Version and Platform Compatibility / Other Platforms and Clients

allow_alter_system

• What it does: Controls whether users can execute the ALTER SYSTEM command to modify configuration parameters without editing postgresql.conf directly.
• Why it matters: This parameter is crucial for database security and configuration management. When enabled, ALTER SYSTEM allows runtime configuration changes that persist across restarts by updating postgresql.auto.conf. Disabling this feature ensures that all configuration changes must go through traditional configuration file management, which can be important for compliance, audit trails, and change control processes in strictly managed environments.
• Ideal value & Best Practice: Default on is appropriate for most environments. Set to off in high-security environments or where strict change control procedures require all configuration modifications to go through configuration management tools or direct file edits. When disabled, ensure you have proper processes for configuration management.

transform_null_equals

• What it does: Controls whether expressions of the form expr = NULL are automatically transformed to expr IS NULL.
• Why it matters: This parameter addresses a common SQL compatibility issue. According to SQL standard, expr = NULL should always return NULL (unknown) because NULL represents an unknown value. However, many developers mistakenly expect expr = NULL to behave like expr IS NULL. Enabling this parameter can improve compatibility with applications written with this misunderstanding, but it violates SQL standards.
• Ideal value & Best Practice: Default off (SQL standard compliant). Set to on only for legacy application compatibility where changing application code is not feasible. For new development, keep disabled and educate developers to use proper NULL handling (IS NULL, IS NOT NULL) as this follows SQL standards and avoids confusion.

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