Ever wonder how many rows you store per page? Me too. So here’s the query I use to investigate this:
Select object_name(i.object_id) As 'tableName' , i.name As 'indexName' , i.type_desc , Max(p.partition_number) As 'partitions' , Sum(p.rows) As 'rows' , Sum(au.data_pages) As 'dataPages' , Sum(p.rows) / Sum(au.data_pages) As 'rowsPerPage' From sys.indexes As i Join sys.partitions As p On i.object_id = p.object_id And i.index_id = p.index_id Join sys.allocation_units As au On p.hobt_id = au.container_id Where object_name(i.object_id) Not Like 'sys%' And au.type_desc = 'IN_ROW_DATA' Group By object_name(i.object_id) , i.name , i.type_desc Having Sum(au.data_pages) > 100 Order By rowsPerPage;
What does this tell you? Well, the more rows you can fit on a page, the less IO you need to consume to retrieve those rows. It’s also a good way to improve your buffer cache hit ratio (i.e. retrieve data from memory instead of disk, which is more efficient). So take a good look at those first few rows… do you have a small number of [rowsPerPage] but a large number of [rows]? If so, it may be time to look at re-designing your tables.
Michelle Ufford (aka SQLFool)