"David G. Johnston" <david.g.johnston@xxxxxxxxx> writes: > On Thursday, April 23, 2020, Thomas Kellerer <shammat@xxxxxxx> wrote: >> Plus: scanning idx_tabla_entidad is more efficient because that index is >> smaller. > Really? The absence of 33 million rows in the partial index seems like it > would compensate fully and then some for the extra included columns. On the other hand, an indexscan is likely to end up being effectively random-access rather than the purely sequential access involved in a seqscan. (If the index was built recently, then it might not be so bad --- but the planner doesn't know that, so it assumes that the index leaf pages are laid out pretty randomly.) Moreover, unless the table is mostly marked all-visible, there will be another pile of randomized accesses into the heap to validate visibility of the index entries. Bottom line is that this choice is not nearly as open-and-shut as the OP seems to think. In fact, it's fairly likely that this is a badly designed index, not a well-designed one that the planner is unaccountably failing to use. Both covering indexes and partial indexes are easily-misused features that can make performance worse not better. regards, tom lane
