Good catch! Uploading fix in trunk.
Massimo
On Dec 15, 11:13 pm, jonfroehlich <jonfroehl...@gmail.com> wrote:
> Although the web2py documentation (page 165) appears to imply that the
> argument distinct can only be set to True or False, the gluon/sql.py
> file reveals otherwise. From line 2871 of sql.py:
>
> distinct = attributes.get('distinct', False)
> if distinct == True:
> sql_s += ' DISTINCT'
> elif distinct:
> sql_s += ' DISTINCT ON %s' % distinct
>
> So, it appears as though the code is trying to support providing
> specific field names with which to execute the DISTINCT ON expression
> upon (the "elif distinct" part). I found a post about this from June
> when it looks like the above code was first
> proposed:http://groups.google.com/group/web2py/browse_thread/thread/cc6180d335....
> The code, however, does not appear to be executing properly. Whether
> distinct is set to True or, more importantly, whether it is set to a
> field name, the "distinct == True" branch is still taken and the "elif
> distinct" branch is never executed (unfortunately in my case). I could
> be doing something wrong, so let me try to include the relevant
> information.
>
> I have the following table:
> db.define_table('sensor_health',
> Field('deployment_site', 'string'),
> Field('sensor_name', 'string'),
> Field('sensor_started', 'datetime'),
> Field('last_heard_from', 'datetime'),
> Field('sampling_rate', 'double'),
> Field('sensor_event_count', 'integer')
> )
>
> When executing this query:
> sensorHealthRows= db(db.sensor_health.deployment_site ==
> deploymentSite).select(
> db.sensor_health.sensor_name, db.sensor_health.sensor_started,
> db.sensor_health.last_heard_from,
> db.sensor_health.sampling_rate,
> db.sensor_health.sensor_event_count,
> orderby=(db.sensor_health.sensor_name|
> ~db.sensor_health.sensor_started),
> distinct=db.sensor_health.sensor_name)
>
> Which should be equivalent to this in PostgresSQL:
> SELECT DISTINCT ON (sensor_health.sensor_name)
> sensor_health.sensor_name, sensor_health.sensor_started,
> sensor_health.last_heard_from, sensor_health.sampling_rate,
> sensor_health.sensor_event_count
> FROM sensor_health
> ORDER BY sensor_health.sensor_name, sensor_health.sensor_started
> DESC;
>
> I set a breakpoint in sql.py at line 2872 in Wing IDE and the code
> does indeed follow the "distinct == True" branch even though I clearly
> set "distinct = db.sensor_health.sensor_name" in my query. Here's the
> even stranger part: using Wing IDE's Debug Probe, I could actually
> play around with this a bit (a direct copy/paste from the output is
> below). Notice that the type(distinct) is class 'gluon.sql.Field' and,
> perhaps even more interesting, it appears as though distinct evaluates
> to both True and False. What's going on here?
>
> >>> print distinct
>
> sensor_health.sensor_name>>> distinct == True
>
> <gluon.sql.Query object at 0x0393E510>>>> if distinct == True: print
> "distinct is True"
>
> ...
> distinct is True>>> if distinct == False: print "distinct is False"
>
> ...
> distinct is False>>> type(distinct)
>
> <class 'gluon.sql.Field'>
>
> Thanks for your help!
>
> j
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