后一种情况比较简单,所执行的是快速散列查找。
可以使用一个散列来进一步优化这个循环,但是坦白讲我并不认为这有多重要,除非用户要在无数的唱片中查找。
I could have used a hash to optimize this loop further, but frankly I don't think it would have made a difference at all unless the user was finding hundreds of thousands of albums.
如果查找成功,就检索可以作为散列引用回给调用者的那一行。
If this succeeds, that row is retrieved as a hash reference that can be returned to the caller.
该连接的执行过程包括扫描散列连接中的内表CUSTOMERS,并通过散列连接列的值生成一个查找表。
The join is performed by scanning the inner table of the hash join, CUSTOMERS, and generating a lookup table by hashing the join column values.
然后,它使用SHIP操作符读外表BAD_CREDIT,散列连接列的值,并检查为内表生成的查找表。
IT then reads from the outer table BAD_CREDIT using the SHIP operator, hashing the join column values, and checking in the lookup table generated for the inner table.
LinkedIn在其Hadoop管道上构建了一个索引结构:这会产生几个TB的查找结构,该结构完美地使用了散列(每个键只需要2.5个位)。
LinkedIn builds an index structure in their Hadoop pipeline - this produces a multi-TB lookup structure that USES perfect hashing (requiring only 2.5 bits per key).
顾名思义,散列部分用散列算法存储及查找它的键。
As the name implies, the hash part USES a hash algorithm to store and find its keys.
顾名思义,散列部分用散列算法存储及查找它的键。
As the name implies, the hash part USES a hash algorithm to store and find its keys.
应用推荐