[davidrowley]

> The one I'd love to tell the planner is that a table holds transactions in time, and that it should not expect that today's data is empty because it was empty 10 hours ago. It's an extremely common pattern, it makes any statistics gathering based on percentage of data changed dubious pretty quickly, and harms a whole lot of real queries, because in data like this, people care the most about the recent data.

It's not a hint, but PostgreSQL does have something that can help with cases like that.

In some cases, to obtain selectivity estimates, the planner will probe a btree index to find the actual lower and/or upper bound. For this to apply, a btree index must exist and you have to be using indexes >, >=, < or <= operator. The planner will probe the index if the query is comparing the indexed column to a value that's known the planner if that value falls on the first or last histogram bucket. This can help when your statistics are slightly out of date and you're querying for some column which stores a monotonically increasing or decreasing value.