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  • Book Overview & Buying PostgreSQL 10 Administration Cookbook
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PostgreSQL 10 Administration Cookbook

PostgreSQL 10 Administration Cookbook

Buy this Book
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PostgreSQL 10 Administration Cookbook

PostgreSQL 10 Administration Cookbook

Buy this Book

Overview of this book

PostgreSQL is a powerful, open source database management system with an enviable reputation for high performance and stability. With many new features in its arsenal, PostgreSQL 10 allows users to scale up their PostgreSQL infrastructure. This book takes a step-by-step, recipe-based approach to effective PostgreSQL administration. Throughout this book, you will be introduced to these new features such as logical replication, native table partitioning, additional query parallelism, and much more. You will learn how to tackle a variety of problems that are basically the pain points for any database administrator - from creating tables to managing views, from improving performance to securing your database. More importantly, the book pays special attention to topics such as monitoring roles, backup, and recovery of your PostgreSQL 10 database, ensuring high availability, concurrency, and replication. By the end of this book, you will know everything you need to know to be the go-to PostgreSQL expert in your organization.
Table of Contents (19 chapters)
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Title Page
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Title Page
Copyright and Credits
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Copyright and Credits
Packt Upsell
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Packt Upsell
Contributors
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Contributors
Preface
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Preface
Free Chapter
1
First Steps
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First Steps
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Introduction
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Getting PostgreSQL
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Connecting to the PostgreSQL server
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Enabling access for network/remote users
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Using graphical administration tools
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OmniDB
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Using the psql query and scripting tool
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Changing your password securely
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Avoiding hardcoding your password
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Using a connection service file
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Troubleshooting a failed connection
2
Exploring the Database
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Exploring the Database
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Introduction
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What version is the server?
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What is the server uptime?
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Locating the database server files
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Locating the database server's message log
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Locating the database's system identifier
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Listing databases on this database server
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How many tables are there in a database?
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How much disk space does a database use?
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How much disk space does a table use?
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Which are my biggest tables?
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How many rows are there in a table?
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Quickly estimating the number of rows in a table
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Listing extensions in this database
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Understanding object dependencies
3
Configuration
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Configuration
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Introduction
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Reading the fine manual
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Planning a new database
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Changing parameters in your programs
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Finding the current configuration settings
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Which parameters are at non-default settings?
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Updating the parameter file
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Setting parameters for particular groups of users
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The basic server configuration checklist
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Adding an external module to PostgreSQL
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Using an installed module
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Managing installed extensions
4
Server Control
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Server Control
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Introduction
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Starting the database server manually
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Stopping the server safely and quickly
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Stopping the server in an emergency
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Reloading the server configuration files
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Restarting the server quickly
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Preventing new connections
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Restricting users to only one session each
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Pushing users off the system
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Deciding on a design for multitenancy
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Using multiple schemas
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Giving users their own private database
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Running multiple servers on one system
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Setting up a connection pool
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Accessing multiple servers using the same host and port
5
Tables and Data
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Tables and Data
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Choosing good names for database objects
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Handling objects with quoted names
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Enforcing the same name and definition for columns
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Identifying and removing duplicates
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Preventing duplicate rows
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Finding a unique key for a set of data
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Generating test data
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Randomly sampling data
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Loading data from a spreadsheet
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Loading data from flat files
6
Security
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Security
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Introduction
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The PostgreSQL superuser
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Revoking user access to a table
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Granting user access to a table
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Granting user access to specific columns
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Granting user access to specific rows
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Creating a new user
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Temporarily preventing a user from connecting
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Removing a user without dropping their data
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Checking whether all users have a secure password
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Giving limited superuser powers to specific users
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Auditing database access
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Always knowing which user is logged in
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Integrating with LDAP
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Connecting using SSL
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Using SSL certificates to authenticate
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Mapping external usernames to database roles
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Encrypting sensitive data
7
Database Administration
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Database Administration
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Introduction
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Writing a script that either succeeds entirely or fails entirely
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Writing a psql script that exits on the first error
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Using psql variables
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Placing query output into psql variables
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Writing a conditional psql script
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Investigating a psql error
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Performing actions on many tables
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Adding/removing columns on a table
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Changing the data type of a column
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Changing the definition of a data type
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Adding/removing schemas
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Moving objects between schemas
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Adding/removing tablespaces
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Moving objects between tablespaces
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Accessing objects in other PostgreSQL databases
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Accessing objects in other foreign databases
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Updatable views
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Using materialized views
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Monitoring and Diagnosis
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Monitoring and Diagnosis
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Providing PostgreSQL information to monitoring tools
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Real-time viewing using pgAdmin or OmniDB
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Checking whether a user is connected
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Checking whether a computer is connected
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Repeatedly executing a query in psql
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Checking which queries are running
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Checking which queries are active or blocked
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Knowing who is blocking a query
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Killing a specific session
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Detecting an in-doubt prepared transaction
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Knowing whether anybody is using a specific table
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Knowing when a table was last used
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Usage of disk space by temporary data
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Understanding why queries slow down
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Investigating and reporting a bug
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Producing a daily summary of log file errors
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Analyzing the real-time performance of your queries
9
Regular Maintenance
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Regular Maintenance
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Controlling automatic database maintenance
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Avoiding auto-freezing and page corruptions
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Removing issues that cause bloat
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Removing old prepared transactions
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Actions for heavy users of temporary tables
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Identifying and fixing bloated tables and indexes
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Monitoring and tuning vacuum
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Maintaining indexes
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Adding a constraint without checking existing rows
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Finding unused indexes
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Carefully removing unwanted indexes
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Planning maintenance
10
Performance and Concurrency
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Performance and Concurrency
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Introduction
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Finding slow SQL statements
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Collect regular statistics from pg_stat* views
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Finding out what makes SQL slow
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Reducing the number of rows returned
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Simplifying complex SQL queries
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Speeding up queries without rewriting them
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Discovering why a query is not using an index
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Forcing a query to use an index
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Using parallel query
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Using optimistic locking
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Reporting performance problems
11
Backup and Recovery
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Backup and Recovery
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Introduction
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Understanding and controlling crash recovery
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Planning backups
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Hot logical backups of one database
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Hot logical backups of all databases
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Backups of database object definitions
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Standalone hot physical database backup
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Hot physical backup and continuous archiving
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Recovery of all databases
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Recovery to a point in time
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Recovery of a dropped/damaged table
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Recovery of a dropped/damaged database
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Improving performance of backup/recovery
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Incremental/differential backup and restore
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Hot physical backups with Barman
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Recovery with Barman
12
Replication and Upgrades
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Replication and Upgrades
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Replication concepts
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Replication best practices
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Setting up file-based replication – deprecated
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Setting up streaming replication
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Setting up streaming replication security
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Hot Standby and read scalability
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Managing streaming replication
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Using repmgr
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Using replication slots
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Monitoring replication
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Performance and synchronous replication
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Delaying, pausing, and synchronizing replication
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Logical replication
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Bi-directional replication
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Archiving transaction log data
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Upgrading minor releases
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Major upgrades in-place
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Major upgrades online
Other Books You May Enjoy
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Other Books You May Enjoy
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Leave a review - let other readers know what you think
Index
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Index

Checking whether a user is connected

Here, we will show you how to learn whether a certain database user is currently connected to the database.

Getting ready

If you are logged in as a superuser you will have full access to monitoring information.

How to do it…

Issue the following query to see whether the bob user is connected:

SELECT datname FROM pg_stat_activity WHERE usename = 'bob';

If this query returns any rows, then it means bob is connected to the database. The returned value is the name of the database to which the user is connected.

How it works…

PostgreSQL's pg_stat_activity system view keeps track of all running PostgreSQL backends. This includes information such as the query that is being currently executed, or the last query that was executed by each backend; who is connected; when the connection, the transaction, and/or the query were started; and so on.

There's more…

Please spend a few minutes reading the PostgreSQL documentation, which contains more detailed information about pg_stat_activity...

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