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copied!<p>The vast majority of the apps on the platform (contacts, Email, Gmail, calendar, etc.) do not do this. Some of these have extremely complicated database schemas with potentially a large amount of data and do not need to do this. What you are proposing to do is going to cause <em>huge</em> pain for you, with no clear gain.</p> <p>You should first focus on designing your database and schema to be able to do efficient queries. There are two main reasons I can think of for database access to be slow:</p> <ul> <li>You have really complicated data schemas.</li> <li>You have a very large amount of data.</li> </ul> <p>If you are going to have a lot of data, you can't afford to keep it all in memory anyway, so this is a dead end. If you have complicated structures, you would benefit in either case with optimizing them to improve performance. In both cases, your database schema is going to be key to good performance.</p> <p>Actually optimizing the schema can be a bit a of a black art (and I am no expert on it), but some things to look out for are correctly creating indices on rows you will query, designing joins so they will take efficient paths, etc. I am sure there are lots of people who can help you with this area.</p> <p>You could also try looking at the source of some of the platform's databases to get some ideas of how to design for good performance. For example the Contacts database (especially starting with 2.0) is extremely complicated and has a lot of optimizations to provide good performance on relatively large data and extensible data sets with lots of different kinds of queries.</p> <p>Update:</p> <p>Here's a good illustration of how important database optimization is. In Android's media provider database, a newer version of the platform changed the schema significantly to add some new features. The upgrade code to modify an existing media database to the new schema could take 8 minutes or more to execute.</p> <p>An engineer made an optimization that reduced the upgrade time of a real test database from 8 minutes to 8 seconds. A 60x performance improvement.</p> <p>What was this optimization?</p> <p>It was to create a temporary index, at the point of upgrade, on an important column used in the upgrade operations. (And then delete it when done.) So this 60x performance improvement comes even though it also includes the time needed to build an index on one of the columns used during upgrading.</p> <p>SQLite is one of those things where if you know what you are doing it can be remarkably efficient. And if you don't take care in how you use it, you can end up with wretched performance. It is a safe bet, though, if you are having performance issues with it that you can fix them by improving how you are using SQLite.</p>

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