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MySQL 5.7 Reference Manual
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21.2.7.7 Limitations Relating to Performance in NDB Cluster

The following performance issues are specific to or especially pronounced in NDB Cluster:

  • Range scans.  There are query performance issues due to sequential access to theNDB storage engine; it is also relatively more expensive to do many range scans than it is with eitherMyISAM orInnoDB.

  • Reliability of Records in range.  TheRecords in range statistic is available but is not completely tested or officially supported. This may result in nonoptimal query plans in some cases. If necessary, you can employUSE INDEX orFORCE INDEX to alter the execution plan. SeeSection 8.9.4, “Index Hints”, for more information on how to do this.

  • Unique hash indexes.  Unique hash indexes created withUSING HASH cannot be used for accessing a table ifNULL is given as part of the key.