索引维护 [英] Index Maintenance

问题描述

什么是索引维护，我如何做？我需要多长时间做一次？
有什么好处？
这与一个经常修改的事务表有关;所有DML操作都将在该表上运行。

What is Index Maintenance and how do I do it? How frequently do I have to do it? What are the benefits? This is related to a transaction table which is subject to frequently modifications; all DML operations will be run on that table.

推荐答案

我继承Jonathan所说的一切 - 除了索引维护的频率。

I second everything that Jonathan said - except for the frequency of index maintenance.

好吧，如果你碰巧有一个设计不佳的索引（例如GUID密钥上的聚集索引），你实际上可能需要至少每天晚上做一次 - 或者甚至在白天。

Well, if you happen to have a poorly designed index (such as a clustered index on a GUID key), you might actually need to do it at least every night - or even during the day, too.

作为一般的经验法则：如果你的索引碎片低于5％，一切都很好。如果您的碎片在5％和约5％之间。 30％，您应该进行索引重组：

As a general rule of thumb: if your index fragmentation is below 5%, all is fine. If you have fragmentation between 5% and approx. 30%, you should do an index reorganization:

ALTER INDEX (your index name) ON (your table name) REORGANIZE

如果您的索引的索引碎片大于30％，则需要完全重建：

If your index has index fragmentation of more than 30%, you need to rebuild it completely:

ALTER INDEX (your index name) ON (your table name) REBUILD

重建索引可能会造成中断 - 尝试在非工作时间执行，例如

Rebuilding an index can be disruptive - try to do it at off-hours, e.g. during the night.

为了确定索引碎片，您可以使用此DMV查询：

In order to determine index fragmentation, you can use this DMV query:

SELECT 
    t.NAME 'Table name',
    i.NAME 'Index name',
    ips.index_type_desc,
    ips.alloc_unit_type_desc,
    ips.index_depth,
    ips.index_level,
    ips.avg_fragmentation_in_percent,
    ips.fragment_count,
    ips.avg_fragment_size_in_pages,
    ips.page_count,
    ips.avg_page_space_used_in_percent,
    ips.record_count,
    ips.ghost_record_count,
    ips.Version_ghost_record_count,
    ips.min_record_size_in_bytes,
    ips.max_record_size_in_bytes,
    ips.avg_record_size_in_bytes,
    ips.forwarded_record_count
FROM 
    sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'DETAILED') ips
INNER JOIN  
    sys.tables t ON ips.OBJECT_ID = t.Object_ID
INNER JOIN  
    sys.indexes i ON ips.index_id = i.index_id AND ips.OBJECT_ID = i.object_id
WHERE
    AVG_FRAGMENTATION_IN_PERCENT > 0.0
ORDER BY
    AVG_FRAGMENTATION_IN_PERCENT, fragment_count

Michelle Ufford有一个很好的自动< a href =http://sqlfool.com/2009/03/automated-index-defrag-script/ =noreferrer> index defrag script - 强烈推荐！或者，您应该考虑设置 SQL Server维护计划，该计划可以运行每天晚上清理您的指数。

Michelle Ufford has a great automatic index defrag script - highly recommended! Or then you should look into setting up SQL Server maintenance plans which can run e.g. every night and clean up your indices.

Marc

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