Agree that propagating the data-type directly from the database is ideal. That's what's being done in the 2 places I found where type-casting was being performed:
- For attributes drawn from schema columns (see #read_attribute @columns_hash<https://github.com/rails/rails/blob/master/activerecord/lib/active_record/attribute_methods/read.rb#L72> ) - Under Postgres, when attributes have associated OID information i.e.<https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb#L819> In fact as I recall the example I posted above works under Postgres on master, thanks to OID support, but not on sqlite or (presumably) mysql. I tried SQL casts unsuccessfully, though not systematically. There may be plenty more to this picture I'm not aware of, but it seems that there are definite gaps in the picture for DBs other than postgres, and for cases where information isn't understood or available<https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb#L823> . In any case it seems I could look more into establishing the current behavior. Can anyone describe more of the casting picture, apart from the 2 points above? -Ben On Tue, Jul 17, 2012 at 8:53 PM, Jeremy Evans <[email protected]>wrote: > On Tue, Jul 17, 2012 at 8:26 PM, Ken Collins <[email protected]> wrote: > > > > Is this a limitation of PostgreSQL or the ruby library that is used by > said adapter's #raw_connection? Specifically, computed column support? I > know in SQL Server that `MAX(datetime_column)` would return the proper > datatype and the low level connection ruby library, in this case TinyTDS, > would do the legwork before handing things to the adapter then ActiveRecord. > > > > Could the same be achieved doing a CAST() in your SQL string for the > select? > > It's not necessarily a limitation of the PostgreSQL ruby library. pg, > postgres, and postgres-pr all return fields as ruby Strings, but make > the type oid metadata available for all returned fields (doesn't > matter if they are computed fields or not). You shouldn't even need > an SQL cast (as max(timestamp_field) should be of type timestamp), you > just need to know how to map PostgreSQL type oids to ruby classes. > Sequel does this, and I've read that ActiveRecord 4 will as well (and > it looks like it does, see below). > > Maybe what needs to be fixed is replies_topics.written_on is a > timestamptz field, and ActiveRecord currently treats that as a string > instead of a datetime value > ( > https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb#L228 > ) > > Jeremy > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Core" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rubyonrails-core?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-core?hl=en.
