How to Migrate from On-Premise to PostgreSQL

How do I migrate my on-prem database to PostgreSQL?

Move data and schema from an on-premises database into PostgreSQL using pg_dump, pg_restore, and ancillary tools.

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Description

Why migrate an on-prem database to PostgreSQL?

Reduce licensing costs, gain cloud scalability, and use PostgreSQL’s rich extension ecosystem without changing application logic.

Which tools migrate on-premise data to PostgreSQL?

Use pg_dump/pg_restore for logical dumps, pg_upgrade for in-place PostgreSQL upgrades, foreign data wrappers for live replication, and third-party ETL tools when downtime must be near zero.

How do I export my on-premise database?

Using pg_dump for a full logical dump

Run pg_dump on the source host to capture schema and data in one file, keeping referential integrity intact.

Using CSV files and COPY

For massive tables like OrderItems, export to CSV and load with COPY to cut migration time.

How do I create target schemas in PostgreSQL?

Replay the --schema-only dump first so tables such as Customers, Orders, and Products exist before bulk-loading data.

How do I import data into PostgreSQL?

Use pg_restore for custom dumps, or psql -f for plain SQL dumps.For CSVs, issue COPY within a transaction to allow fast rollback on error.

How do I validate the migrated data?

Run row-count comparisons and checksum queries against tables like Customers.Execute end-to-end application tests that read from the new PostgreSQL instance.

What are best practices for zero-downtime cutover?

Enable logical replication from the old system to the new PostgreSQL database, switch application traffic during a short maintenance window, then disable replication.

Can I automate migrations with scripts?

Combine Bash, pg_dump, pg_restore, and psql commands inside CI pipelines so future migrations stay repeatable and auditable.

Why How to Migrate from On-Premise to PostgreSQL is important

How to Migrate from On-Premise to PostgreSQL Example Usage


-- Verify row counts after migration
SELECT
    'Customers'  AS table,
    (SELECT COUNT(*) FROM Customers) AS rows_postgres,
    (SELECT COUNT(*) FROM fdw_source.Customers) AS rows_source;

-- Spot-check five recent Orders
SELECT o.id, c.email, o.total_amount
FROM Orders o
JOIN Customers c ON c.id = o.customer_id
ORDER BY o.order_date DESC
LIMIT 5;

How to Migrate from On-Premise to PostgreSQL Syntax


# Full logical dump
env PGPASSWORD=$SRC_PWD pg_dump \
  --host $SRC_HOST --port 5432 --username $SRC_USER \
  --format=custom --jobs=4 --dbname ecommerce \  # on-prem DB
  --file=ecommerce.dump

# Schema-only preload on target
pg_restore \
  --host $PG_HOST --username $PG_USER --dbname ecommerce \
  --schema-only --jobs=4 ecommerce.dump

# Data load on target
pg_restore \
  --host $PG_HOST --username $PG_USER --dbname ecommerce \
  --data-only --jobs=4 ecommerce.dump

# CSV export for a large table
psql -h $SRC_HOST -U $SRC_USER -d ecommerce \
  -c "COPY OrderItems TO STDOUT WITH CSV" > order_items.csv

# Fast CSV import on PostgreSQL
psql -h $PG_HOST -U $PG_USER -d ecommerce \
  -c "COPY OrderItems FROM STDIN WITH CSV" < order_items.csv

Common Mistakes

Skipping the --schema-only preload causes foreign-key violations during data restore. Always replay schema first, then data.
Running COPY outside a transaction makes rollbacks impossible on error. Wrap large COPY jobs in BEGIN/COMMIT to stay safe.