PostgreSQL vs Oracle — In-Depth Comparison for DBAs

Overview Comparison Table

Aspect	PostgreSQL	Oracle Database
License	Open Source (PostgreSQL License) — Free forever, no per-core fees	Commercial — Named User Plus or Processor License (starts at millions of baht)
Architecture	Process-per-Connection (fork model)	Shared Memory + Thread-based (SGA/PGA)
MVCC	Tuple-level versioning + VACUUM	Undo Segment (Rollback Segment)
SQL Standard	Very high SQL:2023 compliance	SQL:2023 + proprietary extensions
Max DB Size	Unlimited (tested at petabyte scale)	Unlimited
Community	Open-source community + supporting companies (EDB, Crunchy Data, etc.)	Oracle Corporation + Partner ecosystem

Performance & Query Optimizer

Both PostgreSQL and Oracle use a Cost-Based Optimizer (CBO) to choose Query Execution Plans, but there are important differences:

PostgreSQL Query Planner

• Uses a Statistics Collector to gather column distribution data via ANALYZE
• Supports Parallel Query since version 9.6 — current versions (18.x) support Parallel Seq Scan, Index Scan, Hash Join, Merge Join, and Aggregation
• JIT Compilation (LLVM) since version 11 — accelerates queries with complex expressions
• Tune the Planner directly via work_mem, effective_cache_size, random_page_cost
• pg_stat_statements makes it easy to identify slow queries

Oracle Query Optimizer

• Uses Adaptive Query Optimization that can change plans during execution
• SQL Plan Management (SPM) prevents plan regression — locks in good plans
• Real Application Testing (RAT) tests real workloads before upgrades
• AWR (Automatic Workload Repository) automatically captures performance baselines
• More granular Parallel Query — set Degree of Parallelism (DOP) at the Table, Index, or Session level

Partitioning

Data partitioning is essential for ERP systems handling tens of millions of records.

Feature	PostgreSQL 18	Oracle 23ai
Range Partition	Supported	Supported
List Partition	Supported	Supported
Hash Partition	Supported	Supported
Composite (Sub-partition)	Supported (multi-level)	Supported (Range-Hash, Range-List, etc.)
Automatic Partition	No built-in — use pg_partman extension	Interval Partition automatically creates new partitions when data exceeds range
Partition Pruning	Supported (since PG 11)	Supported
Online Partition Management	ATTACH/DETACH without full table lock (PG 14+)	Online Move/Split/Merge Partition

Replication & High Availability

For ERP systems requiring Disaster Recovery and zero downtime, the choice of replication method is critical.

PostgreSQL

• Streaming Replication — Physical replication at the WAL (Write-Ahead Log) level, built-in since PG 9.0
• Logical Replication — Selectively replicate specific tables or schemas (PG 10+)
• Synchronous Replication — Guarantees zero data loss
• Patroni / repmgr — Widely-used automatic failover solutions (open source)
• No built-in Active-Active Multi-Master — requires extensions like BDR (Bi-Directional Replication)

Oracle

• Data Guard — Physical/Logical Standby with automatic Switchover/Failover (requires paid option)
• Active Data Guard — Read from standby while replication is active (requires additional paid option)
• GoldenGate — Logical replication across platforms with Change Data Capture (CDC) support
• RAC (Real Application Clusters) — Active-Active clustering where all nodes can read and write simultaneously (requires paid option)

JSON & NoSQL Capabilities

Both systems support JSON but take different approaches:

Feature	PostgreSQL	Oracle
Data Type	jsonb — Binary format, indexable, fast query	JSON type + JSON Duality View (23ai)
Indexing	GIN Index on jsonb — Full-text search within JSON	Function-based Index, JSON Search Index
SQL/JSON Path	SQL/JSON standard support (PG 12+)	SQL/JSON standard support
Unique Feature	jsonb operators (@>, ?, #>) — very easy to use	JSON Duality View — view relational tables as JSON documents

PL/pgSQL vs PL/SQL

For DBAs who need to migrate stored procedures from Oracle to PostgreSQL, these are the key differences to watch for:

Feature	PL/pgSQL	PL/SQL (Oracle)
Syntax	Similar to PL/SQL but not 100% identical	Oracle's standard language
Package	No Package support — use Schema + Extension instead	Full Package support (Header + Body)
Autonomous Transaction	No built-in — use dblink or pg_background instead	PRAGMA AUTONOMOUS_TRANSACTION
Exception Handling	EXCEPTION WHEN — similar to PL/SQL	EXCEPTION WHEN
Cursor	Supported — slightly different syntax	Supported — REF CURSOR, SYS_REFCURSOR
Bulk Operations	No FORALL — use INSERT ... SELECT or COPY instead	FORALL, BULK COLLECT

Security

Data security is critical for ERP systems handling financial data, employee records, and customer information.

Feature	PostgreSQL	Oracle
Row-Level Security (RLS)	Built-in (PG 9.5+) — define policies per table	Virtual Private Database (VPD) — requires paid option
Encryption at Rest (TDE)	No built-in TDE — use pgcrypto or OS-level encryption	Transparent Data Encryption — encrypts at tablespace level (requires Advanced Security Option)
Audit	pgAudit extension — logs all SQL statements	Unified Auditing — more granular, multi-level policy support
SSL/TLS	Supported — can enforce SSL per user/database	Supported — Oracle Net encryption
Data Masking	Achievable via Views + RLS — no built-in masking	Data Redaction — real-time data masking (requires paid option)

Monitoring & Tooling

DBAs need good monitoring tools — this is where Oracle has a clear advantage, but PostgreSQL's ecosystem is growing rapidly.

Aspect	PostgreSQL	Oracle
Performance Stats	pg_stat_statements + pg_stat_activity	AWR + ASH + ADDM (Automatic Database Diagnostic Monitor)
Log Analysis	pgBadger — analyzes logs and generates HTML reports	Oracle Enterprise Manager (OEM)
GUI Management	pgAdmin, DBeaver, DataGrip (free/affordable)	Oracle Enterprise Manager Cloud Control (requires paid pack)
Grafana Integration	Very easy — many ready-made dashboards available	Possible but more complex to set up

Total Cost of Ownership (TCO) — The Real Decision Factor

For executives making decisions, the 5-year Total Cost of Ownership is the most important number:

Item	PostgreSQL	Oracle Enterprise
License (5 years)	$0	$150K–$1.5M+ (depending on core count)
Support/Maintenance	$0 (Community) or $15K–$60K/year (Commercial Support)	22% of license cost per year
DBA Salary	$1,500–$3,500/month (Thai market)	$2,300–$5,700/month (Oracle DBAs are harder to find)
Options/Add-ons	All features free — Partitioning, Replication, RLS require no additional purchase	RAC, Data Guard, Advanced Security, Partitioning all require paid options
Infrastructure	Works on any Linux distro, containers, all cloud providers	Oracle Linux/RHEL recommended — license costs may increase in the cloud

When to Choose PostgreSQL / When You Still Need Oracle

Choose PostgreSQL when:

• You want to significantly reduce license costs
• You want all features at one price — Partitioning, Replication, RLS, JSON are all free
• You need flexibility — works with any cloud, containers, Kubernetes
• Your workload is medium to large OLTP that doesn't require RAC
• Your DBA team has Linux/Open Source skills and is ready to learn
• You want to avoid vendor lock-in

You still need Oracle when:

• You require RAC (Active-Active Clustering) — PostgreSQL has no built-in equivalent
• You have extensive PL/SQL legacy code that is difficult or impractical to migrate
• You need Adaptive Query Optimization + SQL Plan Management for highly complex workloads
• Your organization has an existing long-term support contract with Oracle
• You require TDE (Transparent Data Encryption) at the tablespace level

Global Organizations Using PostgreSQL

PostgreSQL won the DBMS of the Year 2023 award from DB-Engines (score increase of 22.5%) and continues to grow steadily — currently ranked #4 worldwide behind Oracle, MySQL, and MS SQL Server with 16.85% market share. Over 48,000 organizations globally use PostgreSQL in production:

Organization	Use Case
Apple	Replaced MySQL in 2010 — default database on macOS Server
Instagram (Meta)	One of the largest PostgreSQL deployments in the world — serving hundreds of millions of users daily
Spotify	Uses PostgreSQL + Cassandra as the core infrastructure for its music platform
Netflix	PostgreSQL in backend systems supporting global streaming
Uber	Large-scale data management for ride-sharing operations
Reddit	Core database for one of the world's top community platforms
Discord	Chat system supporting millions of concurrent users
NASA	Scientific data storage and analysis systems

Case Study — TGO Has Used PostgreSQL with Saeree ERP for Over 14 Years

Thailand Greenhouse Gas Management Organization (TGO) is one of the government organizations that has used PostgreSQL as the core database for Saeree ERP since 2011 — over 14 years of PostgreSQL proving itself in a real production environment:

• Stability — No downtime from database issues
• Performance — Handles all organizational users without problems
• Continuous upgrades — Upgraded from PostgreSQL 9.x to 12 to 14 to 18 without issues
• License cost = $0 over the entire 14 years

PostgreSQL is not "inferior free software" — it is an enterprise-grade database with no license fees. What differs from Oracle is the cost, not the quality.

- Saeree ERP Team

Conclusion

1. Oracle remains the "gold standard" — for organizations that need RAC, TDE, Adaptive Optimizer, and are willing to pay for licenses
2. PostgreSQL has reached enterprise level — with comprehensive features and comparable performance
3. TCO is the deciding factor — Oracle's 5-year license cost could fund DBA salaries + entirely new hardware for PostgreSQL
4. Migration is feasible — Tools like Ora2Pg significantly reduce migration time
5. Stay up to date — Follow the latest patches to maintain system stability

If your organization is considering migrating from Oracle to PostgreSQL or needs database consulting for ERP systems, you can contact our consulting team for a free consultation at no charge.

References

• PostgreSQL Official Documentation
• Oracle Database Documentation
• Ora2Pg — Oracle to PostgreSQL Migration Tool
• PostgreSQL Feature Matrix