diff --git a/lib/rdoc/generator/template/rails/resources/js/search.js b/lib/rdoc/generator/template/rails/resources/js/search.js
index f02a330f..0e8e7357 100644
--- a/lib/rdoc/generator/template/rails/resources/js/search.js
+++ b/lib/rdoc/generator/template/rails/resources/js/search.js
@@ -37,17 +37,17 @@ export class Search {
   }
 
   compileQuery(query) {
+    query = ` ${query} `;
     const bitPositions = [];
 
-    for (let i = 0, len = query.length; i < len; i += 1) {
-      const ngram = i === 0 ? (" " + query[0]) : query.substring(i - 1, i + 1);
+    for (let i = 0, upto = query.length - 2; i < upto; i += 1) {
+      const ngram = query.substring(i, i + 3);
       const position = searchIndex.ngrams[ngram];
 
       if (position) {
         bitPositions.push(position);
       }
     }
-
     return bitPositions;
   }
 
diff --git a/lib/sdoc/search_index.rb b/lib/sdoc/search_index.rb
index 50dd6538..97bde191 100644
--- a/lib/sdoc/search_index.rb
+++ b/lib/sdoc/search_index.rb
@@ -43,26 +43,23 @@ def derive_ngrams(name)
     # Example: "ActiveSupport::Cache::Store" => ":ActiveSupport:Cache:Store"
     strings = [":#{name}".gsub("::", ":")]
 
+    # Example: ":ActiveSupport:Cache:lookup_store" => ":ActiveSupport:Cache.lookup_store("
+    strings.concat(strings.map { |string| string.gsub(/[:#]([^A-Z].+)/, '.\1(') })
     # Example: ":ActiveModel:API" => ":activemodel:api"
     strings.concat(strings.map(&:downcase))
     # Example: ":ActiveSupport:HashWithIndifferentAccess" => ":AS:HWIA"
     strings.concat(strings.map { |string| string.gsub(/([A-Z])[a-z]+/, '\1') })
     # Example: ":AbstractController:Base#action_name" => " AbstractController Base action_name"
     strings.concat(strings.map { |string| string.tr(":#", " ") })
-    # Example: ":AbstractController:Base#action_name" => ":AbstractController:Base#actionname"
+    # Example: ":ActiveRecord:Querying#find_by_sql" => ":ActiveRecord:Querying#findbysql"
     strings.concat(strings.map { |string| string.tr("_", "") })
 
     # Example: ":ActiveModel:Name#<=>" => [":ActiveModel", ":Name", "#<=>"]
-    strings.map! { |string| string.split(/(?=[ :#])/) }.flatten!
+    strings.map! { |string| string.split(/(?=[ :#.])/) }.flatten!.uniq!
+    # Example: ":ActiveModel" => ":A "
+    strings.concat(strings.map { |string| "#{string[0, 2]} " })
 
-    if method_name_first_char = name[/(?:#|::)([^A-Z])/, 1]
-      # Example: "AbstractController::Base::controller_path" => ".c"
-      strings << ".#{method_name_first_char}"
-      # Example: "AbstractController::Base::controller_path" => "h("
-      strings << "#{name[-1]}("
-    end
-
-    strings.flat_map { |string| string.each_char.each_cons(2).map(&:join) }.uniq
+    strings.flat_map { |string| string.each_char.each_cons(3).map(&:join) }.uniq
   end
 
   def compile_ngrams(ngram_sets)
diff --git a/spec/search_index_spec.rb b/spec/search_index_spec.rb
index 0c992341..07d2ede8 100644
--- a/spec/search_index_spec.rb
+++ b/spec/search_index_spec.rb
@@ -49,58 +49,76 @@ def hoge_fuga; end
 
   describe "#derive_ngrams" do
     it "returns ngrams for a given string" do
-      expected = %w[ab bc cx xy yz]
+      expected = %w[abc bcx cxy xyz]
       _(SDoc::SearchIndex.derive_ngrams("abcxyz") & expected).must_equal expected
     end
 
     it "includes module-related ngrams" do
       ngrams = SDoc::SearchIndex.derive_ngrams("Abc::Xyz")
 
-      _(ngrams).must_include ":A"
-      _(ngrams).must_include ":X"
+      _(ngrams).must_include ":Ab"
+      _(ngrams).must_include ":Xy"
 
-      _(ngrams).wont_include "c:"
-      _(ngrams).wont_include "::"
+      _(ngrams.grep(/c:|::|[.(]/)).must_be_empty
     end
 
-    it "includes method-related ngrams" do
+    it "includes method-related ngrams for instance methods" do
       ngrams = SDoc::SearchIndex.derive_ngrams("Abc#def_xyz")
 
-      _(ngrams).must_include "#d"
-      _(ngrams).must_include ".d"
-      _(ngrams).must_include "z("
+      _(ngrams).must_include "#de"
+      _(ngrams).must_include ".de"
+      _(ngrams).must_include "yz("
 
-      _(ngrams).wont_include "c#"
+      _(ngrams).must_include "f_x"
+      _(ngrams).must_include "efx"
+      _(ngrams).must_include "fxy"
 
-      _(ngrams).must_include "f_"
-      _(ngrams).must_include "_x"
-      _(ngrams).must_include "fx"
+      _(ngrams.grep(/c#/)).must_be_empty
+    end
+
+    it "includes method-related ngrams for singleton methods" do
+      ngrams = SDoc::SearchIndex.derive_ngrams("Abc::def_xyz")
+
+      _(ngrams).must_include ":de"
+      _(ngrams).must_include ".de"
+      _(ngrams).must_include "yz("
+
+      _(ngrams.grep(/c:/)).must_be_empty
     end
 
     it "includes space delimiter ngrams" do
       ngrams = SDoc::SearchIndex.derive_ngrams("Abc::Def#xyz")
 
-      _(ngrams).must_include " A"
-      _(ngrams).must_include " D"
-      _(ngrams).must_include " x"
+      _(ngrams).must_include " Ab"
+      _(ngrams).must_include " A "
+      _(ngrams).must_include ":A "
+
+      _(ngrams).must_include " De"
+      _(ngrams).must_include " D "
+      _(ngrams).must_include ":D "
+
+      _(ngrams).must_include " xy"
+      _(ngrams).must_include " x "
+      _(ngrams).must_include "#x "
 
-      _(ngrams).wont_include "c "
-      _(ngrams).wont_include "f "
+      _(ngrams.grep(/[cfz] $/)).must_be_empty
     end
 
     it "includes acronym ngrams" do
-      ngrams = SDoc::SearchIndex.derive_ngrams("AbcDefGhi::RstUvwXyz")
+      ngrams = SDoc::SearchIndex.derive_ngrams("AbcDef::StUvWxYz")
 
-      _(ngrams).must_include "AD"
-      _(ngrams).must_include "DG"
-      _(ngrams).must_include "RU"
-      _(ngrams).must_include "UX"
+      _(ngrams).must_include ":AD"
+      _(ngrams).must_include " AD"
+      _(ngrams).must_include ":SU"
+      _(ngrams).must_include " SU"
+      _(ngrams).must_include "SUW"
+      _(ngrams).must_include "UWY"
 
-      _(ngrams).wont_include "GR"
+      _(ngrams.grep(/DS/)).must_be_empty
     end
 
     it "includes downcased ngrams except for acronym ngrams" do
-      ngrams = SDoc::SearchIndex.derive_ngrams("AbcDefGhi::RstUvwXyz")
+      ngrams = SDoc::SearchIndex.derive_ngrams("AbcDef::StUvWxYz")
 
       ngrams.grep(/[A-Z]/).grep_v(/[A-Z]{2}/).each do |uppercase|
         _(ngrams).must_include uppercase.downcase
@@ -110,7 +128,7 @@ def hoge_fuga; end
 
   describe "#compile_ngrams" do
     it "assigns ngram bit positions based on ngram rarity" do
-      base_ngrams = ("aa".."zz").take(4)
+      base_ngrams = ("aaa".."zzz").take(4)
       ngram_sets = (0..3).map { |n| base_ngrams.drop(n) }
 
       _(SDoc::SearchIndex.compile_ngrams(ngram_sets)).
@@ -120,7 +138,7 @@ def hoge_fuga; end
 
   describe "#generate_fingerprint" do
     it "returns an array of bytes with bits set for the given ngrams" do
-      ngrams = ("aa".."zz").take(8)
+      ngrams = ("aaa".."zzz").take(8)
 
       packed_positions = ngrams.each_with_index.to_h
       _(SDoc::SearchIndex.generate_fingerprint(ngrams, packed_positions)).must_equal [0b11111111]
@@ -130,17 +148,17 @@ def hoge_fuga; end
     end
 
     it "omits trailing zero bytes" do
-      _(SDoc::SearchIndex.generate_fingerprint(["xx"], { "xx" => 0, "yy" => 100 })).must_equal [1]
+      _(SDoc::SearchIndex.generate_fingerprint(["xxx"], { "xxx" => 0, "yyy" => 100 })).must_equal [1]
     end
   end
 
   describe "#compute_bit_weights" do
     it "returns an array of weights" do
-      _(SDoc::SearchIndex.compute_bit_weights({ "xx" => 0, "yy" => 1 })).must_equal [1, 1]
+      _(SDoc::SearchIndex.compute_bit_weights({ "xxx" => 0, "yyy" => 1 })).must_equal [1, 1]
     end
 
     it "computes weights based on ngram content" do
-      ngram_bit_positions = { "xx" => 0, " x" => 1, ":X" => 2, "#x" => 3 }
+      ngram_bit_positions = { "xxx" => 0, " xx" => 1, ":Xx" => 2, "#xx" => 3 }
       bit_weights = SDoc::SearchIndex.compute_bit_weights(ngram_bit_positions)
 
       _(bit_weights.length).must_equal ngram_bit_positions.length
@@ -149,7 +167,7 @@ def hoge_fuga; end
     end
 
     it "orders weights by bit position" do
-      ngram_bit_positions = { "xx" => 0, " x" => 1, ":X" => 2, "#x" => 3 }
+      ngram_bit_positions = { "xxx" => 0, " xx" => 1, ":Xx" => 2, "#xx" => 3 }
       bit_weights = SDoc::SearchIndex.compute_bit_weights(ngram_bit_positions)
 
       reversed = ngram_bit_positions.reverse_each.to_h
@@ -160,7 +178,7 @@ def hoge_fuga; end
     end
 
     it "ignores alias ngrams" do
-      _(SDoc::SearchIndex.compute_bit_weights({ "#x" => 0, ".x" => 0}).length).must_equal 1
+      _(SDoc::SearchIndex.compute_bit_weights({ "#xx" => 0, ".xx" => 0}).length).must_equal 1
     end
   end