Thread by @richardfoote

Fun Poll: At what estimated % of rows does the Oracle CBO automatically decide it too expensive to use an index and not consider associated index based access paths? (use comments if you think it another value). #Oracle #Indexing

Thank you to everyone that voted and/or commented. Interesting results indeed and an indication perhaps some Oracle myths simply refuse to go away. The correct answer is there is NO such % of rows in which the CBO will "automatically" abandon costing possible index related paths.

I first blogged about how the CBO could quite happily select an index that accessed and returned 100% of all rows in a table because it's the cheapest path, way way back in 2008... richardfoote.wordpress.com/2008/05/20/rea…