Let SQL Server Tell You Which Indexes to Rebuild

5 בינואר 2009

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When index fragmentation becomes too high, indexes will be very inefficient. Other than planning a good index design, you should rebuild / reorganize your indexes every once in a while.

SELECT 'ALTER INDEX [' + ix.name + '] ON [' + s.name + '].[' + t.name + '] ' +
       CASE WHEN ps.avg_fragmentation_in_percent > 40 THEN 'REBUILD' ELSE 'REORGANIZE' END +
       CASE WHEN pc.partition_count > 1 THEN ' PARTITION = ' + cast(ps.partition_number as nvarchar(max)) ELSE '' END
FROM   sys.indexes AS ix INNER JOIN sys.tables t
           ON t.object_id = ix.object_id
       INNER JOIN sys.schemas s
           ON t.schema_id = s.schema_id
       INNER JOIN (SELECT object_id, index_id, avg_fragmentation_in_percent, partition_number
                   FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL, NULL, NULL)) ps
           ON t.object_id = ps.object_id AND ix.index_id = ps.index_id
       INNER JOIN (SELECT object_id, index_id, COUNT(DISTINCT partition_number) AS partition_count
                   FROM sys.partitions
                   GROUP BY object_id, index_id) pc
           ON t.object_id = pc.object_id AND ix.index_id = pc.index_id
WHERE  ps.avg_fragmentation_in_percent > 10 AND
       ix.name IS NOT NULL

The above query will give you a list of recommended index rebuild / reorganize statements for your database, according Pinal Dave’s 10-40 rule, although you are welcome to tweak it to your liking. It supports non-partitioned as well as partitioned indexes. If you want a more intense check for fragmentation, change the last NULL in the dm_db_index_physical_stats call to 'SAMPLED' or even 'DETAILED' (include quotes).

It’s a handy little tool for database administrators and saves a lot of the hassle of monitoring index fragmentation.

Update: Added multi-schema support as suggested by MJ12 and another check for null index names.

[Cross-Posted from Omer van Kloeten's .NET Zen, my English language weblog]

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