>On the other hand maximum string size has an effect on Postgres indexes: b-tree (the default) will blow up on strings beyond 4k chars, and this is not statically checked by postgres, it will blow up while trying to insert a string of more than 4k chars.
What do you mean by "blow up" here?
create table foos (col varchar(100000));
create index on foos(col);
insert into foos values (repeat('s', 100000));
What do you mean by "blow up" here?
That works fine.