On Thu, May 2, 2024 at 9:38 AM Peter Eisentraut <pe...@eisentraut.org> wrote: > On 30.04.24 14:39, Daniel Verite wrote: > > postgres=# SELECT '.foo.' like '_oo' COLLATE ign_punct; > > ?column? > > ---------- > > f > > (1 row) > > > > The first two results look fine, but the next one is inconsistent. > > This is correct, because '_' means "any single character". This is > independent of the collation.
Seems really counterintuitive. I had to think for a long time to be able to guess what was happening here. Finally I came up with this guess: If the collation-aware matching tries to match up f with the initial period, the period is skipped and the f matches f. But when the wildcard is matched to the initial period, that uses up the wildcard and then we're left trying to match o with f, which doesn't work. Is that right? It'd probably be good to use something like this as an example in the documentation. My intuition is that if foo matches a string, then _oo f_o and fo_ should also match that string. Apparently that's not the case, but I doubt I'll be the last one who thinks it should be. -- Robert Haas EDB: http://www.enterprisedb.com
