On 12.10.24 00:53, Paul A Jungwirth wrote:
Our docs seem to contrast "streaming replication" to logical, but these are not really opposites. Sometimes when they say "streaming" they mean "physical". Probably this is historical: at first physical replication was the only kind of streaming we had. Personally this has caused me a lot of confusion. For example, recently when I read "Synchronous replication (see Section 26.2.8) is only supported on replication slots used over the streaming replication interface," I took it to mean synchronous replication only worked for physical replication, not logical. But actually here the contrast is between the streaming protocol and SQL commands. I think it would help if the docs elsewhere took more care to say "physical" not "streaming" when that is the meaning. This patch fixes a callout note in the Logical Decoding section. It was sort of vague before. It dates back to the original commit documenting logical decoding, so I'm not sure of the original motive. I think the new text is more precise and about the other use for replication slots, and also clearly separates streaming replication from physical-vs-logical replication. (I used the word "typically" because you *can* have a standby with logical replication, although elsewhere we warn it may not be as robust.) I also tried to fix the first three paragraphs of https://www.postgresql.org/docs/current/runtime-config-replication.html which seem to be setting up a distinction between streaming replication and logical. This is tricky, because (1) we are trying to introduce how we've organized different config parameters, and some affect both physical and logical replication (e.g. max_replication_slots and wal_retrieve_retry_interval) (2) you can use logical replication without streaming (e.g. pg_logical_slot_get_changes). While I was making edits there, I took out some language about "built-in" and "feature", which seem like unnecessary wordiness. I also added "physical" to a couple places in https://www.postgresql.org/docs/current/warm-standby.html as well as a Note callout to clarify that the whole page is really about using physical replication. Technically you could use logical replication to run a standby, but that seems like a separate discussion. Yours,
Adding clear definitions to the glossary would help users and authors alike. J. Purtz
