filesort
Short Description
The using_filesort node is seen where MySQL is performing an extra pass in order to sort the data
Detailed Description​
The using_filesort
node is seen where MySQL is performing an extra pass in order to sort the data. This typically happens where no supporting index can be used to satisfy the query.
Sorting is performed in memory so long as the sorted data fits within sort_buffer_size. If this is exceeded, the sort will spill to disk and performance will suffer.
JSON property:Â using_filesort
Additional Links​
- MySQL Documentation - Order By Optimization - Use of filesort
- MySQL Documentation - Explain Output
- MySQL Documentation - Explain
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