Hi, There seems to be a weird bug in Postgres (last tested 11.12) where it allows an INSERT into a table with a UNIQUE / UNIQUE CONSTRAINT index on a TEXT/VARCHAR when there's already a value present in that index, but only for UTF-8 input.
I just had this happen on our user table and it somehow made it so that Postgres returned no results for *any* SELECT ... FROM x WHERE unique_col = 'x', which unfortunately meant no one could login to our service. I had to: SET enable_indexscan = off; SET enable_bitmapscan = off; And then the data was returned properly. I thought maybe the index was corrupt somehow, so I tried to reindex the unique index, which failed because "nur" was present twice. I modified the value in that column by the primary key (which is an integer), and that allowed me to reindex, after which queries against the column started working properly again. My collation settings: postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | I've had this happen before on a different table with cyerrlic UTF-8 input, but didn't really have much to go on debugging wise. What I sort of don't get is... before we insert anything into these tables, we always check to see if a value already exists. And Postgres must be returning no results for some reason. So it goes to insert a duplicate value which somehow succeeds despite the unique index, but then a reindex says it's a duplicate. Pretty weird. Regards, Omar
