Tom Lane wrote:

And you can't just dismiss the issue of wrong cost models and say we can get numbers anyway.

Is there a way to see more details about the cost estimates. EXPLAIN ANALYZE seems to show the total time and rows; but not information like how many disk pages were accessed.

I get the feeling that sometimes the number of rows is estimated
very well, but the amount of disk I/O is way off.

Sometimes the number of pages read/written is grossly
overestimated (if tables lave a lot of locally clustered data)
or underestimated if a sort barely exceeds sort_mem.

Perhaps an EXPLAN ANALYZE VERBOSE that would add info like this:

   Index scan ([...]estimated 1000 pages read)  (actual[...] 10 pages read)

would help track those down?

---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match

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