The standard names for indexes in PostgreSQL are:
{tablename}_{columnname(s)}_{suffix}
where the suffix is one of the following:
pkey
for a Primary Key constraint;key
for a Unique constraint;excl
for an Exclusion constraint;idx
for any other kind of index;fkey
for a Foreign key;check
for a Check constraint;
Standard suffix for sequences is
seq
for all sequences
Found here
It was found here:
https://stackoverflow.com/questions/4107915/postgresql-default-constraint-names/4108266#4108266
Copied it to gist just in case (if I forget where to look for it)