Cross-database knowledge answering real developer questions. Daily articles, comparisons, and reproducible demos for PostgreSQL, MySQL, Oracle, SQL Server, MongoDB.

PostgreSQL MySQL Oracle SQL Server MongoDB DynamoDB SQLite Cassandra AverageDB
✅ Website deployed and accessible at persistence.oracleai.dev | 🚀 Daily content generation in progress

What We Do

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Daily Articles

Deep technical explanations comparing database implementations. Not just what, but why and how they differ.

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Database Shorts

Quick tips and gotchas in 60 seconds. Perfect for daily learning. PostgreSQL vs MySQL vs Oracle insights.

View Shorts
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Weekly Comparisons

Side-by-side analysis of database features with reproducible benchmarks and practical advice.

See Comparisons
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Reproducible Demos

Docker-based examples you can run locally. See the differences in action with real code.

Run Demos

🚀 Current Focus: MVCC Across Databases

How Multi-Version Concurrency Control works differently in PostgreSQL, MySQL/InnoDB, Oracle, and SQL Server.

  • PostgreSQL: Heap tuples with xmin/xmax
  • MySQL/InnoDB: Rollback segments in undo tablespace
  • Oracle: System Change Number (SCN) with undo segments
  • SQL Server: Version store in tempdb
Read Article

Try It Yourself

🐳 Docker Demo: MVCC Comparison

Run concurrent transactions in PostgreSQL, MySQL, and Oracle to see MVCC in action.

git clone https://github.com/oracleai/mvcc-demo.git
cd mvcc-demo
docker-compose up -d
./run_mvcc_test.sh

📊 Performance Comparison

Compare MVCC performance under concurrent read/write workloads across databases.

# PostgreSQL
pgbench -c 50 -T 300 testdb

# MySQL
sysbench oltp_read_write --threads=50 --time=300 run

Upcoming Content

Topic #2: Foreign Keys

When to use them, performance implications, and implementation differences across databases.

Coming Soon

Topic #3: Primary Keys

Surrogate vs natural keys. UUID, auto-increment, sequence, identity column comparisons.

Coming Soon

Topic #4: Indexing Strategies

B-tree vs Hash vs GIN vs BRIN vs LSM. When each works best across different databases.

Coming Soon