Oracle-style analytics, functions, and data can be reproduced in PostgreSQL by using built-in equivalents, extensions, and the oracle_fdw foreign data wrapper.
Most migrations require hierarchical queries (CONNECT BY), analytic functions, DECODE/NVL style expressions, and querying live Oracle data without moving it.
Use the ANSI-standard WITH RECURSIVE
clause. It delivers the same parent-child traversal without proprietary syntax.
WITH RECURSIVE product_tree AS ( SELECT id, name, price, 1 AS level FROM products WHERE id = 1 UNION ALL SELECT p.id, p.name, p.price, pt.level + 1 FROM products p JOIN product_tree pt ON p.parent_id = pt.id) SELECT * FROM product_tree;
Use CASE
, COALESCE
, or NULLIF
. They are ANSI compliant and index-friendly.
SELECT id, COALESCE(email,'no-email@example.com') AS email_fallback FROM customers;
Install oracle_fdw
, create a foreign server, and import the desired schemas. This avoids a bulk migration when you only need read-through access.
1. Install Oracle client libs
2. CREATE EXTENSION oracle_fdw;
3. Define server, user mapping, and foreign tables.
PostgreSQL supports the full SQL:2003 window specification, matching functions like SUM() OVER()
, LAG()
, and RANK()
without extra extensions.
SELECT id, total_amount, RANK() OVER(ORDER BY total_amount DESC) AS sales_rank FROM orders;
Translate proprietary syntax early, freeze DDL on both systems, write exhaustive tests, and use CI pipelines to validate rewritten SQL.
Use ora2pg
for schema/data migration and oracle_fdw
for coexistence. Combine with Galaxy’s AI copilot to speed up query rewrites.
Avoid relying on implicit data type casts and unbounded sequences. Explicitly cast and reset sequence values to align with Oracle’s NUMBER defaults.
Yes. oracle_fdw supports INSERT, UPDATE, and DELETE if your Oracle user has the rights.
No, but it accelerates schema conversion and data export, saving weeks of manual work.
ora2pg can map sequences to PostgreSQL SERIAL
or GENERATED AS IDENTITY
, but verify max values to avoid collisions.