Google Developers Blog: Gmail for Mobile HTML5 Series: Suggestions for Better Performance

Gmail for Mobile HTML5 Series: Suggestions for Better Performance

Wednesday, June 10, 2009

On April 7th, Google launched a new version of Gmail for mobile for iPhone and Android-powered devices. We shared the behind-the-scenes story through this blog and decided to share more of our learnings in a brief series of follow-up blog posts. This week, I'll talk about a few small things you can do to improve performance of your HTML5-based applications. Our focus here will be on performance bottlenecks related to the database and AppCache.Optimizing Database PerformanceCreating and deleting tables is slow!Smart versioning and backwards compatible schema changes (whenever possible).Queries are slow!Defer and/or combine queries.SELECT Author, COUNT(*) as NumArticles
FROM Magazines
GROUP BY Author
ORDER BY NumArticles;

SELECT Author, COUNT(*) as NumBooks
FROM Books
GROUP BY Author
ORDER BY NumBooks;

SELECT Author, NumPublications, PubType
FROM (
  SELECT Author, COUNT(*) as NumPublications, 'Magazine' as PubType, 0 as SortIndex
  FROM Magazines
  GROUP BY Author
  UNION
  SELECT Author, COUNT(*) as NumPublications, 'Book' as PubType, 1 as SortIndex
  FROM Books
  GROUP BY Author
)
ORDER BY SortIndex, NumPublications;

Multiple updates is slow!Use Triggers whenever possible.

CREATE TRIGGER IF NOT EXISTS RemoveAuthor
AFTER DELETE ON Books
BEGIN
  DELETE FROM Authors
  WHERE Author NOT IN
    (SELECT Author
     FROM Books);
END;

Optimizing AppCache PerformanceLogging in is slow!AppCache reloading causes my app to be slow!List as few URLs in the manifest as possible.series of posts