MongoDB vs PostgreSQL 15 Key Differences

Jun 15, 2022
MongoDB vs PostgreSQL

Since databases are a basic base for software development and they serve various purposes for building projects of all kinds and size, it's important to understand the importance of databases in order to select an appropriate database structure to your stack.


What exactly is MongoDB?

The MongoDB logo, showing the text beside an upright, green leaf.
MongoDB logo. (Image Source: Mecdata)

Main Descriptions

There are some key characteristics of MongoDB that have earned it a spot among the best non-relational databases in the markettoday:

  • Tips for performance: As your applications change, MongoDB assists you with the best available schema design techniques to achieve peak effectiveness.
  • Multiple cloud clusters Utilizing MongoDB allows you to build resilient and powerful applications which leverage two or more cloud clusters at the same time.
  • Load-balancing: MongoDB facilitates control concurrently to handle multiple client requests in parallel with other servers. This will help reduce the burden on servers while ensuring data consistency and availability and allows for scaling applications.

Use Cases

MongoDB is wielded by thousands of organizations worldwide for data storage needs or as their applications' database services.

MongoDB plays a pivotal role in:

  • Content management Content management with HTML0: With MongoDB it is possible to serve and store any type of content, construct any feature, and incorporate any type of information within one database. MongoDB sets the stage for success by providing standard hardware and more efficient teams that can make your projects costs 10% less than they should while offering all the tools needed for creating apps that are rich in content.
  • Personalization: MongoDB allows you to personalize the experiences for millions of clients at any time, by implementing specific features like targeted advertisements, customized home pages, and sign-on to social media networks. There is also the option of running complex queries directly on your database without having to worry about transformation the data, extracting it, or loading.
  • Offloading of the mainframe It's easy to move workloads off the mainframe with MongoDB. Offloading of the mainframe is the process of replicating commonly accessed mainframe data to the operating data layer (ODL) built upon MongoDB, against which operations can be transferred from other applications.

What exactly is PostgreSQL?

The PostgreSQL logo, showing the text below a stylized blue elephant head outlined in black and white.
PostgreSQL Logo. (Image Source: Uberconf)

Despite the increasing use of NoSQL databases, traditional databases are still useful for a variety of applications due to of their strength and robust capabilities for querying.

The relational database is great for processing complex queries and data-driven reporting in cases where the structure of data doesn't change frequently. Open-source databases like PostgreSQL are a great option for a reliable production-quality database compared to its counterparts that are licensed, such as SQL Server and Oracle.

PostgreSQL also carries no fees for licensing, which eliminates the possibility of over-deploying. Its committed group of fans and contributors regularly find bugs and solutions, chipping in for the overall security of the database system.

The Main Features

Below are some of the most notable aspects of PostgreSQL which make it one of the most frequently used databases in the world today:

  • Columns that are not atomic one of the primary constraints of an underlying relational model is that columns have to be atomic. PostgreSQL, however, doesn't have this constraint and allows columns to contain sub-values which queries easily gain access to.
  • The support of HTML0 of JSON data The capability to store and query JSON permits PostgreSQL to run NoSQL tasks as well- say, if you're creating a database that stores information from multiple sensors but aren't sure of which columns are required to be supported by different types of sensors. In this case you could create tables where one of the columns is JSON for storing the continuously evolving or non-structured data.
  • Window Functions: PostgreSQL window functions are a key element in making them a popular choice for analytics applications. Windows functions perform functions over multiple rows and return the identical number of rows. Window functions are different from aggregate functions due to the fact that aggregate functions can only provide a single row upon aggregation.

Use Cases

Below are a few scenarios that illustrate how PostgreSQL is useful:

  • Database that is a federated hub: PostgreSQL's JSON support as well as foreign data wrappers allow it to interface with different data stores -- including NoSQL kinds -- as well as serve as a federated hub for polyglot database systems.
  • Science data Research and scientific projects could generate huge amounts of datathat need to be managed most effectively and efficiently. PostgreSQL offers a wonderful SQL engine, with strong analytics capabilities, making the processing of large quantities of data just a piece cake.
  • LAPP open-source stack: PostgreSQL can run dynamic applications and websites as part of a robust alternative to the LAMP stack. LAPP stands for Linux, Apache, PostgreSQL, Python, PHP, and Perl.

MongoDB vs PostgreSQL: Head-to-Head Comparison

The main issue isn't MongoDB against PostgreSQL however, it's the top document database vs the most reliable relational database.

Most of the time, at the beginning of a developing project, the leaders are aware of the usage case, however they don't have clarity regarding what features specific to the application clients and customers will require. The end result is that they have to make a decision and trust that it's the best fit.

In the next section in the next section, we'll explain the distinctions in MongoDB and PostgreSQL in order to assist you in making the right choice easily. This information is based upon important factors such as architecture, ACID compliance, extensibility as well as security, replication and support, just to name a few.

Let's get started!

ACID Compliance

One of the most pivotal attributes of relational databases which help write applications is ACID transactions. When it comes to level of isolation within transactions in databases are related, PostgreSQL uses the read committed isolation level as default. Additionally, users can adjust the isolation level of read committed level to the serializable isolation level.

Important to remember the importance of transactions is that they allow various changes to a database that can be implemented or rolled back in the context of a group. So, for an a relational database, information would be modelled over separate parent and child tables within a tabular schema.

In contrast, document databases can are more efficient in executing transactions due to the fact that they combine the information contained in documents. Also, because writing and reading is an atomic operation, it doesn't need a multi-document transaction.

MongoDB supports complete isolation while a document is being updated. In the event of an error, the update procedure to roll back, reversing the change as well as ensuring that clients receive a similar image of the document.

MongoDB also supports database transactions across multiple documents. This allows pieces of changes related to them to be rolled back or committed as a group. Owing to its multi-document transactions ability, MongoDB is one of the few databases to coalesce the speed, flexibility, and power that the model of documents offers along with the ACID guarantees of traditional databases.

Architecture/Document Model

In the case of storing data within fields such as subdocuments and arrays that are nested similar information within JSON documents can be stored in a logical way for easy query access through mongodb. mongoDB query languages.

With MongoDB it is possible to store data as documents in a binary format known as binaries JSON (BSON). Fields can differ based upon the documents they're catering to, therefore, you don't need to disclose the structure of documents for the database Documents are self-decribing.

If you want to add the new field in any document, then it is possible to create the field with no impact on other documents in the collection. You can also update the ORM or central system catalog.

MongoDB gives you the possibility of schema validation in order to establish data governance controls over every collection. This feature is useful when combining data from diverse sources and accommodating changes to documents as they evolve, especially as the new application functionality is consistently deployed.

PostgreSQL has a client-server type of architecture. It consists of the following two steps:

  • Client-side processes This is the applications leveraged by users to connect to the database. Most often, they have an interface for users that is simple and is used to communicate between users and databases by means of APIs.
  •    Server-side processes    The application is called "Postgres" application that tackles connections, operations static, dynamic and assets. The running PostgreSQL site is managed by a Postmaster daemon, an centralized coordinating system. The postmaster daemon is responsible for:
  • Recovering from an accident
  • Initiating the server
  • The server must be shut down
  • Background running processes
  • Handling connection requests from brand new clients

.

Extensibility

The term "expansibility" refers to the fact of being designed to facilitate the expansion of functions or capabilities.

PostgreSQL supports extensibility in several ways, like stored functions and processes. What is what makes PostgreSQL expansive is its operation driven by catalogs.

The databases of relational types typically contain information about databases, tables and columns. within catalogs of system information. These "data dictionary" appear to the user as tables, but they contain information that is stored internal within the database system.

PostgreSQL stores the information regarding the columns and tables, as well as details about the types of data, functions, and access techniques available.

More: PostgreSQL can also incorporate user-written code into itself via dynamic loading. In most cases, users require certain functionality that can be implemented via shared libraries. It is easy for users to provide the code and PostgreSQL will download it whenever necessary, which makes it uniquely suited for rapid prototypes of brand new apps.

On the other hand, MongoDB has eventually become adaptable, which allows users to develop their functions and use these functions within the framework. It's equivalent to user-defined functions (UDF) which allow users of relational databases (like PostgreSQL) to extend SQL statements.

Collaboration and Agility

MongoDB uses a document model that makes development and collaboration quicker and easier to use. MongoDB is primarily using JSON or BSON to save its information as documents.

BSON comprises a range of different data types not present in JSON information, including DateTime, long, int, and byte array that help handle information more effectively since it can be customized depending on the data type instead of treating all data as a universal "number" type. The BSON format makes queries run more quickly since it's an encapsulation format that archives JSON-like documents.

BSON skips the keys that aren't useful for the query, making it easier to find the data. A user could further establish the document's structure, and make some changes by introducing new fields, changing data, or developing it whenever they see fit.

This flexibility is a huge advantage for MongoDB since it can help avoid delays caused by asking the administrator to restructure the data definition language statements and then starting from scratch by recreating or reloading the database.

MongoDB also makes it easy for developers to collaborate with teams. This means there's no need for intermediation or complex communication between teams.

In terms of collaboration, PostgreSQL offers user-level permissions, role inheritance, and table-level privileges. It is possible to manage users and grant them read and write rights.

Additionally, you are able to review various groups or users' access to data activities using the option to audit which gives an extra layer of security. However, PostgreSQL isn't as speedy as MongoDB since it's a relational database that stores data in rows and columns.

Foreign Key Support

A key feature that sets MongoDB apart from PostgreSQL is the way it goes about storage of its data.

Because it's not a relational database, MongoDB employs collections in place of tables. Foreign keys are an array of attributes within the table which refer to the key in another table. The foreign key ties these two tables to each another.

Since there are no tables in MongoDB, there are no foreign keys within MongoDB as well, which is why there aren't any restrictions on foreign keys. But, MongoDB does have a DBRef standard that helps to standardize the creation of the references.

Partitioning and Sharding

Partitioning and sharding is essentially the process of breaking large data sets into subsets of smaller. Sharding means that data is stored across multiple computers while partitioning groups this data within a single database.

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MongoDB is scalable because of the partitioning of data among instances in the cluster. The database doesn't break the data in pieces since they're distinct units which makes it much easier to share them among multiple servers. Data is stored locally.

Data is distributed over different regions with ease via MongoDB Atlas' cloud services. It is also possible to store your data within specific regions or globally regions to ensure reduced latency.

From the version 5.0, MongoDB has included an "live" Resharding feature which is a significant time saver because you just need to set a policy. The database can automatically redistribute the data when the time arrives.

In the past, it was possible to do so without taking the system down, but the process was complicated and extremely risky. While MongoDB was able to provide global geo-partitioning for some time the data was expanding across different countries at various rate. Live resharding can be useful for data that must stay local within a country.

In contrast, PostgreSQL supports declarative partitioning that is basically the method of specifying how to divide a table into partitions. The table that is divided is called the partitioned table The specification is comprised of the partitioning method, and the list of columns or the expressions that are used is called"the key to partition.

It is possible to implement partitioning using a range, where tables can be divided by ranges defined through a key column or collection of columns. This ensures none of the different ranges of values assigned to different partitions.

You can also use list partitioning in which the table is split in accordance with the key value defined.

Replication

Replication involves making copies of the same dataset on more than one server. This allows database administrators to ensure high redundancy of data and high reliability of data.

For MongoDB the way to achieve this is with the help of a "replica set" that is which is a cluster that's synchronized, consisting of 3 or more servers that continue to replicate data among them. It provides redundant protection against any downtime that might be experienced in the case of an scheduled maintenance break or a system failure, thus increasing the fault tolerance that the database has.

Replica sets are able to be deployed across various data centers too since they could be useful in the event there are regional downtimes. This can be done by MongoDB Atlas, which makes designing and configuring the clusters simpler and quicker.

PostgreSQL provides primary and secondary replication. Write-ahead logs enable sharing the changes that are made to the replica nodes, thus making asynchronous replication feasible. The other types of replications comprise logical replication, streaming replication and physical.

Indexes

Indexes are structures or objects that allow us to retrieve certain rows of information or rows faster.

PostgreSQL offers a variety of different types of indexes to match any query workload efficiently. The techniques used to index comprise B-tree, multicolumn and expressions. Additionally, advanced and partial indexing techniques including GiST, KNN Gist, SP-Gist GIN, BRIN, covering indexes and bloom filters are also possible within PostgreSQL.

On the other hand, MongoDB allows you to store data in any structure that can be quickly accessed through indexing, regardless of how deeply nested in documents or arrays.

Language & Syntax

Both MongoDB and PostgreSQL provide support for a wide range of languages.

Normalization

Normalization is the procedure of organizing a relational database in order to minimize redundancy in data as well as minimizing anomalies that occur during modifications to data, and enhance accuracy of the data.

MongoDB is able to handle both normalized and denormalized models of data (also known as embedded models).

Embedded models let applications save related data in the same database record that will provide greater efficiency for reading operations as well as the ability to retrieve relevant data within a single database transaction.

Furthermore, you can also change related data using one atomic write as applications use fewer queries to complete common operations. Documents in MongoDB that use the embedded data model must be smaller than the maximum BSON document size (16 MB).

Normalized data models describe relationships using references between documents. This would be beneficial to embedding, especially when it results in data duplication but insufficient benefits to read speed outweigh the effects of duplicates.

But, denormalization generally results in high memory usage the previously normalized data within databases is combined to increase performance.

PostgreSQL schemas are identified by relationship. It is possible to identify the structure with a 1:1, 1:many or many:1 relationship. Data normalization can prove beneficial since it eliminates duplicate copies of data, thus assuring security.

Performance

MongoDB was built to expand horizontally because it typically combines its power with additional machines and doesn't rely on the processing power. MongoDB is capable of supporting massive applications, regardless of being defined by data size or users.

MongoDB can be used in situations that demand the speedy processing of queries. It can also manage a huge amount of data. The database could include several hundred machines.

Since MongoDB 4.4, queries implemented against replica sets deliver better and more predictable results through "hedged" reads. These reads are directed to multiple nodes within the replica set until the most efficient node is able to respond.

PostgreSQL, while it isn't as efficient as MongoDB in terms of its pure insertion speed, is a step ahead when it comes to ACID compatibility. Transactions are handled securely and efficiently, which allows the entire process to fail instead of executing a write that partially succeeded.

MongoDB has only recently (with version 4) started to support ACID transactions, which is similar as SQL databases.

Unlike MongoDB, PostgreSQL depends on the strategy of scaling up (vertical scaling) for data volumes and the ability to write in a larger scale. It's performed by adding more hardware resources like disks, CPUsand memory an existing database server.

Price

PostgreSQL is totally free and is open source. This means that anyone can utilize the features available and add modifications to the code with ease whenever needed.

MongoDB is also an open-source tool. But, MongoDB does have other choices, including the enterprise version or Atlas (for Cloud), which have varying prices. A pricing model on premises is available with the MongoDB enterprise edition.

Mongo RealmDB is available for free for every Atlas users for testing and light usage, enabling developers to create and publish mobile apps.

MongoDB Realm pricing options compute, sync, request, and transfer listed in a tabular format.
Pricing options available for Mongo RealmDB. (Image source: MongoDB Pricing)

Data migration may also generate overhead; however, it is a standard procedure regardless of the database you have implemented within your system.

Processing of Query

PostgreSQL uses the model of a relational database which relies on the storage of data in tables, and using the structure query language (SQL) for database access. SQL commands can be performed using the PostgreSQL console psql. It has a large object feature, that provides stream-like access to the user's data which is kept in a specific large-object structure.

Prior to adding data, the database schema must be constructed to provide an understanding of data relationships to process the query. The related information is stored separately in tables of the database. This can be accessed via foreign keys and joins.

It's not easy to alter the layout of the database once it's loaded. It needs several teams in development, ops, and the database administrator to manage the changes that are implemented to the structure in a controlled manner.

On the other hand, the data structure of MongoDB doesn't need to be designed beforehand since it is dealing with data that's not structured. Additionally, the data structure is much easier to modify.

Developers are able to select what's important for the application, and implement the changes required. MongoDB uses MQL, which allows you to interact with documents in MongoDB and take out information while offering the versatility and performance that SQL does.

MongoDB processes data as JSON documents. The user can search for fields in the JSON document as well. So, MongoDB is quite useful in cases where you want to save documents in a flexible data field.

In contrast, PostgreSQL utilizes the GROUP_BY function to run and process aggregate queries MongoDB typically uses aggregation pipelines for processing the queries.

One major drawback of MongoDB However, the main drawback is that you can't easily join tables. In PostgreSQL this is made easy through the use of JOIN statements.

MongoDB has tried to solve the problem by offering multi-dimensional data types that can embed one document store within another. But, the system isn't well-organized and not as elegant as the straightforward join function which PostgreSQL incorporates.

Security

PostgreSQL offers tons of authentication methods including a modular pluggable authentication system (PAM) as well as a lightweight directory access protocol (LDAP), both of which can reduce the attack surface of servers. The system also provides protection for servers with host-based authentication, as well as certificate authentication.

The level of security could differ from one cloud system to one, even though it's the identical database.

Additionally, MongoDB has client-side and field-level encryption. This allows users to protect their data before transmitting it to the database through the network. However, as the data is stored as key-value pairs in one record It is not protected by the same level of security provided by PostgreSQL; MongoDB's main focus remains on speed.

Community & Support

PostgreSQL is open-source and has been embraced by the community, which strengthens it as a whole ecosystem. PostgreSQL often releases updates regularly, and users, developers, or third-party companies help and develop the system through fixing issues or minor changes to the database platform.

As with PostgreSQL, MongoDB also has an online community that allows users to communicate with others and have answers to their questions. MongoDB's enterprise support is similar to PostgreSQL. MongoDB support for enterprise customers can provide a comprehensive database of knowledge, including use-cases extensive tutorials, in-depth tutorials, tips on optimizing, as well as the best practices.

There are also online classes that offer the training and certifications offered by MongoDB at no cost.

Challenges

While we've discussed the features in both MongoDB and PostgreSQL which make these databases popular with developers, they do come with their number of flaws too.

MongoDB tends to focus on speedy data operations, but isn't as secure in data protection that PostgreSQL seems to possess. It's quite tasking on the memory as denormalization typically causes a high consumption of memory.

In addition, since there is no support for joins, MongoDB databases are oversupplied with data -- often in duplicate data, thereby burdening the memory. MongoDB is also trying to integrate interpretation into other query languages to increase the extensibility of its database, but it could slow down performance as the database wasn't originally built to support relationships in data models.

The conversion of SQL to MongoDB queries may take additional time for the engine to be used, and could slow down the implementation and development.

On the other hand however, even though PostgreSQL is simple to set up and adapts to nearly every platform, its performance can differ depending on the platform. Furthermore, it lacks any tools for revising or reporting that could show the current status of your database. There is a possibility of having to examine your database regularly if something doesn't go exactly as you planned, to prevent noticing a failure when it's too to late.

PostgreSQL is also slower as it focuses on compatibility. While efforts have been made to improve PostgreSQL's speed, the modifications still need a little more development.

MongoDB and PostgreSQL: Which Should You Pick?

MongoDB is a non-relational data source with respect to PostgreSQL is an open-source relational database. While NoSQL databases work on storing the data as key-value pair as one record and relational databases save data on different tables.

If you prioritize faster data integration, and the ability to scale across multiple servers, MongoDB might be a ideal choice for your company.

Summary

In summary to summarize we've discussed the essential details about PostgreSQL and MongoDB similar to each other. We've covered their background, key features, and how they differ.

Although both PostgreSQL and MongoDB are fantastic databases, it ultimately boils down to deciding which one is best for your company.

In between PostgreSQL and MongoDB, which database do you prefer? Please let us know your preference in the comment section!

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