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DatabasePostgreSQLMigration

Migrating from Oracle to PostgreSQL: A Practical Guide

Brian Foley

Why PostgreSQL?

PostgreSQL is the world's most advanced open-source relational database. It supports nearly every feature Oracle offers — partitioning, materialized views, full-text search, JSON, and more — without the licensing costs that can run into six or seven figures annually.

The Migration Process

A successful Oracle-to-PostgreSQL migration follows a structured process:

  1. Schema Assessment — Catalog every table, view, index, constraint, and sequence. Identify Oracle-specific data types (NUMBER, VARCHAR2, CLOB) and map them to PostgreSQL equivalents.
  2. Stored Procedure Conversion — PL/SQL to PL/pgSQL is the heaviest lift. While syntactically similar, there are subtle differences in exception handling, cursor behavior, and package structures that require careful refactoring.
  3. Data Migration — Use tools like ora2pg for the initial lift, then validate row counts, checksums, and referential integrity.
  4. Application Layer Updates — Update connection strings, ORM configurations, and any raw SQL queries that use Oracle-specific syntax.

Common Pitfalls

The biggest mistakes we see: underestimating stored procedure complexity, skipping performance testing under realistic load, and trying to do a big-bang migration instead of an incremental approach.