Ernest E Vogelsinger <ernest@vogelsinger.at> writes:
> (a) creating an index on all three columns, or
> (b) create a single varchar column combining all three components into a
> single string, like "ident1:ident2:nodeid" and indexing this column only.
I can't imagine that (b) is a good idea ... it's dubious that you are
saving anything on the indexing, and you're sure adding a lot of space
to the table, not to mention maintenance effort, potential for bugs,
etc.
It might be worth creating the index so that the "least non-unique"
column is mentioned first, if there's a clear winner in those terms.
That would minimize the number of times that comparisons have to look at
the additional columns.
regards, tom lane
