HBase Interview Questions

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HBase Interview Questions

 

What is the history of HBase?
2006: BigTable paper published by Google.
2006 (end of year): HBase development starts.
2008: HBase becomes Hadoop sub-project.
2010: HBase becomes Apache top-level project.

What is Apache HBase?
Apache Hbase is one the sub-project of  Apache Hadoop,which was designed for NoSql database(Hadoop Database),bigdata store and a distributed, scalable.Use Apache HBase when you need random, realtime read/write access to your Big Data.A table which contain billions of rows X millions of columns -atop clusters of commodity hardware. Apache HBase is an open-source, distributed, versioned, non-relational database modeled after Google’s Bigtable. Apache HBase provides Bigtable-like capabilities  run on top of Hadoop and HDFS.

what is NoSql?
Apache HBase is a type of “NoSQL” database. “NoSQL” is a general term meaning that the database isn’t an RDBMS which supports SQL as its primary access language, but there are many types of NoSQL databases: BerkeleyDB is an example of a local NoSQL database, whereas HBase is very much a distributed database. Technically speaking, HBase is really more a “Data Store” than “Data Base” because it lacks many of the features you find in an RDBMS, such as typed columns, secondary indexes, triggers, and advanced query languages, etc.

What are the main features of Apache HBase?
Apache HBase has many features which supports both linear and modular scaling,HBase tables are distributed on the cluster via regions, and regions are automatically split and re-distributed as your data grows(Automatic sharding).HBase supports a Block Cache and Bloom Filters for high volume query optimization(Block Cache and Bloom Filters).                                                                              hbase interview questions

hbase interview questions

When should we use Hbase?
1)we should have milions or billions of rows and columns in table at that point only we have use Hbase otherwise better to go RDBMS(we have use thousand of rows and columns)
2)In RDBMS should runs on single database server but in hbase is distributed and scalable and also run on commodity hardware.
3) typed columns, secondary indexes, transactions, advanced query languages, etc these features provided by Hbase,not by RDBMS.

What is the difference between HDFS/Hadoop and HBase?
HDFS doesn’t provides fast lookup records in a file,IN Hbase provides fast lookup records for large table.

Is there any difference between HBase datamodel and RDBMS datamodel?
In Hbase,data is stored as a table(have rows and columns) similar to RDBMS but this is not a helpful analogy. Instead, it can be helpful to think of an HBase table as a multi-dimensional map.

What are key terms are used for designing of HBase datamodel?
1)table(Hbase table consists of rows)
2)row(Row in hbase which contains row key and one or more columns with value associated with them)
3)column(A column in HBase consists of a column family and a column qualifier, which are delimited by a : (colon) character)
4)column family(having set of columns and their values,the column families should be considered carefully during schema design)
5)column qualifier(A column qualifier is added to a column family to provide the index for a given piece of data)
6)cell(A cell is a combination of row, column family, and column qualifier, and contains a value and a timestamp, which represents the value’s version)
7)timestamp( represents the time on the RegionServer when the data was written, but you can specify a different timestamp value when you put data into the cell)

What are datamodel operations in HBase?
1)Get(returns attributes for a specified row,Gets are executed via HTable.get)
2)put(Put either adds new rows to a table (if the key is new) or can update existing rows (if the key already exists). Puts are executed via HTable.put (writeBuffer) or HTable.batch (non-writeBuffer))
3)scan(Scan allow iteration over multiple rows for specified attributes)
4)Delete(Delete removes a row from a table. Deletes are executed via HTable.delete)
HBase does not modify data in place, and so deletes are handled by creating new markers called tombstones. These tombstones, along with the dead values, are cleaned up on major compaction.

How should filters are useful in Apache HBase?
Filters In Hbase Shell,Filter Language was introduced in APache HBase 0.92. It allows you to perform server-side filtering when accessing HBase over Thrift or in the HBase shell.

How many filters are available in Apache HBase?
Total we have 18 filters are support to hbase.They are:
ColumnPrefixFilter                                                                                                                            
TimestampsFilter                                                                                                                              
PageFilter                                                                                                                                      
MultipleColumnPrefixFilter                                                                                                                    
FamilyFilter                                                                                                                                    
ColumnPaginationFilter                                                                                                                        
SingleColumnValueFilter                                                                                                                       
RowFilter                                                                                                                                       
QualifierFilter                                                                                                                                 
ColumnRangeFilter                                                                                                                             
ValueFilter                                                                                                                                     
PrefixFilter                                                                                                                                    
SingleColumnValueExcludeFilter                                                                                                                
ColumnCountGetFilter                                                                                                                          
InclusiveStopFilter                                                                                                                           
DependentColumnFilter                                                                                                                         
FirstKeyOnlyFilter                                                                                                                            
KeyOnlyFilter

How can we use MapReduce with HBase?
Apache MapReduce is a software framework used to analyze large amounts of data, and is the framework used most often with Apache Hadoop. HBase can be used as a data source, TableInputFormat, and data sink, TableOutputFormat or MultiTableOutputFormat, for MapReduce jobs. Writing MapReduce jobs that read or write HBase, it is advisable to subclass TableMapper and/or TableReducer.

How do we back up my HBase cluster?
There are two broad strategies for performing HBase backups: backing up with a full cluster shutdown, and backing up on a live cluster. Each approach has pros and cons.
1)Full Shutdown Backup
Some environments can tolerate a periodic full shutdown of their HBase cluster, for example if it is being used a back-end analytic capacity and not serving front-end web-pages. The benefits are that the NameNode/Master are RegionServers are down, so there is no chance of missing any in-flight changes to either StoreFiles or metadata. The obvious con is that the cluster is down.
2)Live Cluster Backup
 live clusterbackup-copytable:copy table utility could either be used to copy data from one table to another on the same cluster, or to copy data to another table on another cluster.
live cluster backup-export:export approach dumps the content of a table to HDFS on the same cluster.

Does HBase support SQL?
Not really. SQL-ish support for HBase via Hive is in development, however Hive is based on MapReduce which is not generally suitable for low-latency requests.By using Apache Phoenix  can retrieve data from hbase by using sql queries.

 

these are the basic hbase interview questions & answers

Comments

  1. Santosh Dandin says:

    HBase isn’t suitable for every problem.

    First, make sure you have enough data. If you have hundreds of millions or billions of rows, then HBase is a good candidate. If you only have a few thousand/million rows, then using a traditional RDBMS might be a better choice due to the fact that all of your data might wind up on a single node (or two) and the rest of the cluster may be sitting idle.

    Second, make sure you can live without all the extra features that an RDBMS provides (e.g., typed columns, secondary indexes, transactions, advanced query languages, etc.) An application built against an RDBMS cannot be “ported” to HBase by simply changing a JDBC driver, for example. Consider moving from an RDBMS to HBase as a complete redesign as opposed to a port.

    Third, make sure you have enough hardware. Even HDFS doesn’t do well with anything less than 5 DataNodes (due to things such as HDFS block replication which has a default of 3), plus a NameNode.

    HBase can run quite well stand-alone on a laptop – but this should be considered a development configuration only.

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