> I've already used an 'EXPLAIN ANALYZE' to post the message. So I don't > clearly understand what you are expecting for, when you tell me to provide > 'EXPLAIN ANALYZE' (please excuse me for the misunderstood)
No, you haven't. You've provided 'EXPLAIN' output, but that just prepares an execution plan and displays it. So it shows just estimates of row counts etc. and not actual values.
Do the same thing but use 'EXPLAIN ANALYZE' instead of 'EXPLAIN' - it will run the query and provide more details about it (run time for each node, actual number of rows etc.).
Anyway the sudden changes of estimated costs are suspicious ...