Support PostgreSQL 10 `pg_sequence`

Another fix for #28780 based on discussions at #28789

- In PostgreSQL 10 each sequence does not know its `min_value`.
A new system catalog `pg_sequence` shows it as `seqmin`.
Refer https://github.com/postgres/postgres/commit/1753b1b027035029c2a2a1649065762fafbf63f3

- `setval` 3rd argument needs to set to `false` only when the table has no rows
to avoid `nextval(<sequence_name>)` returns `2` where `1` is expected.

- `min_value` is only necessary when the table has no rows. It used to be necessary
since the 3rd argument of `setval` is always `false`.

1 files changed, 9 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 55566f1e34..cb45d7ba6b 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -290,9 +290,17 @@ module ActiveRecord
 
           if pk && sequence
             quoted_sequence = quote_table_name(sequence)
+            max_pk = select_value("select MAX(#{quote_column_name pk}) from #{quote_table_name(table)}")
+            if max_pk.nil?
+              if postgresql_version >= 100000
+                minvalue = select_value("SELECT seqmin from pg_sequence where seqrelid = '#{quoted_sequence}'::regclass")
+              else
+                minvalue = select_value("SELECT min_value FROM #{quoted_sequence}")
+              end
+            end
 
             select_value(<<-end_sql, "SCHEMA")
-              SELECT setval('#{quoted_sequence}', (SELECT COALESCE(MAX(#{quote_column_name pk})+(SELECT increment_by FROM #{quoted_sequence}), (SELECT min_value FROM #{quoted_sequence})) FROM #{quote_table_name(table)}), false)
+              SELECT setval('#{quoted_sequence}', #{max_pk ? max_pk : minvalue}, #{max_pk ? true : false})
             end_sql
           end
         end