Interview Q&A / PostgreSQL
PostgreSQL interview questions
Indexes, EXPLAIN, transactions and isolation, JSONB and the Postgres specifics backend interviews probe.
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- What are xmin and xmax on a PostgreSQL row?
They are hidden system columns recording the transaction ID that created the row version (xmin) and the one that deleted or replaced it (xmax). MVCC uses them to decide which versions a given snapshot may see.
IntermediateQuick answer1 min read