要解决这些问题，可以删除无关的索引，添加一个新的索引，或者在某些表中周期性地清除大量过期的数据。

To solve these problems, drop the extraneous index, add a new index, or periodically clean out the large volume of obsolete data in some tables.

youdao

理想情况下，索引提供了足够多的信息，可以只读入所需要的行，但是有时候查询(设计不佳或数据本性使然)需要读取表中大量数据。

Ideally, the indexes provide enough information to read in only the needed rows, but sometimes queries (through poor design or the nature of the data) require large chunks of the table to be read.

youdao

此处的“大量”可能意味着10%到20%的表和索引数据都受到了影响。

"Extensive" in this case may mean that 10 to 20 percent of the table and index data has been affected.

youdao