.
+    IncludeFixerContext::QuerySymbolInfo Symbol;
+    Symbol.RawIdentifier = QuerySymbol;
+    auto Context =
+        IncludeFixerContext(SourceFilePath, {Symbol}, MatchedSymbols);
+    writeToJson(llvm::outs(), Context);
+    return 0;
+  }
+
   // Now run our tool.
   std::vector<include_fixer::IncludeFixerContext> Contexts;
   include_fixer::IncludeFixerActionFactory Factory(*SymbolIndexMgr, Contexts,
Index: test/include-fixer/query_symbol.cpp
===================================================================
--- /dev/null
+++ test/include-fixer/query_symbol.cpp
@@ -0,0 +1,13 @@
+// RUN: clang-include-fixer -db=fixed -input='foo= "foo.h","bar.h"' -query-symbol="foo" test.cpp -- | FileCheck %s
+
+// CHECK:     "FilePath": "test.cpp",
+// CHECK-NEXT:"QuerySymbolInfos": [
+// CHECK-NEXT:   {"RawIdentifier": "foo",
+// CHECK-NEXT:    "Range":{"Offset":0,"Length":0}}
+// CHECK-NEXT:],
+// CHECK-NEXT:"HeaderInfos": [
+// CHECK-NEXT:  {"Header": "\"foo.h\"",
+// CHECK-NEXT:   "QualifiedName": "foo"},
+// CHECK-NEXT:  {"Header": "\"bar.h\"",
+// CHECK-NEXT:   "QualifiedName": "foo"}
+// CHECK-NEXT:]