Query Parsing and optimization needs memory. This is usually small to be ignored but certain queries can have very large memory requrement for this step, especially specially crafted ones.

• 解析查询和优化都需要内存。这些内存通常比较小,可以忽略,不过如果是某些查询在这个步骤中则需要大量内存,尤其是那些设计的比较特别的查询。