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0 pointsdijit4y ago0 comments

> PostgreSQL has gotten built-in logical replication only recently, and it's still very annoying. It doesn't replicate schema change statements, so those have to be applied independently by some external system

I’ve been using PostgreSQL built-in replication since 9.1 (when it was introduced) and this is definitely not my experience....

In fact it wouldn’t be possible to apply out of replication changes because (unlike MySQL) Postgres replication forces immutability (the replica nodes cannot become r/w).

The "issue" could potentially be that it's async? But I use postgresql a _lot_ and I've never experienced this.

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atombender4y ago

They're referring to logical replication, which is a relatively new feature.

The original mode of replication merely ships the WAL, which describes binary changes to data files. Every change comes in the form "set page 32435 in <file> to <bytes>", with no distinction between the operations that the changes represent.

Logical replication describes the changes logically. A change may be "insert <column values> into <table>" or "add <column name> of <type> to <table>". Since this format isn't tied to the underlying database file format, it offers greater compatibility between PostgreSQL versions. It also allows other applications to process the log and do things like listen for data changes and ingest them into other databases, queues, etc.

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