diff --git a/scripts/symbols/clear_project_symbols.php b/scripts/symbols/clear_project_symbols.php
new file mode 100755
index 0000000000..cd1df72f2e
--- /dev/null
+++ b/scripts/symbols/clear_project_symbols.php
@@ -0,0 +1,48 @@
+#!/usr/bin/env php
+<?php
+
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+$root = dirname(dirname(dirname(__FILE__)));
+require_once $root.'/scripts/__init_script__.php';
+
+$project = id(new PhabricatorRepositoryArcanistProject())->loadOneWhere(
+  'name = %s', $argv[1]);
+if (!$project) {
+  throw new Exception('No such arcanist project.');
+}
+
+$input = file_get_contents('php://stdin');
+$normalized = array();
+foreach (explode("\n", trim($input)) as $path) {
+  // emulate the behavior of the symbol generation scripts
+  $normalized[] = '/'.ltrim($path, './');
+}
+$paths = PhabricatorRepositoryCommitChangeParserWorker::lookupOrCreatePaths(
+  $normalized);
+
+$symbol = new PhabricatorRepositorySymbol();
+$conn_w = $symbol->establishConnection('w');
+
+foreach (array_chunk(array_values($paths), 128) as $chunk) {
+  queryfx(
+    $conn_w,
+    'DELETE FROM %T WHERE arcanistProjectID = %d AND pathID IN (%Ld)',
+    $symbol->getTableName(),
+    $project->getID(),
+    $chunk);
+}
diff --git a/scripts/symbols/import_project_symbols.php b/scripts/symbols/import_project_symbols.php
index 4ff2a3f2cd..b09fc6f377 100755
--- a/scripts/symbols/import_project_symbols.php
+++ b/scripts/symbols/import_project_symbols.php
@@ -1,172 +1,179 @@
 #!/usr/bin/env php
 <?php
 
 /*
  * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 $root = dirname(dirname(dirname(__FILE__)));
 require_once $root.'/scripts/__init_script__.php';
 
 $args = new PhutilArgumentParser($argv);
 $args->setSynopsis(<<<EOSYNOPSIS
 **import_project_symbols.php** [__options__] __project_name__ < symbols
 
   Import project symbols (symbols are read from stdin).
 EOSYNOPSIS
   );
 $args->parseStandardArguments();
 $args->parse(
   array(
+    array(
+      'name'      => 'no-purge',
+      'help'      => 'Do not clear all symbols for this project before '.
+                     'uploading new symbols. Useful for incremental updating.',
+    ),
     array(
       'name'      => 'more',
       'wildcard'  => true,
     ),
   ));
 
 $more = $args->getArg('more');
 if (count($more) !== 1) {
   $args->printHelpAndExit();
 }
 
 $project_name = head($more);
 $project = id(new PhabricatorRepositoryArcanistProject())->loadOneWhere(
   'name = %s',
   $project_name);
 
 if (!$project) {
   // TODO: Provide a less silly way to do this explicitly, or just do it right
   // here.
   echo "Project '{$project_name}' is unknown. Upload a diff to implicitly ".
        "create it.\n";
   exit(1);
 }
 
 echo "Parsing input from stdin...\n";
 $input = file_get_contents('php://stdin');
 $input = trim($input);
 $input = explode("\n", $input);
 
 $symbols = array();
 foreach ($input as $key => $line) {
   $line_no = $key + 1;
   $matches = null;
   $ok = preg_match(
     '/^((?P<context>[^ ]+)? )?(?P<name>[^ ]+) (?P<type>[^ ]+) '.
     '(?P<lang>[^ ]+) (?P<line>\d+) (?P<path>.*)$/',
     $line,
     $matches);
   if (!$ok) {
     throw new Exception(
       "Line #{$line_no} of input is invalid. Expected five or six ".
       "space-delimited fields: maybe symbol context, symbol name, symbol ".
       "type, symbol language, line number, path. ".
       "For example:\n\n".
       "idx function php 13 /path/to/some/file.php\n\n".
       "Actual line was:\n\n".
       "{$line}");
   }
   if (empty($matches['context'])) {
     $matches['context'] = '';
   }
   $context     = $matches['context'];
   $name        = $matches['name'];
   $type        = $matches['type'];
   $lang        = $matches['lang'];
   $line_number = $matches['line'];
   $path        = $matches['path'];
 
   if (strlen($context) > 128) {
     throw new Exception(
       "Symbol context '{$context}' defined on line #{$line_no} is too long, ".
       "maximum symbol context length is 128 characters.");
   }
 
   if (strlen($name) > 128) {
     throw new Exception(
       "Symbol name '{$name}' defined on line #{$line_no} is too long, maximum ".
       "symbol name length is 128 characters.");
   }
 
   if (strlen($type) > 12) {
     throw new Exception(
       "Symbol type '{$type}' defined on line #{$line_no} is too long, maximum ".
       "symbol type length is 12 characters.");
   }
 
   if (strlen($lang) > 32) {
     throw new Exception(
       "Symbol language '{$lang}' defined on line #{$line_no} is too long, ".
       "maximum symbol language length is 32 characters.");
   }
 
   if (!strlen($path) || $path[0] != 0) {
     throw new Exception(
       "Path '{$path}' defined on line #{$line_no} is invalid. Paths should be ".
       "begin with '/' and specify a path from the root of the project, like ".
       "'/src/utils/utils.php'.");
   }
 
   $symbols[] = array(
     'ctxt' => $context,
     'name' => $name,
     'type' => $type,
     'lang' => $lang,
     'line' => $line_number,
     'path' => $path,
   );
 }
 
 echo "Looking up path IDs...\n";
 $path_map = PhabricatorRepositoryCommitChangeParserWorker::lookupOrCreatePaths(
   ipull($symbols, 'path'));
 
 $symbol = new PhabricatorRepositorySymbol();
 $conn_w = $symbol->establishConnection('w');
 
 echo "Preparing queries...\n";
 $sql = array();
 foreach ($symbols as $dict) {
   $sql[] = qsprintf(
     $conn_w,
     '(%d, %s, %s, %s, %s, %d, %d)',
     $project->getID(),
     $dict['ctxt'],
     $dict['name'],
     $dict['type'],
     $dict['lang'],
     $dict['line'],
     $path_map[$dict['path']]);
 }
 
-echo "Purging old symbols...\n";
-queryfx(
-  $conn_w,
-  'DELETE FROM %T WHERE arcanistProjectID = %d',
-  $symbol->getTableName(),
-  $project->getID());
+if (!$args->getArg('no-purge')) {
+  echo "Purging old symbols...\n";
+  queryfx(
+    $conn_w,
+    'DELETE FROM %T WHERE arcanistProjectID = %d',
+    $symbol->getTableName(),
+    $project->getID());
+}
 
 echo "Loading ".number_format(count($sql))." symbols...\n";
 foreach (array_chunk($sql, 128) as $chunk) {
   queryfx(
     $conn_w,
     'INSERT INTO %T
       (arcanistProjectID, symbolContext, symbolName, symbolType,
         symbolLanguage, lineNumber, pathID) VALUES %Q',
     $symbol->getTableName(),
     implode(', ', $chunk));
 }
 
 echo "Done.\n";