After importing data in PostgreSQL, duplicate key value violates unique constraint

Question

I recently migrated my rails app to PostgreSQL in order to take advantage of fulltext search.

Since the migration coincided with moving to a new webhost, the steps for m

Answer 1

You can automate wildplasser's solution so that all sequences are synchronized with the current maximum value of their associated column:

do
$block$
declare 
  r        record;
  stmt     text;
  max_id   integer;
begin
  for r in (
              select *
              from (
                select table_schema, 
                       table_name, 
                       column_name, 
                       pg_get_serial_sequence(table_schema||'.'||table_name, column_name) as col_sequence
                from information_schema.columns
                where table_schema not in ('pg_catalog', 'information_schema')
              ) t
              where col_sequence is not null
        ) 
  loop
    stmt := 'select coalesce(max('||r.column_name||'), 0) + 1 from '||r.table_schema||'.'||r.table_name;
    execute stmt into max_id;
    raise notice 'Next ID for %.%.% is %', r.table_schema, r.table_name, r.column_name, max_id;
    perform setval(r.col_sequence, max_id); 
  end loop;
end;
$block$

Note that this will only work if the columns have been defined as serial, bigserial or have been made the "owner" of a sequence.