Logical replication theory and concepts
summary
Explains how PostgreSQL converts WAL bytes into row-level operations using a reorder buffer and logical decoder, sends only committed transactions, and applies changes on an active target via a WAL receiver that produces new WAL there. Shows initial sync using a replication slot + COPY snapshot, details how the slot holds LSNs and catalog tuples, and demonstrates error loops (receiver quits on missing table, busy replication slot when slots collide). Warns that retained WAL and xmin pressure can cause disk bloat or txid wraparound; no built-in DDL or bidirectional replication yet.
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chapters (8)
- 0:00Introduction - Logical Replication
- 1:18Physical/Streaming Replication
- 4:34Logical Replication
- 7:25WAL Sender (Logical Change Sender)
- 10:00Logical Receiver
- 11:03Replication Slot
- 21:10When things Go Wrong (Error Loops)
- 25:50Conclusion - Use Cases, Limitations & Things to Watch for
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