Misc. cleanup found while mucking with search engines code:

chrome/browser/webdata/keyword_table.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/webdata/keyword_table.h"
 
 #include <set>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
@@ skipping 228 matching lines @@
   }
 
   return true;
 }
 
 bool KeywordTable::AddKeyword(const TemplateURLData& data) {
   DCHECK(data.id);
   std::string query("INSERT INTO keywords (" + GetKeywordColumns() + ") "
                     "VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,"
                     "        ?)");
-  sql::Statement s(db_->GetUniqueStatement(query.c_str()));
+  sql::Statement s(db_->GetCachedStatement(SQL_FROM_HERE, query.c_str()));

[Scott Hess - ex-Googler, 2014/03/31 18:09:08]

I hate constructed queries with a vengence.  That said, AFAICT,
GetKeywordColumns() will be static for a given run of Chrome, so I think this
works.

In changing these from unique to cached, do you actually expect them to be
called frequently enough that retaining the prepared statement will win
anything?  These look like pretty simple statements.  I'd say if they aren't
expected to be called a few times every time Chromium is executed, they might
not be worthwhile to cache.

[Peter Kasting, 2014/03/31 19:53:56]

They may not be executed multiple times on every Chrome invocation, but when
they _are_ executed, they may be executed dozens or even hundreds of times. 
This is the case for e.g. syncing an existing set of search engines to a new
profile/installation.

[Scott Hess - ex-Googler, 2014/03/31 23:52:08]

OK.  I sometimes/often feel like we need a more adaptive statement cache which
actually works like a _cache_.

[Peter Kasting, 2014/04/01 00:18:56]

Yeah, it would be nice if there was a simple LRU cache for each table, or
something like that, and the caller didn't have to make any distinction between
statements, it was all just done automatically.

   BindURLToStatement(data, &s, 0, 1);
 
   return s.Run();
 }
 
 bool KeywordTable::RemoveKeyword(TemplateURLID id) {
   DCHECK(id);
-  sql::Statement s(
-      db_->GetUniqueStatement("DELETE FROM keywords WHERE id = ?"));
+  sql::Statement s(db_->GetCachedStatement(
+      SQL_FROM_HERE, "DELETE FROM keywords WHERE id = ?"));
   s.BindInt64(0, id);
 
   return s.Run();
 }
 
 bool KeywordTable::GetKeywords(Keywords* keywords) {
   std::string query("SELECT " + GetKeywordColumns() +
                     " FROM keywords ORDER BY id ASC");
   sql::Statement s(db_->GetUniqueStatement(query.c_str()));
 
   std::set<TemplateURLID> bad_entries;
   while (s.Step()) {
     keywords->push_back(TemplateURLData());
     if (!GetKeywordDataFromStatement(s, &keywords->back())) {
       bad_entries.insert(s.ColumnInt64(0));
       keywords->pop_back();
     }
   }
   bool succeeded = s.Succeeded();
   for (std::set<TemplateURLID>::const_iterator i(bad_entries.begin());
        i != bad_entries.end(); ++i)
     succeeded &= RemoveKeyword(*i);
   return succeeded;
 }
 
 bool KeywordTable::UpdateKeyword(const TemplateURLData& data) {
   DCHECK(data.id);
-  sql::Statement s(db_->GetUniqueStatement("UPDATE keywords SET short_name=?, "
-      "keyword=?, favicon_url=?, url=?, safe_for_autoreplace=?, "
-      "originating_url=?, date_created=?, usage_count=?, input_encodings=?, "
-      "show_in_default_list=?, suggest_url=?, prepopulate_id=?, "
-      "created_by_policy=?, instant_url=?, last_modified=?, sync_guid=?, "
-      "alternate_urls=?, search_terms_replacement_key=?, image_url=?,"
-      "search_url_post_params=?, suggest_url_post_params=?, "
-      "instant_url_post_params=?, image_url_post_params=?, new_tab_url=? "
-      "WHERE id=?"));
+  sql::Statement s(db_->GetCachedStatement(
+      SQL_FROM_HERE,
+      "UPDATE keywords SET short_name=?, keyword=?, favicon_url=?, url=?, "
+      "safe_for_autoreplace=?, originating_url=?, date_created=?, "
+      "usage_count=?, input_encodings=?, show_in_default_list=?, "
+      "suggest_url=?, prepopulate_id=?, created_by_policy=?, instant_url=?, "
+      "last_modified=?, sync_guid=?, alternate_urls=?, "
+      "search_terms_replacement_key=?, image_url=?, search_url_post_params=?, "
+      "suggest_url_post_params=?, instant_url_post_params=?, "
+      "image_url_post_params=?, new_tab_url=? WHERE id=?"));
   BindURLToStatement(data, &s, 24, 0);  // "24" binds id() as the last item.
 
   return s.Run();
 }
 
 bool KeywordTable::SetDefaultSearchProviderID(int64 id) {
   return meta_table_->SetValue(kDefaultSearchProviderKey, id);
 }
 
 int64 KeywordTable::GetDefaultSearchProviderID() {
@@ skipping 369 matching lines @@
     }
   }
 
   // Replace the old table with the new one.
   sql = "DROP TABLE " + name;
   if (!db_->Execute(sql.c_str()))
     return false;
   sql = "ALTER TABLE keywords_temp RENAME TO " + name;
   return db_->Execute(sql.c_str());
 }