Support PostgreSQL 10

changelogs/unreleased/42047-pg-10-support.yml

+---
+title: Support PostgreSQL 10
+merge_request: 16471
+author:
+type: added

config/initializers/ar5_pg_10_support.rb

+raise "Vendored ActiveRecord 5 code! Delete #{__FILE__}!" if ActiveRecord::VERSION::MAJOR >= 5
+
+require 'active_record/connection_adapters/postgresql/schema_statements'
+
+#
+# Monkey-patch the refused Rails 4.2 patch at https://github.com/rails/rails/pull/31330
+#
+# Updates sequence logic to support PostgreSQL 10.
+#
+# rubocop:disable all
+module ActiveRecord
+  module ConnectionAdapters
+    module PostgreSQL
+      module SchemaStatements
+        # Resets the sequence of a table's primary key to the maximum value.
+        def reset_pk_sequence!(table, pk = nil, sequence = nil) #:nodoc:
+          unless pk and sequence
+            default_pk, default_sequence = pk_and_sequence_for(table)
+
+            pk ||= default_pk
+            sequence ||= default_sequence
+          end
+
+          if @logger && pk && !sequence
+            @logger.warn "#{table} has primary key #{pk} with no default sequence"
+          end
+
+          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 = #{quote(quoted_sequence)}::regclass")
+              else
+                minvalue = select_value("SELECT min_value FROM #{quoted_sequence}")
+              end
+            end
+
+            select_value <<-end_sql, 'SCHEMA'
+              SELECT setval(#{quote(quoted_sequence)}, #{max_pk ? max_pk : minvalue}, #{max_pk ? true : false})
+            end_sql
+          end
+        end
+      end
+    end
+  end
+end
+# rubocop:enable all

doc/install/requirements.md

@@ -121,7 +121,7 @@ Existing users using GitLab with MySQL/MariaDB are advised to
 
 ### PostgreSQL Requirements
 
-As of GitLab 10.0, PostgreSQL 9.6 or newer (but less than 10) is required, and earlier versions are
+As of GitLab 10.0, PostgreSQL 9.6 or newer is required, and earlier versions are
 not supported. We highly recommend users to use PostgreSQL 9.6 as this
 is the PostgreSQL version used for development and testing.