Avoid full page images in streaming replication?

ISTM it should be possible to avoid sending full page writes to a
streaming replica once the replica has reached a consistent state. I
assume that the replica would still need to write full pages to it's
disk in case of a crash, but the sender could insert special WAL records
to tell it when to do so, instead of sending the full page image.
Presumably this would be a big win for replication over a WAN.

Am I missing something? I see that pglesslog is no longer supported but
couldn't find any particular reason for that...
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Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com