Logical Replication and Logical Decoding
Instead of copying raw disk changes, logical replication sends the meaning of each change: insert this row, update that one.
Because it speaks in rows rather than disk blocks, the two sides can run different PostgreSQL versions, different hardware, even different schemas, and you can copy just the tables you choose.
Pro members see the rest of this lesson
- A 4-step state diagram: Decode → Filter → Identify → Apply
- The full mechanism: what PostgreSQL does internally, in source terms
- 2 SQL queries you can run, each labelled by how it was verified
- The closing insight, the mistake it prevents, and what it changes in your work
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Check it against the source2 citations in postgres/postgres · file, symbol and line verified on REL_17_STABLE
Primary symbol: CreateInitDecodingContext · line 399
Primary symbol: LogicalDecodingProcessRecord · line 88
Anchored to postgres/postgres on REL_17_STABLE and cross-checked against the manual for PostgreSQL 15–18. Every query here was run and its output captured on a throwaway PostgreSQL 17.10 lab; corrections are noted inline. Ch. 49 Logical Decoding in the official docs →
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What comes before, after, and alongside it.
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