On Thu, Feb 6, 2020 at 11:04 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > So it appears to me that what commit 6bf0bc842 did in this area was > not just wrong, but disastrously so. Before that, we had a macro that > evaluated isinf(val) before it evaluated the inf_is_valid condition. > Now we have check_float[48]_val which do it the other way around. > That would be okay if the inf_is_valid condition were cheap to > evaluate, but in common code paths it's actually twice as expensive > as isinf().
Well, if the previous coding was a deliberate attempt to dodge this performance issue, the evidence seems to be well-concealed. Neither the comments for that macro nor the related commit messages make any mention of it. When subtle things like this are performance-critical, good comments are pretty critical, too. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
