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bdj625145
Apr 20, 2022
In Welcome to the Forum
In this blog, we will discuss the connections on the map side and its advantages over the usual avilys connection . This is an important Nepal Phone Number List concept you will need to learn to implement . But before you know it, we should first understand “ log in”. And what’s going on inside when we connect to the beehive . Log is a condition that merges records from two tables (or datasets). Suppose we have two tables a and b. When we perform a joint operation, it will return records that are a combination of all the columns of a and b. Now let’s take a look at Nepal Phone Number List the functionality of a regular login with an example. When we apply the login operation. The task will be assigned to the map reduce task, which consists of two stages: a 'map scene' and ' reduce stage '. "Read" the data from the merge tables and pair the " login key" and "Login value" into an intermediate file. In the shuffle step, this intermediate file is Nepal Phone Number List sorted and merged. The task of the reducer in the reduction phase is to take this sorted result into account and perform the joining task. Joining the map side is similar to joining, but all the tasks will be done by the map performer alone. Map-side join is best suited for small tables to optimize a task. How to optimize the task will connect to the map side? Suppose we have two tables, one of which is a small table. When we submit a map minimization task, a map reduce on-premises task will be created before the initial map Nepal Phone Number List reduce login task, which will retrieve the small table data from the hdfs and save it to the hash table. It is paired into a hash table file. In the next step, when the initial map reduce login task is run, it transfers the data in the hash table file to hadoop's distributed cache, which populates each map creator's local disk. So all cartographers can load this permanent hash Nepal Phone Number List table file back into memory and perform the merge work as before. The progress of the optimized map merge is shown in the figure below. After optimization, the small table only needs to be read once. Also, if multiple repeaters are running on the same computer, the Nepal Phone Number List distributed cache only needs to transfer one copy of the hash table file to the computer.
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