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...
为了更好的理解EXPLAIN,rows参数也是一个很好的参考,以下来自官网对rows的解释: Therowscolumn indicates the number of rows MySQL believes it must examine to execute the query. ForInnoDBtables, this number is an estimate, and may not always be exact. 这个字段表示MySQL认为执行查询必须检查的行数。 对...
print(quicksort([10, 5, 2, 3])) 再回来说filesort, 在MySQL中有the Original, Modified和In-Memory filesort Algorithm 3种实现. The Original filesort Algorithm 1. 扫描或根据WHERE条件, 获取所有记录. 2. 把每条记录的sort key和row ID, 即<sort_key, rowid>, 放入sort buffer中. 若sort buffer满...
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...
the library cache based upon a hashed representation of that query. When looking for a statement in the library cache, we first apply a hashing algorithm to the statement and then we look for this hash value in the library cache. This access path will be used until the query is reparsed...
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...
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. ...
SEME might be large, at least in part, because people generally trust computer output more than they trust content in which the human hand is evident (Bogert et al., 2021; Logg et al., 2019). Most people have no idea how computers work or what an algorithm is; as a result,...
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...