PostgreSQL Compatibility Settings Query: Complete Guide to pg_settings Analysis

calendar Sep 3, 2025 / · 3 min read · postgresql database-administration system-catalog compatibility configuration sql-queries database-management pg-settings  ·
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PostgreSQL Compatibility Settings Query: Complete Guide to pg_settings Analysis

This PostgreSQL query extracts compatibility-related configuration parameters from the pg_settings system catalog, providing essential insights into version and platform compatibility settings for database administrators.

Purpose and Overview

The query targets PostgreSQL's pg_settings system view to identify all configuration parameters related to compatibility settings. This is particularly valuable for database administrators managing PostgreSQL installations across different versions, platforms, or when migrating from other database systems.

What This Query Accomplishes

  • Retrieves compatibility-related configuration parameters
  • Displays parameter values, types, and constraints
  • Shows boot values versus current reset values
  • Identifies parameters requiring restart for changes
  • Filters specifically for compatibility categories

Code Breakdown

 1SELECT
 2    name,
 3    setting,
 4    -- category,
 5    vartype,
 6    short_desc,
 7    -- enumvals,
 8    source,
 9    min_val,
10    max_val,
11    boot_val,
12    reset_val,
13    -- not available on PostgreSQL < 9.5
14    pending_restart
15FROM
16    pg_settings
17WHERE
18    -- Version and Platform Compatibility / Previous PostgreSQL Versions
19    -- Version and Platform Compatibility / Other Platforms and Clients
20    category ILIKE '%Compatibility%';

Key Column Explanations

name: The configuration parameter name (e.g., standard_conforming_strings, transform_null_equals)

setting: Current value of the parameter as it appears in the configuration

vartype: Data type of the parameter (bool, integer, string, enum, real)

short_desc: Brief description explaining the parameter's purpose

source: Origin of the current setting (default, configuration file, command line, etc.)

min_val/max_val: Minimum and maximum allowed values for numeric parameters

boot_val: Default value established at server startup

reset_val: Value the parameter will have after a configuration reload

pending_restart: Indicates if the parameter change requires a server restart

Key Insights and Use Cases

Database Migration Support

This query helps identify compatibility settings when migrating from other database systems or upgrading PostgreSQL versions. Parameters like standard_conforming_strings and escape_string_warning are crucial for application compatibility.

Version Compatibility Analysis

Understanding which compatibility settings are active helps maintain consistent behavior across different PostgreSQL versions, especially important in environments with multiple database instances.

Performance and Behavior Tuning

Compatibility settings can impact both performance and application behavior. This query provides visibility into current configurations affecting legacy application support.

Common Compatibility Parameters

Standard Conformance Settings

  • standard_conforming_strings: Controls interpretation of backslash escapes in string literals
  • transform_null_equals: Treats expr = NULL as expr IS NULL

Legacy Support Parameters

  • array_nulls: Controls recognition of NULL elements in arrays
  • backslash_quote: Controls use of backslashes in quoted strings

Platform-Specific Settings

Parameters that ensure consistent behavior across different operating systems and client platforms.

Best Practices

Regular Monitoring

Execute this query regularly to ensure compatibility settings remain appropriate for your environment and applications.

Documentation

Maintain documentation of why specific compatibility settings are configured, especially when deviating from defaults.

Testing

Always test compatibility setting changes in development environments before applying to production systems.

Version Planning

Review compatibility settings when planning PostgreSQL version upgrades to identify potential application impacts.

Advanced Usage

Filtering by Source

Add AND source != 'default' to see only explicitly configured parameters.

Restart Requirements

Filter by pending_restart = true to identify settings requiring restart.

Specific Categories

Modify the WHERE clause to target specific compatibility subcategories or combine with other parameter categories.

Troubleshooting

Parameter Not Found

If expected compatibility parameters don't appear, verify your PostgreSQL version supports them and check the exact category names.

Access Permissions

Ensure your database user has sufficient privileges to query system catalogs.

Version Differences

Some columns like pending_restart are only available in PostgreSQL 9.5 and later versions.

References

PostgreSQL Documentation - Server Configuration - Official documentation covering all PostgreSQL configuration parameters and their usage

PostgreSQL System Catalogs Documentation - Comprehensive guide to PostgreSQL system catalogs including pg_settings

PostgreSQL Compatibility Settings Guide - Detailed explanation of compatibility and version-specific configuration options

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