IO Statistics now available for queries that use Columnstore indexes


Prior to SQL Server 2014 Service Pack 1, if you turned on STATISTICS IO for queries that touch Columnstore index, it would always report 0 as seen in the simple example below:

 

CREATE
TABLE t
(c INT)

GO

INSERT
INTO t VALUES (1)

GO

CREATE
CLUSTERED
COLUMNSTORE
INDEX cci ON t

GO

SET
STATISTICS
IO
ON

GO

SELECT
*
FROM t

 

Table ‘t’. Scan count 1, logical reads 6, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 

This has been corrected in SQL Server 2014 SP1, where you can now see the columnstore statistics under lob reads. In addition, you will also see segment level statistics

Table ‘t’. Scan count 1, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 6, lob physical reads 0, lob read-ahead reads 0.

Table ‘t’. Segment reads 1, segment skipped 0.


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