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Big Data Engineering

AWS Data Catalog - Changing the Future of Data Analysis

Chandan Gaur | 28 October 2022

What is AWS Data Catalog?

AWS Data Catalog is a prospering metadata management service nowadays. It offers two forms:

  • Comprehensive 
  • Hive Metastore 

The two may exist parallelly. We can search for all our assets in the lake using a comprehensive data catalog. 

There has always been a no-man land between IT and business. It knows how to work with inputs, but the business knows what it represents. This creates a conflict as neither knows enough about it to use it strategically, and hence emerges a tribal behavior where each guard their pockets of expertise. At a certain point, every company has suffered from this condition over the years. 

An organized record of  assets that uses metadata to help organizations manage their assests. Click to explore about, Data Catalog for Snowflake Benefits and Its Functions

What is a Data Catalog?

Data Catalog can be referred to as a retailer's catalog, but instead of giving information about the product, it gives information about the organization's elements. The consumer of this is present all over the hierarchy. They want to use its full potential of it. Hence, it gives a heavy dose of automation to the data catalog to collect meaningful information about the element imported into the solution. This acts as a bridge between the consumer; hence, emitting the tribal behavior is essential to understand that it does not conform. Still, instead, it plays to identify its uses. The application of conformity is what lives inside the warehouse

Comprehensive AWS Data Catalog

Standard AWS services like AWS Lambda, Amazon ES, and Amazon DynamoDB can create a comprehensive catalog. At a glance, triggered Lambda functions populate the DynamoDB table with metadata and object names. When saving it and the object name into Amazon S3, the Amazon ES may search for desired assets. It contains all information about the assets ingested into the S3 lake.

HCatalog with AWS Data Catalog

Hive-compatible Metastore can be created using AWS Amazon Glue for the asset stored in an Amazon S3-based lake. Building your data catalog is a piece of cake with the help of AWS glue. To begin with, go to the AWS management console and register your asset source with AWS glue. The Crawler crawls over the S3 bucket, searches your input sources, and devises a catalog using classifiers. You can choose from many classifiers, such as CSV, JSON, and Parquet, or add your classifiers or choose classifiers from the AWS glue community to add them to the Crawler to recognize different types. AWS glue then spawns a data catalog that can be used by various AWS services such as Amazon Athena, Amazon EMR, Amazon Redshift Spectrum, and Amazon Redshift, and the third-party analytics tools that use a standard Hive Metastore.

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Connections in AWS Glue Data Catalog

It stores connection information for a particular data store. Creating a connection takes the burden off the shoulder to specify connection details every time you create a crawler or job. Different types of connections are available with it, such as JDBC, Amazon RDS, Amazon Redshift, MongoDB, and Amazon DocumentDB. While creating a crawler or ETL job for any source, specify the connection to use.

Populating the AWS Glue Data Catalog

It references data used as a source and target for your ETL (extract, transform, and load) jobs. It must be cataloged to create your warehouse. The information is used to monitor ETL jobs. Each metadata table specifies a single where we store our information.


A table in AWS Data Catalog is a definition representing a store that may hold the object of Amazon S3 service and relational tables in Amazon RDS (Relational Database Service). We can create Tables manually or by using the AWS Data Catalog Crawlers. While defining a table in AWS glue, it provides you with the option of a partitioning key that allows you to partition the table to improve query performance. While partitioning the table, these conditions must be proper. The schemas of the files must be similar. As determined by AWS Glue, the data and the file compression format are the same.


After adding a table in AWS glue, we add it to a database. In AWS Data Catalog organizes, tables into different categories. To do so, we can use a crawler or login to the AWS glue console. Database in AWS glue acts as a container for the defined table created when you manually run a column or add a table. You can visualize the whole thing as an interlinked chain. It may hold the object of Amazon S3 service, and relational tables in Amazon RDS are present in the table contained in the data catalog.

Steps to Work with Database

Various functions can be performed from the database tab in the AWS glue console:

  1. To create a new database, select Add, and provide the description.
  2. To edit action allows you to edit the database.
  3. To delete action allows you to delete it.
  4. View tables action allows you to view the list of tables.

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What is AWS Data Catalog Crawler?

A crawler is the most basic method used by most AWS Glue users to populate the data catalog. The Crawler crawls multiple datastore. On completion, it creates and updates the table that is further used by ETL jobs. The following workflow depicts how a crawler populates the management.

  1. A crawler runs all custom classifiers that you decide to infer the format and blueprint of your information. You give the code to custom classifiers, which run in the request you specify.
  2. The primary custom classifier to effectively perceive the structure of your data is utilized to make a schema. Custom classifiers ranking lower in the list are skipped. If no custom classifier matches your schema, built-in classifiers attempt to perceive your data's schema. An illustration of a built-in classifier perceives JSON.
  3. The crawler interfaces with the store. It may require connection properties for crawler access.
  4. Your assets create the inferred schema.
  5. The Crawler composes metadata for management. The table contains it. The table is written in a database, a compartment of tables in the Catalog. Properties of a table incorporate classification, which might be a label made by the classifier that derived the table schema.

AWS Cloudformation: A Way to Populate AWS Data Catalog

AWS cloud formation service can create many AWS resources. Cloudformation can automate creating an object, making it convenient to define and create AWS Glue objects and other related AWS resources.AWS CloudFormation provides a simplified syntax in JSON/YAML to create AWS resources. CloudFormation can provide templates that may be used to define Data Catalog objects, databases, tables, partitions, crawlers, classifiers, and connections. AWS CloudFormation provides a simplified syntax in JSON/YAML to create AWS resources. It provides templates that may be used to define Data Catalog objects, tables, partitions, crawlers, classifiers, and connections. AWS CloudFormation helps in provisioning and configuring resources described by the template.

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One should now be clear how AWS Data Catalog has helped in strategically using assets by both business and IT, using the serverless environment that makes it easier for one to populate the data catalog. One now knows different types of AWS Data Catalog services (Comprehensive and HCatalog) and how we can populate them. Future Workspace for a reason, right?