Postgres SQL Interview Questions for Experienced/Postgres Interview Questions and Answers for Freshers & Experienced

What is Full Text Search? Is it is supported by Postgresql?

It is the method or technique for the search of a single or collection of computer-stored documents in a full-text database. It can be easily differentiated from searches based on the metadata or on parts of the original texts represented in databases.

Although PostgreSQL is not as advanced as compared to the Elasticsearch and SOLR, both of these are specific for full-text search tools. Whereas in PostgreSQL, full-text search is only a feature and it is a pretty good one.

Posted Date:- 2021-11-08 02:37:34

What are Connector Libraries?

It is a collection of connectors that can be downloaded and customized within any ProcessMaker instance. The ProcessMaker manage and continuously update the connector public library.

Posted Date:- 2021-11-08 02:36:57

Can we create a shared storage PostgreSQL server cluster?

PostgreSQL will not support clustering by using shared storage on SCSI, SAN, iSCSI volume, or other shared media. Such "RAC-style" clustering is not supported. Only the replicated clustering is supported at present.

Posted Date:- 2021-11-08 02:36:15

How can we perform queries through multiple databases?

There is no better way to query a database other than the present one. As PostgreSQL loads database-specific system catalogs, we don't know how a cross-database query should behave. contrib/dblink enables cross-database queries with function calls. Of course, a customer can also establish concurrent connections to various databases and merge client-side results.

Posted Date:- 2021-11-08 02:34:35

What are BRIN indices?

Once the BRIN index has been installed, PostgreSQL will be able to select the minimum and maximum values by reading the selected column for each 8k page of data saved. After that, PostgreSQL will store the page number, the maximum and minimum values of the selected column in the BRIN indexes.

Posted Date:- 2021-11-08 02:32:48

What do you mean by Full-Text search in PostgreSQL?

This refers to the technique or method of searching for a single or a collection of documents stored on a computer in a full-text database. It may be simply distinguished from searches according to metadata or portions of the original texts depicted in the databases. While PostgreSQL is not as advanced as SOLR and Elasticsearch, these two tools are specific to full-text search. While in PostgreSQL, the full-text search is just a feature, and it's quite good.

Posted Date:- 2021-11-08 02:32:20

When should PostgreSQL be avoided?

At the cost of speed, PostgreSQL was built to be expandable and compatible. PostgreSQL may not suit you if your project needs the fastest read operations possible.

Due to its wide range of features and its high adherence to the SQL standard, Postgres may be excessive for simple database configurations. MySQL is the practical choice for operations like read-heavy where we need speed.

While PostgreSQL provides solid support for replication, it is always a relatively new functionality, and certain configurations like primary architecture are only possible with expansions. Replication is an advanced feature of MySQL. Most users feel that replicating MySQL is easier to implement, especially for those without the required experience in administering databases and systems.

Posted Date:- 2021-11-08 02:31:26

What kind of database administration tools do you use in Postgresql?

We have a variety of data administration tools. They are Pgadmin, Psql, Phppgadmin. Phppgadmin is the most popular among them. Most of these tools are web-based interfaces and front-end administration tools.

Posted Date:- 2021-11-08 02:30:05

What are the different improvements in the relational data model through PostgreSQL?

A number of improvements have been made to the simple relationship data model through PostgreSQL. They support arrays that include various values, functions, inheritance, and extensibility. Jargon is different in its object-oriented nature in which tables are known as classes.

Posted Date:- 2021-11-08 02:29:25

Briefly describe the functions of Postgresql.

Functions are an important part of running the code on the server everywhere. Some languages used for programming functions are PL/pgSQL, a native PostgreSQL language, as well as other scripting languages such as Perl, PHP, Python, etc. A statistical language called PL/R can also be used to make functions more efficient.

Posted Date:- 2021-11-08 02:28:49

What is the enable-debug command in PostgreSQL?

The enable-debug command allows you to compile all apps and libraries. Executing this process usually prevents the system, but it also increases the size of the binary file. The debug symbols that are present usually help developers identify bugs and other issues that may occur related to their script.

Posted Date:- 2021-11-08 02:28:05

How are statistics updated within Postgresql?

In PostgreSQL, To update your statistics, a special function known as an explicit "vacuum" call is done. The way to do this is to create a Vacuum where the Analyze option is used to update the stats in Postgresql as shown:

VACUUM ANALYZE;

Posted Date:- 2021-11-08 02:27:36

How can we change the column data type in PostgreSQL?

Using the ALTER TABLE command, we can change a column type.

For example:

ALTER TABLE name_of_the_table

ALTER COLUMN name_of_the_column [SET DATA] TYPE new_data_type;

Posted Date:- 2021-11-08 02:27:03

Compare PostgreSQL with MySQL.

MySQL is the "user-friendly, web developer" database, while PostgreSQL is the "feature-rich and standards-compliant" database. PostgreSQL is freely licensed and part of its community; MySQL is GPL licensed and belongs to Oracle. Beyond this, every user of the database should make their own assessment; free software facilitates comparisons.

Posted Date:- 2021-11-08 02:26:34

How is pgadmin used in PostgreSQL?

Pgadmin is a well-known feature for forming a front-end graphic administration tool. This functionality is available as free software with an artistic license. The latest database administration tool available with an artistic license is Pgadmin iii. It is used to retrieve information, develop, test and continuous maintenance of databases.

Posted Date:- 2021-11-08 02:26:06

Does PostgreSQL run on the cloud?

Yes. Like other open source databases, PostgreSQL is easy to run in virtual containers and is highly portable. Several companies have support for PostgreSQL in cloud hosting environments, including Heroku, GoGrid and Joyent.

Posted Date:- 2021-11-08 02:25:20

Why do I get the error -error: memory exhausted in allocsetalloc ()?

You probably have run out of virtual memory on your system, or your kernel has a low limit for certain resources. Try this before starting the server:

Ulimit -D 262144 Limit Datasize 256m

Posted Date:- 2021-11-08 01:58:44

What is table partitioning?

In PostgreSQL, table partitioning is a process in which a large table is divided into smaller pieces called partitions. PostgreSQL supports ranges and lists partitioning through table inheritance. Users must create every partition like a child table in the main table.

Posted Date:- 2021-11-08 01:57:51

What is a CTID of PostgreSQL?

In PostgreSQL, the CTID field is one that exists in each and every PostgreSQL table, and it is unique for all records inside a table, which is used to denote the location of the tuples.

Posted Date:- 2021-11-08 01:57:25

What are the ODBC drivers that are available for PostgreSQL?

plsqlODBC is the official PostgreSQL driver. Besides that, there are other third-party ODBC drivers such as Devart, which shall cost you some money.

Posted Date:- 2021-11-08 01:56:34

What is inverted file in PostgreSQL?

In PostgreSQL, an Inverted file is basically an index data structure used for mapping content to its location to a database file, within a document, or in sets of documents.

It is usually composed of all the distinct words found in a text and a list containing the occurrences of a word in the text.

The inverted file is widely used in a data structure for document retrieval systems in supporting a full-text search.

Posted Date:- 2021-11-08 01:55:30

How are stats updated in Postgresql?

PostgreSQL tokens are the building blocks for any source code. They include a lot of special character symbols. A token represents an identifier, a quoted identifier, a keyword, a special character symbol or a literal symbol.

Posted Date:- 2021-11-08 01:54:50

What is Multi Version Concurrency Control in PostgreSQL?

Multi-Version Concurrency Control (MVCC) is an advanced method used in PostgreSQL for improving the performance of a database in a multi-user environment. Unlike lock models in other databases, PostgreSQL uses a multi-version environment in which locks that are acquired for reading data don’t conflict with locks acquired for writing the data. Hence, making the process more compartmentalized and a lot faster.

Posted Date:- 2021-11-08 01:53:24

What is the Maximum size for a database in PostgreSQL?

PostgreSQL has no maximum database size, so users can put unlimited data into it. But, the table, row, and field size are limited. The row and indexes are also universal for its users.

PostgreSQL usually stores its desk facts in chunks of 8KB. The quantity of these blocks is confined to a 32-bit signed integer, giving the most desk dimension of 16TB.

Posted Date:- 2021-11-08 01:52:59

What does GEQO stands for in PostgreSQL?

In PostgreSQL, GEQO stands for Genetic Query Optimization. It allows the PostgreSQL search query optimizer to support large joined queries in an effective manner using a non-exhaustive search technique.

Posted Date:- 2021-11-08 01:52:25

What are the tokens?

Token are the building blocks of any source code. They are known to comprise many of the special character symbols. These can be regarded as constant, quoted identifiers, other identifiers, and keywords. Tokens which are keywords, consist of pre-defined SQL commands and meanings. Identifiers are used to represent variable names like columns, tables etc.

Posted Date:- 2021-11-08 01:51:33

What is A Ctid?

CTIDs is a field, which exists in every PostgreSQL table and is known to identify specific physical rows according to their block and offset positions within a particular table. They are used by index entries to point to physical rows. It is unique for each record in the table and easily denotes the location of a tuple. A logical row’s CTID changes when it is updated, so the CTID cannot be used as a long-term row identifier. However, it is sometimes useful to identify a row within a transaction when no competing update is expected.

Posted Date:- 2021-11-08 01:51:13

What are the indices of PostgreSQL?

These are inbuilt functions or methods like GIST Indices, hash table and B-tree, which the user can use to scan the index in a backward manner. Users can also define their indices of PostgreSQL.

Posted Date:- 2021-11-08 01:50:48

What is command enable-debug?

The command enable-debug is used to enable the compilation of all the applications and libraries. The execution of this procedure usually impedes the system, but it also amplifies the binary file size. Debugging symbols that are present generally assist the developers in spotting the bugs and other problems which may arise associated with their script.

Posted Date:- 2021-11-08 01:50:31

What is DELETE statement in PostgreSQL?

DELETE statement is used to delete rows from the table.

Posted Date:- 2021-11-08 01:50:10

What is TRUNCATE used for?

TRUNCATE TABLE statement is used to remove all data quickly and efficiently from the table.

Posted Date:- 2021-11-08 01:49:41

Name data types which are used in PostgreSQL.

PostgreSQL supports the following data types:

* Booloean
* Character (char, varchar, text)
* Numeric (Integer, Floating-point)
* Temporal (date, time, timestamp, interval)
* Array (array string, number)
* JSON
* hstore (key-value pair)

Posted Date:- 2021-11-08 01:49:26

What are the indices?

PostgreSQL offers a number of index types: Hash, B-tree, GiST, SP-GiST, BRIN and GIN. Each type of index will use a different algorithm which is most suitable for different types of queries. CREATE INDEX will create B-tree indexes by default that match the most popular situations. Users can set their PostgreSQL indexes as well.

Posted Date:- 2021-11-08 01:47:18

Explain about string constants?

String constant contains a sequence of characters bound by single quotes. This feature is used during insertion of a character or passing character to database objects. PostgreSQL allows the usage of single quotes but embedded by a C style backslash. This feature is important in parsing data.

Posted Date:- 2021-11-08 01:46:57

What are the various enhancements to the straight relational data model by PostgreSQL?

There are various enhancements provided to the straight relational data model by postgre SQl they are support for arrays which includes multiple values, inheritance, functions and extensibility. Jargon differs because of its object oriented nature where tables are called as classes.

Posted Date:- 2021-11-08 01:46:42

Does Postgresql have SPs/ Stored Procedures?

PostgreSQL doesn't have Stored Procedures directly.

However, by working with Object Relational Database Management Systems i.e., PostgreSQL have not necessarily the function Stored Procedure (SP) defined, as we can find in most of other types of DBMS.

They are in fact, small sets of code stored at server side of a database.

On the contrary, to what happens in other databases, the Stored Procedures in PostgreSQL are defined as FUNCTIONS, as well as triggers, making this feature a bit more complicated, depending on its return type. These functions are important and variant in features, but created equal. Working with the creation of these small snippets of code is a good practice because it can leave quite complicated code acting on the server-side that can be used by multiple apps, thus avoiding the need to replicate them in each of these apps.

Posted Date:- 2021-11-08 01:46:20

Is it possible to create a shared storage PostgreSQL server cluster?

Since no one type of clustering satisfies all needs, they have several different clustering tools which take various clustering approaches. The open source projects PostgresXC and Postgres-XL are available, as well as open source forks and proprietary tools such as Greenplum Database, Citus Data and several others.

Also, PostgreSQL is supported by filesystem-based clustering systems for failover, including ones from Red Hat, Microsoft, Veritas and Oracle.

Posted Date:- 2021-11-08 01:45:33

How do we perform queries using Multiple Databases?

There is no way to query a db other than the existing database. Because PostgreSQL loads database specific system catalogs, it is uncertain how a cross-database query should even behave for Postgres.

However, contrib or dblink allows cross-database queries using function calls. Nevertheless, a client can also make simultaneous connections to different databases and merge the results on the client side.

Posted Date:- 2021-11-08 01:45:15

What is write ahead logging?

Postgres’ write ahead logging increases the reliability (in a way resiliency) of the db by logging changes before any changes or updates to the database. This provides log of database in case of a db crash and this also helps to start the work from the point it was discontinued. This it is useful for crash recovery.

Posted Date:- 2021-11-08 01:44:57

What is the purpose of table space in PostgreSQL?

It is a location in the disk. In this, PostgreSQL stores the data files, which contain indices and tables, etc.

Posted Date:- 2021-11-08 01:44:33

What is a non-clustered index?

In a non-clustered index, the index rows order doesn’t match the order in actual data.

Posted Date:- 2021-11-08 01:44:19

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