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HBase Interview Questions

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HBase Interview QuestionsUpdated: March 28, 2018

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Q. What exactly do you know about the Hbase and what exactly do you find different in it as compare to others platforms in its class?
It is one of the best available Database Management systems which are based on Hadoop. As compared to others, it is actually not a relational DBMS and it cannot be considered when it comes to any structured query language. All the clusters are generally managed by a master node in this approach and this is exactly what that makes it simply the best. 

Q. Can you name a few operational commands which are present in Hbase?
These are: Put, Scan, Delete, Get and last is Increment

Q. What would be the best reasons to prefer Hbase as the DBMS according to you?
One of the best things about Hbase is it is scalable in all the aspects and modules. The users can simply make sure of catering a very large number of tables in a short time period. In addition to this, it has a vast support available for all the CRUD operations. It is capable to store more data and can manage the same simply. Also, the stores are column oriented and there are a very large number of rows and column available that enable users to keep the pace up all the time. 

Q. How many tombstone markers are there in the Hbase? Name them
There are total 3 tombstone markers which you can consider anytime. They are Version delete, Family delete and Column Delete. 

Q. Tell a few scenarios when you will consider Hbase?
When there is a need to shift an entire database, this approach is generally opted. In addition to this, during the data operations which are large to handle, Hbase can be consider. Moreover, when there are a lot of features such as inner joins and transactions maintenance need to be used frequently, the Hbase can be considered easily.  

Q. How can you say that the Hbase is capable to offer high availability?
There is a special feature known as region replication. There are several replicas available that define the entire region in a table. It is the load balancer in the Hbase which simply make sure that the replicas are not hosted again and again in the servers with similar regions. This is exactly what that makes sure of the high availability of Hbase all the time. 

Q. What do you mean by WAL?
It stands for Write Ahead Log. It is basically a log which is responsible for recording all the changes in the data irrespective of the mode of their change. Generally, it is considered as the standard sequence file. It is actually very useful to consider after the issues like server crash or failure. The users can still access data through it during such problems. 

Q. Can you tell a few important components of the Hbase that are useful to the data managers?
With Hbase, the users are able to simply handle more amount of data through a special component “Region”. In has another component called as “Zookeeper” which is mainly responsible for the co-ordination of the maser and the client on the other side. There are “Catalog Tables” which consists of Root and Meta Data simply available with them.

Q. Can you directly delete a call from the Hbase?
No, it is not possible in most of the cases. When the users actually do so, the cells get invisible and remain present in the server in the form of a tombstone marker. They are generally removed by the compactions periods. The direct deleting doesn’t work in most of the cases.

Q. What is the significance of Data management according to you?
Generally, organizations have to work with bulk data. When the same is structured or managed, it is easy to utilize or to deploy it for any task. Of course, it cut down the overall time period required to accomplish a task if it is well-managed. The users are always free to keep up the pace simply with the structured or the properly managed data. There are a lot of other reasons too that matters and always let the users assure error-free outcomes. 

Q. What do you know about the set of tables in the Hbase?
They consist of a long series of the rows and columns. It seems quite similar to that of a traditional database.  There is one element in every table and the same is called as the primary key. The columns generally denote an attribute of the concerned objects. 

Q. Can you tell any one basic condition to be fulfilled when it comes to getting the best out from the Hbase?
The users must make sure that there are enough nodes and clusters so that Hbase can perform its task reliably and easily. With more nodes, more efficiency can simply be assured by the users.

Q. Is Hbase an OS independent approach?
Yes, it is totally independent of the operating system and the users are free to consider it on Windows, Linux, Unix etc. the only basic requirement is it should have a Java support installed on it. 

Q. Where the compression feature can be applied in the Hbase?
It is generally done when the users need to use any of the feature related to the physical storage assessment.  There are no complex restrictions that need to be fulfilled for this.

Q. You might have used a relational database, can you tell some of the major differences you noticed in it as compared to Hbase?
Well, the first difference is Hbase is not based on schema whereas relation database is. The automated partitioning can easily be done in Hbase while relational database lack this feature. There are more tables in Hbase than in the relational database. Also, it is a row-oriented data store while Hbase is a column-oriented data store.  

Q. How can you make sure of logical grouping of cells in the Hbase?
This can be assured by paying attention to the Row key. The users are free to make sure that all the cells with similar row key can be located to each other and have the presence on a similar server. If the need of defining is realized, the Row key can be considered. 

Q. Tell something about the procedure of deleting a row in Hbase?
The best part about the Hbase is everything written on the RAM gets stored automatically on the Disk. There are some barring compaction remains present with the same. These compactions can be categorized into two parts and they are major and minor. The major compaction can easily delete the files while there is a restriction on the minor ones for the same. 

Q. What do you know about an Hfile and with whom it is actually related to in an Hbase?
It is basically a defined storage format for the Hbase and generally, it is related to a column family. There is no strict upper limit on them in the column families. The users can easily deploy an Hfile for storing data that belong to different families. 

Q. Is it possible for the users to alter the column family’s block size?
Yes, it is possible. Generally, when this is done by the users, the fresh version of data simply occupies the new block size without affecting the old data. The entire old data consume the new one during the compaction. 

Q. Compare Hbase and Hive and tell the noticeable differences
Both are based on Hadoop but both are different from one another. Hive is generally considered as one of the best available data warehouse infrastructure. The operations of Hbase are limited when compared to the Hive. However, when it comes to handling the real-time operations, the Hbase is good. On the other hand, the Hive is preferred only when the querying of data is the prime need. 

Q. At the record and at the table level, what are the different operational commands you can find?
At table level, the commonly used commands are drop, list, scan and disable whereas on the other side, get, put, scan and increment are the commands related to record level. 

Q. What do you mean by the region server?
Generally, the databases have a huge volume of data to deal with. It is not always possible and necessary that all the data is linked to a single server. There is a central controller and the same should specify the server with which a specific data is concerned with or placed on. The same is known as Region server. It is also considered as a file on the system that let the users display the defined server names which are associated. 

Q. What is standalone mode in the Hbase?
When the users don’t need the Hbase to use the HDFS, this mode can be turned on. It is basically a default mode in the Hbase and the users are generally free to use it anytime they want.  Instead of HDFS, the Hbase make use of a file system when this mode is activated by the user. It is possible to save a lot of time while enabling this mode during the performance of some important tasks. It is also possible to apply or to remove various time restrictions on the data during this mode. 

Q. What is Hbase shell?
It is basically a Java API that is used for establishing a connection with the Hbase. The users need not to worry about anything when it comes to dealing with this problem. Also, the users are free to keep up the pace without worrying about anything about the connectivity when the Hbase shell is deployed.

Q. Tell a few important features of the Apache Hbase?

1. Hbase is capable to be used while performing a lot of tasks which needs modular or linear scaling
2. All the tables are distributed on the cluster through regions. 
3. With respect to the growth in the data, the regions automatically grow and split
4. There are several bloom filters that Hbase support
5. The use of Block Cache in the Hbase is totally allowed
6. Hbase is capable to handle the volume query optimization when the data needs are complex

Q. Name any 5 important filters in Hbase with which you are familiar?
Page Filter, Family Filter, Column Filter, Row Filter and Inclusive Stop Filter 

Q. Is it possible for the users to perform iteration through the rows? Why or why not?
Yes, it is possible. However, when the same task is performed in a reverse order, it is not allowed. This is because the column values are generally stored on a disk and their length should be completely defined. Also, the bytes which are related to the value should be written after it. For performing this task in the reverse order, these values should be stored one more time and this can create compatibility problems and can affect the memory of the Hbase. Thus, it is not allowed. 

Q. Why Hbase is a schema-less database?
This is because the users need not to worry about defining the data prior of the time. You only need to define the column family name and nothing else. This makes the Hbase a schema-less database. 

Q. What is the procedure to write data in the Hbase?
During any modification or change in the data, it is first sent to a commit log which is also known as WAL. It is after this the data is stored in the memory. In case the data exceed beyond the defined limit, the same is transferred to the disk as an Hfile. The users are free to discard the commit logs and can proceed with the stored data. 

Q. Define TTL in Hbase?
It is basically a technique that is useful when it comes to data retention. It is possible for the users to preserve the version of a cell for a defined time period. The same get deleted automatically upon the completion of such a time.

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