Another amusing conversation and somewhat shocking “discovery”.
More poor performing SQL – obviously missing any sort of suitable index (on Oracle).
Me (to developer): Could you add a suitable composite (multi-column) index to table PS_xxxx please for columns C,B and A – there seems to be frequent access using these three columns that would be vastly improved by adding an index.
After a few days I notice new “alternate search key” indexes in the DEV environment. One for each of the columns A, B and C.
Me: Did you add that index?
Developer: Yes, but in the testing I did it wasn’t very much faster.