Covered indexes enhance performance when all fields requested by a query are contained within the covered index because there is no need to pull up the full document record.

Covered索引在查询所请求的全部字段都包含在Covered索引中时能提升性能，因为不再需要取出完整的文档记录。

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Yet the work is more than simply a record or document as Wicks explains.

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Prosecutor Ken Karas read the document into the court record Tuesday morning.

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Others have noted that authorities in Jiangsu didn't publicize the cases there until after a hospital record purporting to document a local H7N9 infection was posted on Sina Weibo.

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