Support for query splitting to Replica in core

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This is a very important issue, especially for high-traffic websites.

+1

Hi folks,

I've had a look at the patch and it's pretty much the direction I was going in, I'd start work on it locally before checking the issue queue...

Having reached the same point, I started to think about it bit more... regarding SqlContentEntityStorage, I think it could be a good idea to separate out the read operations from the write options.

I'm thinking SqlContentEntityStorage could become a facade with two underlying objects, a reader and a writer. That way, instead of introducing more execution paths to the code in the class "if we're reading, use a replica, if we're writing, use default", we can just pass the database.replica to the reader, safe in the knowledge that it'll get default if no replica's are configured and pass default through to the writer.

Before I go off and attempt to carve this out, I just thought I'd share the idea to see if sounds sensible to anyone else?

We have a few high-traffic sites and could use this functionality.