diff --git a/autoload/ale/c.vim b/autoload/ale/c.vim
index 617e81f6..746d19b0 100644
--- a/autoload/ale/c.vim
+++ b/autoload/ale/c.vim
@@ -157,15 +157,17 @@ if !exists('s:compile_commands_cache')
     let s:compile_commands_cache = {}
 endif
 
-function! s:GetListFromCompileCommandsFile(compile_commands_file) abort
+function! s:GetLookupFromCompileCommandsFile(compile_commands_file) abort
+    let l:empty = [{}, {}]
+
     if empty(a:compile_commands_file)
-        return []
+        return l:empty
     endif
 
     let l:time = getftime(a:compile_commands_file)
 
     if l:time < 0
-        return []
+        return l:empty
     endif
 
     let l:key = a:compile_commands_file . ':' . l:time
@@ -174,21 +176,36 @@ function! s:GetListFromCompileCommandsFile(compile_commands_file) abort
         return s:compile_commands_cache[l:key]
     endif
 
-    let l:data = []
-    silent! let l:data = json_decode(join(readfile(a:compile_commands_file), ''))
+    let l:raw_data = []
+    silent! let l:raw_data = json_decode(join(readfile(a:compile_commands_file), ''))
 
-    if !empty(l:data)
-        let s:compile_commands_cache[l:key] = l:data
+    let l:file_lookup = {}
+    let l:dir_lookup = {}
 
-        return l:data
+    for l:entry in l:raw_data
+        let l:basename = tolower(fnamemodify(l:entry.file, ':t'))
+        let l:file_lookup[l:basename] = get(l:file_lookup, l:basename, []) + [l:entry]
+
+        let l:dirbasename = tolower(fnamemodify(l:entry.directory, ':p:h:t'))
+        let l:dir_lookup[l:dirbasename] = get(l:dir_lookup, l:basename, []) + [l:entry]
+    endfor
+
+    if !empty(l:file_lookup) && !empty(l:dir_lookup)
+        let l:result = [l:file_lookup, l:dir_lookup]
+        let s:compile_commands_cache[l:key] = l:result
+
+        return l:result
     endif
 
-    return []
+    return l:empty
 endfunction
 
-function! ale#c#ParseCompileCommandsFlags(buffer, dir, json_list) abort
+function! ale#c#ParseCompileCommandsFlags(buffer, dir, file_lookup, dir_lookup) abort
     " Search for an exact file match first.
-    for l:item in a:json_list
+    let l:basename = tolower(expand('#' . a:buffer . ':t'))
+    let l:file_list = get(a:file_lookup, l:basename, [])
+
+    for l:item in l:file_list
         if bufnr(l:item.file) is a:buffer
             return ale#c#ParseCFlags(a:dir, l:item.command)
         endif
@@ -197,7 +214,10 @@ function! ale#c#ParseCompileCommandsFlags(buffer, dir, json_list) abort
     " Look for any file in the same directory if we can't find an exact match.
     let l:dir = ale#path#Simplify(expand('#' . a:buffer . ':p:h'))
 
-    for l:item in a:json_list
+    let l:dirbasename = tolower(expand('#' . a:buffer . ':p:h:t'))
+    let l:dir_list = get(a:dir_lookup, l:dirbasename, [])
+
+    for l:item in l:dir_list
         if ale#path#Simplify(fnamemodify(l:item.file, ':h')) is? l:dir
             return ale#c#ParseCFlags(a:dir, l:item.command)
         endif
@@ -208,9 +228,11 @@ endfunction
 
 function! ale#c#FlagsFromCompileCommands(buffer, compile_commands_file) abort
     let l:dir = ale#path#Dirname(a:compile_commands_file)
-    let l:json_list = s:GetListFromCompileCommandsFile(a:compile_commands_file)
+    let l:lookups = s:GetLookupFromCompileCommandsFile(a:compile_commands_file)
+    let l:file_lookup = l:lookups[0]
+    let l:dir_lookup = l:lookups[1]
 
-    return ale#c#ParseCompileCommandsFlags(a:buffer, l:dir, l:json_list)
+    return ale#c#ParseCompileCommandsFlags(a:buffer, l:dir, l:file_lookup, l:dir_lookup)
 endfunction
 
 function! ale#c#GetCFlags(buffer, output) abort
diff --git a/test/compile_database_perf/test.sh b/test/compile_database_perf/test.sh
new file mode 100755
index 00000000..15a2b442
--- /dev/null
+++ b/test/compile_database_perf/test.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# Generate source files for ALE to read. They don't have to be very long, the delay is in reading compile_commands, not actually running tests
+mkdir -p gen_src
+for i in {1..400}; do echo "const char *GeneratedFunc${i}() { return \"Word ${i}\"; }" > gen_src/source${i}.cpp; done
+
+# Create the compile_commands database
+echo "[ {" > compile_commands.json
+
+for i in {1..399}; do 
+  {
+    echo "\"command\": \"clang++ -c $(pwd)/gen_src/source${i}.cpp -o $(pwd)/build/obj/Debug/source${i}.o -MF $(pwd)/build/obj/Debug/source${i}.d -MMD -MP\","
+    echo "\"directory\": \"$(pwd)/build\","
+    echo "\"file\": \"$(pwd)/gen_src/source${i}.cpp\""
+    echo "}, {"
+  } >> compile_commands.json
+done
+
+{
+  echo "\"command\": \"clang++ -c $(pwd)/gen_src/source400.cpp -o $(pwd)/build/obj/Debug/source400.o -MF $(pwd)/build/obj/Debug/source400.d -MMD -MP\","
+  echo "\"directory\": \"$(pwd)/build\","
+  echo "\"file\": \"$(pwd)/gen_src/source400.cpp\""
+  echo "} ]"
+} >> compile_commands.json
+
+# Start up vim and switch back and forth between files -- at least one of the files must be near the bottom of compile_commands.json
+time vim -c "for i in range(0,20) | edit gen_src/source10.cpp | edit gen_src/source400.cpp | endfor" \
+  -c "noautocmd qa!" \
+  `find . | grep "source..\.cpp"`
diff --git a/test/test_c_flag_parsing.vader b/test/test_c_flag_parsing.vader
index d3cb2b51..4c23c711 100644
--- a/test/test_c_flag_parsing.vader
+++ b/test/test_c_flag_parsing.vader
@@ -161,14 +161,14 @@ Execute(FlagsFromCompileCommands should tolerate empty values):
   AssertEqual '', ale#c#FlagsFromCompileCommands(bufnr(''), '')
 
 Execute(ParseCompileCommandsFlags should tolerate empty values):
-  AssertEqual '', ale#c#ParseCompileCommandsFlags(bufnr(''), '', [])
+  AssertEqual '', ale#c#ParseCompileCommandsFlags(bufnr(''), '', {}, {})
 
 Execute(ParseCompileCommandsFlags should parse some basic flags):
   noautocmd execute 'file! ' . fnameescape(ale#path#Simplify('/foo/bar/xmms2-mpris/src/xmms2-mpris.c'))
 
   AssertEqual
   \ '-I' . ale#path#Simplify('/usr/include/xmms2'),
-  \ ale#c#ParseCompileCommandsFlags(bufnr(''), ale#path#Simplify('/foo/bar/xmms2-mpris'), [
+  \ ale#c#ParseCompileCommandsFlags(bufnr(''), ale#path#Simplify('/foo/bar/xmms2-mpris'), { "xmms2-mpris.c": [
   \   {
   \     'directory': ale#path#Simplify('/foo/bar/xmms2-mpris'),
   \     'command': '/usr/bin/cc  -I' . ale#path#Simplify('/usr/include/xmms2')
@@ -176,7 +176,22 @@ Execute(ParseCompileCommandsFlags should parse some basic flags):
   \       . '   -c ' . ale#path#Simplify('/foo/bar/xmms2-mpris/src/xmms2-mpris.c'),
   \     'file': ale#path#Simplify('/foo/bar/xmms2-mpris/src/xmms2-mpris.c'),
   \   },
-  \ ])
+  \ ] }, {})
+
+Execute(ParseCompileCommandsFlags should fall back to files in the same directory):
+  noautocmd execute 'file! ' . fnameescape(ale#path#Simplify('/foo/bar/xmms2-mpris/src/xmms2-mpris.c'))
+
+  AssertEqual
+  \ '-I' . ale#path#Simplify('/usr/include/xmms2'),
+  \ ale#c#ParseCompileCommandsFlags(bufnr(''), ale#path#Simplify('/foo/bar/xmms2-mpris'), {}, { "src": [
+  \   {
+  \     'directory': ale#path#Simplify('/foo/bar/xmms2-mpris'),
+  \     'command': '/usr/bin/cc  -I' . ale#path#Simplify('/usr/include/xmms2')
+  \       . '    -o CMakeFiles/xmms2-mpris.dir/src/xmms2-mpris.c.o'
+  \       . '   -c ' . ale#path#Simplify('/foo/bar/xmms2-mpris/src/xmms2-mpris.c'),
+  \     'file': ale#path#Simplify((has('win32') ? 'C:' : '') . '/foo/bar/xmms2-mpris/src/xmms2-other.c'),
+  \   },
+  \ ] })
 
 Execute(ParseCFlags should not merge flags):
   AssertEqual