How to Migrate from Oracle Enterprise Edition to PostgreSQL

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How can I migrate from Oracle Enterprise Edition to PostgreSQL?

Move schemas and data from Oracle Enterprise Edition to PostgreSQL with oracle_fdw, native exports, and type mapping.

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Description

Example H2

Example H3

Why migrate from Oracle Enterprise Edition to PostgreSQL?

Cut licensing cost, gain open-source flexibility, and adopt PostgreSQL’s extensibility while keeping relational features your app expects.

Which migration paths work best?

Small databases move fastest with oracle_fdw and COPY. Large or complex setups often combine Oracle Data Pump exports with PostgreSQL import scripts.

How do I install oracle_fdw?

On the PostgreSQL server run apt install postgresql-15-oracle-fdw or build from source against Oracle Instant Client. Restart PostgreSQL to load the shared library.

What connection objects must I create?

Create the extension, server, and user mapping, then import the Oracle schema you need. The next section shows exact syntax.

How do I import e-commerce tables?

Use IMPORT FOREIGN SCHEMA to pull in Customers, Orders, Products, and OrderItems from Oracle into PostgreSQL, preserving column definitions.

How can I convert foreign tables to local tables?

Run CREATE TABLE AS SELECT or COPY (SELECT *) against each foreign table. This copies data into native PostgreSQL storage, removing the Oracle dependency.

What about sequences and triggers?

Re-create Oracle sequences with CREATE SEQUENCE. Translate triggers to PostgreSQL PL/pgSQL or extensions like pg_partman when needed.

How do I validate the migrated data?

Run row-count checks, sample checksums, and business-level queries (e.g., total revenue) on both systems. Differences highlight missing rows or type mismatches.

Best practices for smooth migration

Stage migration in a sandbox, freeze Oracle writes during final cut-over, and update application connection strings atomically to avoid split-brain issues.

Why How to Migrate from Oracle Enterprise Edition to PostgreSQL is important

How to Migrate from Oracle Enterprise Edition to PostgreSQL Example Usage


-- Copy Oracle orders into PostgreSQL and recalculate totals
CREATE TABLE orders AS
SELECT id,
       customer_id,
       order_date,
       total_amount
FROM ORDERS;

-- Confirm migration integrity
SELECT COUNT(*) AS oracle_cnt FROM ORDERS;
SELECT COUNT(*) AS pg_cnt FROM orders;

How to Migrate from Oracle Enterprise Edition to PostgreSQL Syntax


-- 1. Install extension
CREATE EXTENSION oracle_fdw;

-- 2. Create a foreign server pointing to Oracle Enterprise Edition
CREATE SERVER oradb FOREIGN DATA WRAPPER oracle_fdw
OPTIONS (dbserver '//orcl-prod:1521/ORCL');

-- 3. Map a PostgreSQL role to an Oracle user
CREATE USER MAPPING FOR postgres SERVER oradb
OPTIONS (user 'ora_user', password 'secret');

-- 4. Import only e-commerce tables
IMPORT FOREIGN SCHEMA "ECOMMERCE"
    LIMIT TO (CUSTOMERS, ORDERS, PRODUCTS, ORDERITEMS)
    FROM SERVER oradb INTO public;

-- 5. Materialize Customers into PostgreSQL
CREATE TABLE customers AS
SELECT id, name, email, created_at FROM CUSTOMERS;

-- 6. Re-create primary key and sequence
ALTER TABLE customers ADD PRIMARY KEY (id);
CREATE SEQUENCE customers_id_seq OWNED BY customers.id;

Common Mistakes

Migrating without mapping Oracle NUMBER(1) to BOOLEAN. Fix by casting NUMBER(1) columns with <code>::boolean</code> or altering the target column type.
Forgetting to recreate sequences, leading to ID collisions. Always generate PostgreSQL sequences and set <code>DEFAULT nextval()</code> on identity columns.