Pushed. I added one comment to explain xmin_frozen also, which
otherwise seemed a bit mysterious. I did not backpatch, though, so
9.6-11 are a bit different, but I'm not sure it's a good idea at this
point, though it should be pretty innocuous.
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Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services