Interview Questions.

Question 1. What Is Apache Tajo?

Answer :

Apache Tajo is a relational and allotted information processing framework. It is designed for low latency and scalable advert-hoc question evaluation.

Tajo helps general SQL and diverse records codecs. Most of the Tajo queries may be finished with none amendment.
Tajo has fault-tolerance through a restart mechanism for failed duties and extensible question rewrite engine.
Tajo plays the essential ETL (Extract Transform and Load technique) operations to summarize huge datasets saved on HDFS. It is an alternative preference to Hive/Pig.
Question 2. Mention The Salient Features Of Apache Tajo ?

Answer :

Some salient feaures of Tajo are:

Superior scalability and optimized overall performance
Low latency
User-defined features
Row/columnar garage processing framework.
Compatibility with HiveQL and Hive MetaStore
Simple facts glide and smooth preservation.
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Question three. What Are The Benefits Of Apache Tajo?

Answer :

Apache Tajo gives the following advantages:

Easy to use
Simplified architecture
Cost-primarily based query optimization
Vectorized query execution plan
Fast transport
Simple I/O mechanism and helps numerous sort of storage.
Fault tolerance
Question 4. How Can We Launch A Tajo Cluster?

Answer :

To launch the tajo grasp, execute start-tajo.Sh.

$ $TAJO HOME/sbin/start-tajo.Sh

After then, you can use tajo-cli to access the command line interface of Tajo. If you want to a way to use tsql, study Tajo Interactive Shell report.

$ $TAJO HOME/bin/tsql

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Question 5. Explain Tajo Configuration Files?

Answer :

Tajo’s configuration is based totally on Hadoop’s configuration gadget.

Tajo uses two config documents:

catalog-website.Xml- configuration for the catalog server.

Tajo-web page.Xml- configuration for other tajo modules. Tajo has a selection of inner configs. If you don’t set some config explicitly, the default config might be used for for that config. Tajo is designed to use just a few of configs in typical instances. You won't be involved with the configuration.

In default, there is no tajo-website online.Xml in $TAJO/conf directory. If you place a few configs, first replica $TAJO_HOME/conf/tajo-website.Xml.Templete to tajo-web page.Xml. Then, upload the configs on your tajo-website online.

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Question 6. Explain About Tajo Worker Configuration?

Answer :

Worker Heap Memory Size: The environment variable TAJO_WORKER_HEAPSIZE in conf/tajo-env.Sh allow Tajo Worker to apply the required heap memory size. If you want to alter heap memory size, set TAJO_WORKER_HEAPSIZE variable in conf/tajo-env.

Sh with a right size as follows:

TAJO_WORKER_HEAPSIZE=8000

The default length is one thousand (1GB).

Temporary Data Directory: TajoWorker shops temporary information on nearby file device because of out-of-middle algorithms. It is possible to specify one or more transient statistics directories wherein transient information can be stored.

Maximum range of parallel strolling obligations for every worker: Each employee can execute multiple tasks at a time. Tajo permits customers to specify the maximum range of parallel going for walks obligations for each employee.

Question 7. Explain About Catalog Configuration?

Answer :

If you want to personalize the catalog provider, replica $TAJO_HOME/conf/catalog-website online.Xml.Template to catalog-website online.Xml. Then, add the following configs to catalog-site.Xml. Note that the default configs are enough to launch Tajo cluster in most instances.

Tajo.Catalog.Master.Addr - If you want to launch a Tajo cluster in dispensed mode, you need to specify this deal with. For extra element information, see Default Ports.

Tajo.Catalog.Keep.Magnificence - If you need to trade the persistent storage of the catalog server, specify the class call. Its default cost is tajo.Catalog.Save.DerbyStore. In the current model, Tajo provides three persistent garage classes as follows:

tajo.Catalog.Shop.DerbyStore - this garage magnificence makes use of Apache Derby.

Tajo.Catalog.Keep.MySQLStore - this garage class makes use of MySQL.

Tajo.Catalog.Store.MemStore - that is the in-memory garage. It is simplest utilized in unit assessments to shorten the length of unit assessments.

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Question eight. What Are The Data Formats Supported By Apache Tajo?

Answer :

Apache Tajo supports the following statistics codecs:

JSON
Text report(CSV)
Parquet
Sequence File
AVRO
Protocol Buffer
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Question 9. What Are The Storage Supported By Tajo?

Answer :

Tajo supports the following garage formats:

HDFS
JDBC
Amazon S3
Apache HBase
Elasticsearch
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Question 10. Explain The Tajo Architecture?

Answer :

Client: Client submits the SQL statements to the Tajo Master to get the result.

Master: Master is the principle daemon. It is responsible for query planning and is the coordinator for workers.

Catalog server: Maintains the table and index descriptions. It is embedded within the Master daemon. The catalog server makes use of Apache Derby because the storage layer and connects via JDBC purchaser.

Worker: Master node assigns project to employee nodes. TajoWorker strategies data. As the quantity of TajoWorkers increases, the processing potential additionally increases linearly.

Query Master: Tajo master assigns question to the Query Master. The Query Master is chargeable for controlling a dispensed execution plan. It launches the TaskRunner and schedules tasks to TaskRunner. The predominant position of the Query Master is to display the going for walks responsibilities and document them to the Master node.

Node Managers: Manages the resource of the employee node. It comes to a decision on allocating requests to the node.

TaskRunner: Acts as a neighborhood question execution engine. It is used to run and screen query process. The TaskRunner methods one task at a time.

It has the following three fundamental attributes:

Logical plan - An execution block which created the assignment.

A fragment - an input course, an offset range, and schema.

Fetches URIs:

Query Executor: It is used to execute a question.

Storage provider: Connects the underlying records garage to Tajo.

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Question 11. Mention Some Basic Tajo Shell Commands?

Answer :

Start server

$ bin/begin-tajo.Sh

Start Shell

$ bin/tsql

List Database

default> l

List out Built-in Functions

default> df

Describe Function: df characteristic call - This question returns the whole description of the given function.

Default> df sqrt

Quit Terminal

default> q

Cluster Info

default&> admin -cluster

Show grasp

default> admin -showmasters

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Question 12. What Are Apache Tajo Sql Functions?

Answer :

Some of the SQL capabilities supported by means of Apache Tajo are classified into:

Math Functions
String Functions
DateTime Functions
JSON Functions
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Question 13. How To Create Database Statement In Apache Tajo?

Answer :

The announcement used to create a database in Tajo is Create Database and the syntax for the assertion is:

CREATE DATABASE [IF NOT EXISTS]

Ex: default> create database if no longer exists take a look at;

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Question 14. How To Drop Database In Apache Tajo?

Answer :

The syntax used to drop a database is -

DROP DATABASE

Ex: take a look at> c default

Question 15. How Tables Are Managed In Apache Tajo?

Answer :

The logical view of the statistics supply is defined as table. The desk consists of numerous residences like logical schema, partitions, URL and so forth. A Tajo desk can be a directory in HDFS, a single report, one HBase table, or a RDBMS table.

The sorts of tables supported through Apache Tajo are:

External desk: External table desires the region belongings while the table is created. For instance, if the statistics is already there as Text/JSON documents or HBase desk, it may be registered as Tajo outside desk. The following query is an instance of external table creation.

Create external desk pattern(col1 int,col2 textual content,col3 int) 

region ‘hdfs://path/to/table';

Internal desk: A Internal table is also known as an Managed Table. It is created in a pre-defined bodily location referred to as the Tablespace.

Create desk table1(col1 int,col2 text);

By default, Tajo uses “tajo.Warehouse.Listing” positioned in “conf/tajo-site.Xml” . Tablespace configuration is used to assign new vicinity for the table.

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Question sixteen. Explain About Tablespace?

Answer :

The locations in the storage system are defined via Tablespace. It is supported for only internal tables. Tablespaces are accessed via their names. Each tablespace can use a one-of-a-kind storage kind. If the tablespace is not distinct then, Tajo uses the default tablespace inside the root listing. Tajo’s inner table statistics can be accessed from another table only. It may be configured with tablespace.

CREATE TABLE [IF NOT EXISTS] 

   [(column_list)] [TABLESPACE tablespace_name]

   [the usage of [with ( = , ...)]] [AS ]

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Question 17. What Are The Different Data Formats Supported By Apache Tajo?

Answer :

Text
JSON
Parquet
RCFile
SequenceFile
ORC
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Question 18. How To Insert Records In Apache Tajo?

Answer :

To insert statistics in the 'take a look at' table, kind the following question.

Db sample> insert overwrite into test select * from mytable;

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Question 19. How To Add Column In Apache Tajo?

Answer :

To insert new column in the “college students” desk, type the subsequent syntax -

Alter desk ADD COLUMN

 modify table students add column grade textual content;

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Question 20. How To Set Property In Apache Tajo?

Answer :

This assets is used to trade the table’s assets.

ALTER TABLE college students SET PROPERTY 'compression.Type' = 'RECORD',

'compression.Codec' = 'org.Apache.Hadoop.Io.Compress.Snappy Codec' ;

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Question 21. What Is Distinct Clause In Apache Tajo?

Answer :

A desk column might also incorporate reproduction values. The DISTINCT key-word can be used to go back best wonderful (exclusive) values.

SELECT DISTINCT column1,column2 FROM desk name;

 choose awesome age from mytable;

Question 22. What Is Having Clause In Apache Tajo?

Answer :

The HAVING clause permits you to specify conditions that filter out which organization effects appear inside the very last results. The WHERE clause places conditions on the selected columns, while the HAVING clause places conditions at the companies created through the GROUP BY clause.

SELECT column1, column2 FROM table1 

     GROUP BY column HAVING [ conditions ]

 choose age from mytable organization through age having sum(mark) > 2 hundred;

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Question 23. How To Create Index Statement In Apache Tajo?

Answer :

The CREATE INDEX statement is used to create indexes in tables. Index is used for instant retrieval of statistics. Current model supports index for only undeniable TEXT codecs stored on HDFS.

CREATE INDEX [ name ] ON table_name (  column_name 

create index student_index on mytable(identity);

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Question 24. What Are The Window Functions Provided By Apache Tajo?

Answer :

The functions that execute on a set of rows and return a unmarried fee for every row are Window capabilities. The Window characteristic in a query, defines the window the usage of the OVER() clause.

The OVER() clause has the following capabilities:

Defines window walls to form organizations of rows. (PARTITION BY clause)
Orders rows inside a partition. (ORDER BY clause)
Some of the window functions are:

rank()
row_num()
lead(cost[, offset integer[, default any]])
lag(value[, offset integer[, default any]])
first_value(price)
last_value(cost)
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Question 25. Explain Different Queries Performed By Apache Tajo?

Answer :

Predicates: To evaluate the proper/false values of the UNKNOWN, an expression used is referred to as Predication. For the search circumstance of WHERE clause and HAVING clause, and constructs that require a Boolean price, predicate is used.

Explain: To achieve a question execution plan with a logical and global plan execution of a statement, Explain is used.

Join: SQL joins are used to mix rows from  or extra tables.

The following are the exceptional styles of SQL Joins:

Inner be part of
 RIGHT  OUTER JOIN
Cross be part of
Self be part of
Natural be part of
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Question 26. Explain Abount Postgresql Storage Handler?

Answer :

Tajo supports PostgreSQL garage handler. It enables user queries to get admission to database objects in PostgreSQL. It is the default storage handler in Tajo so that you can effortlessly configure it.

"spaces": 

"postgre": 

"uri": "jdbc:postgresql://hostname:port/database1"

"configs": 

"mapped_database": “sampledb”

"connection_properties": 

"person":“tajo", "password": "pwd"

Here, “database1” refers back to the postgreSQL database which is mapped to the database “sampledb” in Tajo.

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