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List:       sqlite-users
Subject:    Re: [sqlite] View - What happens internally
From:       Dan <danielk1977 () gmail ! com>
Date:       2009-02-28 14:37:45
Message-ID: A77E23B7-9671-4D3E-A346-D58FF6C80E0D () gmail ! com
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On Feb 28, 2009, at 8:44 PM, Lloyd wrote:

>
> Hi,
>
> When we create a view what happens internally in sqlite? Does it  
> select
> all the data from the table and then "insert" it in to the view? or  
> would
> the records in the view keep references to records in main table?  
> just to
> know whether creating more views on a big in-memory database would  
> require
> more memory.

A view in SQLite is just a SELECT statement that is saved in the  
database
schema. If you do:

   CREATE VIEW v1 AS SELECT * FROM t1;
   SELECT * FROM v1;

The SQL compiler (the thing that runs when you call  
sqlite3_prepare_v2())
converts the select statement to "SELECT * FROM (SELECT * FROM t1)"
before compiling a prepared statement to implement the query.

So adding a view doesn't require a huge amount of extra memory.

Dan.


>
>
> Thanks,
>   Lloyd
>
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