Allow precision option for postgresql datetimes

This patch addresses the difficulty of retrieving datetime fields. By default, the database holds a higher precision than the time as a String.

This issue is discussed at length at the following links:
- [#3519](https://github.com/rails/rails/issues/3519)
- [#3520](https://github.com/rails/rails/issues/3520)

Also, kudos to @mattscilipoti

1 files changed, 10 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 43e243581c..a9940209fa 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -187,6 +187,7 @@ module ActiveRecord
         case sql_type
         when /^bigint/i;    8
         when /^smallint/i;  2
+        when /^timestamp/i; nil
         else super
         end
       end
@@ -201,6 +202,8 @@ module ActiveRecord
       def extract_precision(sql_type)
         if sql_type == 'money'
           self.class.money_precision
+        elsif sql_type =~ /timestamp/i
+          $1.to_i if sql_type =~ /\((\d+)\)/
         else
           super
         end
@@ -1285,6 +1288,13 @@ module ActiveRecord
             when 5..8; 'bigint'
             else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
           end
+        when 'datetime'
+          return super unless precision
+
+          case precision
+            when 0..6; "timestamp(#{precision})"
+            else raise(ActiveRecordError, "No timestamp type has precision of #{precision}. The allowed range of precision is from 0 to 6")
+          end
         else
           super
         end