The docs don't mention it, but you can force an INNER JOIN by using the
string-style association syntax:
TranslationTarget.first('translation_key.source' => source)
http://stackoverflow.com/a/6716151/215168
On Thu, May 1, 2014 at 6:42 PM, Charley Kline <cvkl...@gmail.com> wrote:
> I'm responding far after the original post, but...
>
> I suspect it is a universal property of ORMs that they will not usually be
> able to construct an SQL query that is as efficient as what someone could
> write by hand. I have seen similar cases to yours where DataMapper just
> didn't have enough information to connect the dots to build a single query
> that joined several tables, and instead made an initial query to pull
> records out of one table, and then generated a second query that included
> something like "... WHERE other_table_id IN (3,6,10,17,24,31,35,38,40)."
> It makes old RDBMS people cringe, to be sure, but using an ORM is not
> about generating optimal SQL.
>
> We ignore these inefficiencies because of the way that an ORM allows us to
> manipulate related data objects in the natural way of the language we're
> writing in. Also, if the relevant objects have already been loaded into the
> application using DataMapper, it is often the case that the underlying
> relational database doesn't need to get called at all.
>
> /cvk
>
>
>
> On Monday, May 6, 2013 5:57:50 PM UTC-5, Tiago Matos wrote:
>>
>> Hello,
>>
>> I have a performance related question.
>>
>> We have a call which runs multiple times per page load. After reading
>> http://datamapper.org/docs/associations.html we currently have
>> TranslationTarget.first(:translation_key => {:source => source}) but it
>> first does a query to table TranslationKey then the query
>> to TranslationTarget:
>>
>> DEBUG - (0.000468) SELECT `id` FROM `translation_keys` WHERE (`source` =
>> 'Top Referrers' AND `domain` = 'admin')
>> DEBUG - (0.002409) SELECT `id`, `revision_status`,
>> `revision_account_email`, `locale`, `updated_at`, `translation_key_id`,
>> `account_id` FROM `translation_targets` WHERE (`translation_key_id` = 369
>> AND `locale` = 'pt' AND `revision_status` = 'approved') ORDER BY `id` LIMIT 1
>>
>> *(domain and revision_status are not very important fields, just filters)*
>>
>> Is there a way to use Datamapper here and avoid direct SQL?
>>
>> Many thanks in advance.
>>
>> Tiago Duarte Matos
>> http://tiagomatos.org
>>
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