Avoiding Unrecognized Configuration Parameters in PostgreSQL Schema Restoration

Problem Statement

When migrating PostgreSQL schemas between databases, you might encounter errors like ERROR: unrecognized configuration parameter "transaction_timeout" when restoring a schema dump. This typically happens when:

• Using pg_dump (version 17+) to dump an older PostgreSQL database (e.g., version 15.7)
• Attempting to restore the dump to another database server of the same older version
• The generated schema dump includes newer configuration parameters like transaction_timeout that don't exist in older PostgreSQL versions

# Schema dump with pg_dump 17.0
pg_dump --schema-only 'postgresql://.../db1' > schema.sql

# Restoration on PostgreSQL 15.7 fails
psql 'postgresql://.../db2' < schema.sql
# ERROR:  unrecognized configuration parameter "transaction_timeout"

Why This Happens

PostgreSQL pg_dump includes version-specific features in its output by design:

1. pg_dump 17+ includes parameters like transaction_timeout introduced in PostgreSQL 17
2. PostgreSQL 15.x doesn't recognize this parameter
3. As per official documentation:
   "It is not guaranteed that pg_dump's output can be loaded into a server of an older major version—not even if the dump was taken from a server of that version"

Recommended Solutions

Method 1: Version-Matched pg_dump (Best Practice)

Use a pg_dump version matching your PostgreSQL server version. This ensures compatibility without modern parameters.

# Example for PostgreSQL 15.7
/path/to/postgres-15/bin/pg_dump --schema-only postgresql://.../db1 > schema.sql

Method 2: Suppress SET Statements in Dump

Use the --no-set flag to exclude configuration parameters and session settings:

pg_dump --schema-only --no-set 'postgresql://.../db1' > clean_schema.sql

TIP

For Docker installations matching server version:
docker run -it --rm postgres:15.7 pg_dump --schema-only "your-connection" > schema.sql

Method 3: Filter Out Unsupported Parameters

For existing dumps, remove unsupported statements with sed:

# Remove specific parameter
sed -i '/^SET transaction_timeout =/d' schema.sql

# Remove all parameter settings
sed -i '/^SET .* =/d' schema.sql

Expected Results

After applying either solution, your schema should restore cleanly:

# Verify clean restoration
psql 'postgresql://.../db2' < clean_schema.sql
# CREATE TABLE...
# ALTER TABLE...
# ... Schema created successfully

Important Considerations

• Version Matching: Always match pg_dump major version to your PostgreSQL server
  
• Feature Detection: Newer pg_dump versions may include other version-specific commands beyond SET
• Minimal Dumps: When only needing structural elements, combine flags:

  pg_dump --no-set --no-owner --no-acl --schema-only

Compatibility Explanation

PostgreSQL version compatibility operates as follows:

Component	Compatibility Rule
pg_dump → Server	Server must be ≥ pg_dump minor version
Server → Restored Server	Restored server must be ≥ original server version
pg_dump → Restored Server	No guarantee for older server versions

WARNING

Using pg_dump from newer versions for older PostgreSQL servers is officially unsupported and may produce invalid dumps.

Key Takeaways

1. Always use matching major versions of pg_dump and PostgreSQL
2. Include --no-set in pg_dump commands when compatibility with older versions is required
3. For infrastructure automation, explicitly specify PostgreSQL versions in toolchains
4. Test schema migrations in staging environments before production deployment

By maintaining version consistency and using proper flags, you can reliably migrate PostgreSQL schemas without compatibility errors.