On 06/28/2012 02:16 PM, David E. Wheeler wrote:

Very interesting design document for SQLite 4:


I'm particularly intrigued by "covering indexes". For example:

     CREATE INDEX cover1 ON table1(a,b) COVERING(c,d);

This allows the following query to do an index-only scan:

     SELECT c, d FROM table1 WHERE a=? AND b=?;

Now that we have index-only scans in 9.2, I'm wondering if it would make sense 
to add covering index support, too, where additional, unindexed columns are 
stored alongside indexed columns.

And I wonder if it would work well with expressions, too?


This is analogous to SQL Server's "include" :

|ON my_table (status)|
|INCLUDE (someColumn, otherColumn)|

Which is useful, but bloats the index.

Andreas Joseph Krogh<andr...@officenet.no>  - mob: +47 909 56 963
Senior Software Developer / CEO - OfficeNet AS - http://www.officenet.no
Public key: http://home.officenet.no/~andreak/public_key.asc

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