What Is xmin / xmax?
These are hidden system columns in PostgreSQL used for MVCC tracking. xmin marks the transaction that created a row, while xmax marks the one that deleted it. Useful for conflict detection and auditing.
Why It Matters for PostgreSQL Performance
In PostgreSQL performance work, xmin / xmax affects throughput, latency, or operational reliability depending on workload and configuration.
Practical Benchmarking Context
When benchmarking with pgbench, track how xmin / xmax changes behavior across scale factor, client concurrency, and storage conditions.
Use this term together with workload shape, concurrency level, and scale factor when interpreting pgbench outputs. Isolated values can be misleading without full run context.
Example
Query: SELECT xmin, xmax FROM tablename;