l) 其他执行信息 (1)sort 算子,会显示排序信息 Sort Method代表排序的方法,包括quicksort(快排)和disksort(外排)。快排即内存够用时,所有的排序操作均在内存中完成,外排说明当前可用内存不足,需要下盘。 (2)hashjoin算子 Buckets:代表hash表中实际使用的桶的个数 Batches:代表hashjoin中实际分块的数量。如果Batch...
这个filesort是说, MySQL要多做一次额外的排序, 确切的说是快速排序(Quicksort). 先初步了解下Quicksort排序的概念(From Wikipedia). Quicksort is a divide and conquer algorithm. Quicksort first divides a large array into two smaller sub-arrays: the low elements and the high elements. Quicksort can ...
The algorithm isn't simply returning the values that account for the biggest amount of the change. For example, if most (98%) sales came from the USA, then it would commonly be the case that most of the increase was also in the USA. Yet unless the USA or other countries/regions had...
In this example there are 2 filter steps. The first is effectively like a NL except that it stops when it gets something that it doesn't like (i.e. a bounded NL). This is there because of the not in. The second is filtering out the min value: SQL> explain plan for select * fro...
The longest match number string dial-peer algorithm finds the dial-peer with the most numbers in a sequence that exactly match a sequence of numbers in a number string. This concept is clarified in the subsequent scenario. Scenario: Eligible dial-peers have been configured with t...
1. What is the difference between the worse case and the best case running time of a merge sort? 2. True or false? Let Ai and Ai+1 be the ith largest and the (i+1) largest elements in A. Any algorithm E...
Seems to me, it simply means "has that playing position (i.e. the current state) been reached by pitting 'the algorithm' vs. any particular genuine chess-engine". (Or otherwise. The alternative, presumably, that it was a 'hand-crafted' response on Randall's part... Or possibly a volu...
SortSelected rows were sorted using a sort algorithm. Union MergeThe results of multiple subselects were merged or combined into a single result. Subquery MergeThe results of multiple subselects were merged or combined into a single result. ...
The "crypto nerd" (short for cryptography in this case, not cryptocurrency, which was only invented a few months before this comic) would be concerned with strongly encrypting data on their personal machine. This would conceivably come in handy when "villains" attempt to steal information on his...
with 48 commentsFrom Stack Overflow: Can anyone give me a good example of when CROSS APPLY makes a difference in those cases where INNER JOIN will work as well? This is of course SQL Server. A quick reminder on the terms. INNER JOIN is the most used construct in SQL: it joins two ...