I have a list of Products with a field called 'Title' and I have been trying to get a list of initial letters with not much luck. The closes I have is the following that dosn't work as 'Distinct' fails to work.
atoz = Product.objects.all().only('title').extra(select={'letter': "UPPER(SUBSTR(title,1,1))"}).distinct('letter')
I must be going wrong somewhere,
I hope someone can help.
You can get it in python after the queryset got in, which is trivial:
products = Project.objects.values_list('title', flat=True).distinct()
atoz = set([i[0] for i in products])
If you are using mysql, I found another answer useful, albeit using sql(django execute sql directly):
SELECT DISTINCT LEFT(title, 1) FROM product;
The best answer I could come up with, which isn't 100% ideal as it requires post processing is this.
atoz = sorted(set(Product.objects.all().extra(select={'letter': "UPPER(SUBSTR(title,1,1))"}).values_list('letter', flat=True)))
Related
I use Django 1.8.17 (I know it's not so young anymore).
I have logged slow requests on PostGres for more than one minute.
I have a lot of trouble finding the Queryset to which the SQL query listed in the logs belongs.
Is there an identifier that could be added to the Queryset to find the associated SQL query in the Logs or a trick to easily identify it?
Here is an exemple of common Queryset almost impossible to identify as I have several similars ones.
Queryset:
Video.objects.filter(status='online').order_by('created')
LOGs:
duration: 1056.540 ms statement: SELECT "video"."id", "video"."title",
"video"."description", "video"."duration", "video"."html_description",
"video"."niche_id", "video"."owner_id", "video"."views",
"video"."rating" FROM "video" WHERE "video"."status" = 'online'
ORDER BY "video"."created"
Desired LOGs:
duration: 1056.540 ms statement: SELECT "video"."id", "video"."title",
"video"."description", "video"."duration", "video"."html_description",
"video"."niche_id", "video"."owner_id", "video"."views",
"video"."rating" FROM "video" WHERE "video"."status" = 'online'
ORDER BY "video"."created" (ID=555)
Add middleware to log a warning when a query takes a long time:
class LongQueryLogMiddleware(object):
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
response = self.get_response(request)
for q in connection.queries:
if float(q['time']) >= settings.LONG_QUERY_TIME_SEC:
logger.warning("Found long query (%s sec): %s", q['time'], q['sql'])
return response
I've made a small gist with all the code. Sorry for the indentation, GitHub keeps removing the indentation.
In the code above I only log the query, but you can add request information that will help you identify where the query comes from.
I don't know Django, so I may be off the mark, but there's a simple trick I heard from one of the people that runs RDS:
Add an identifier to your query as a comment.
So, include a UUID, ID, label, etc. to the query
-- as a comment
and that will flow through to the log. This is an easy way to tie Postgres log entries to specific methods/scripts, it sounds like it would need a bit of adaptation to be useful in your case. (If the idea applies at all.)
I am trying to query a database to obtain rows that matches 4 conditions.
The code I'm using is the following:
$result = db_query("SELECT * FROM transportesgeneral WHERE CiudadOrigen LIKE '$origen%' AND DepartamentoOrigen LIKE '$origendep' AND DepartamentoDestino LIKE '$destinodep' AND CiudadDestino LIKE '$destino%'");
But it is not working; Nevertheless, when I try it using only 3 conditions; ie:
$result = db_query("SELECT * FROM transportesgeneral WHERE CiudadOrigen LIKE '$origen%' AND DepartamentoOrigen LIKE '$origendep' AND DepartamentoDestino LIKE '$destinodep'");
It does work. Any idea what I'm doing wrong? Or is it not possible at all?
Thank you so much for your clarification smozgur.
Apparently this was the problem:
I was trying to query the database by using the word that contained a tittle "Petén" so I changed the database info and replaced that word to the same one without the tittle "Peten" and it worked.
Now, im not sure why it does not accept the tittle but that was the problem.
If you have any ideas on how I can use the tittle, I would appreciate that very much.
I have been messing around with orientdb sql, and I was wondering if there is a way to update an edge of a vertex, together with some data on it.
assuming I have the following data:
Vertex: Person, Room
Edge: Inside (from Person to Room)
something like:
UPDATE Persons SET phone=000000, out_Inside=(
select #rid from Rooms where room_id=5) where person_id=8
obviously, the above does not work. It throws exception:
Error: java.lang.ClassCastException: com.orientechnologies.orient.core.id.ORecordId cannot be cast to com.orientechnologies.orient.core.db.record.ridbag.ORidBag
I tried to look at the sources at github searching for a syntax for bag with 1 item,
but couldn't find any (found %, but that seems to be for serialization no for SQL).
(1) Is there any way to do that then? how do I update a connection? Is there even a way, or am I forced to create a new edge, and delete the old one?
(2) When writing this, it came to my mind that perhaps edges are not the way to go in this case. Perhaps I should use a LINK instead. I have to say i'm not sure when to use which, or what are the implications involved in using any of them. I did found this though:
https://groups.google.com/forum/#!topic/orient-database/xXlNNXHI1UE
comment 3 from the top, of Lvc#, where he says:
"The suggested way is to always create an edge for relationships"
Also, even if I should use a link, please respond to (1). I would be happy to know the answer anyway.
p.s.
In my scenario, a person can only be at one room. This will most likely not change in the future. Obviously, the edge has the advantage that in case I might want to change it (however improbable that may be), it will be very easy.
Solution (partial)
(1) The solution was simply to remove the field selection. Thanks for Lvca for pointing it out!
(2) --Still not sure--
CREATE EDGE and DELETE EDGE commands have this goal: avoid the user to fight with underlying structure.
However if you want to do it (a little "dirty"), try this one:
UPDATE Persons SET phone=000000, out_Inside=(
select from Rooms where room_id=5) where person_id=8
update EDGE Custom_Family_Of_Custom
set survey_status = '%s',
apply_source = '%s'
where #rid in (
select level1_e.#rid from (
MATCH {class: Custom, as: custom, where: (custom_uuid = '%s')}.bothE('Custom_Family_Of_Custom') {as: level1_e} .bothV('Custom') {as: level1_v, where: (custom_uuid = '%s')} return level1_e
)
)
it works well
I make a query via createBuilder() and when executing it (getQuery()->execute()->toArray())
I got 10946 elements. I want to paginate it, so I pass it to:
$paginator = new \Phalcon\Paginator\Adapter\QueryBuilder(array(
"builder" => $builder,
"limit" => $limit,
"page" => $current_page
));
$limit is 25 and $current_page is 1, but when doing:
$paginator->getPaginate();
$page->total_items;
returns 1.
Is that a bug or am I missing something?
UPD: it seems like when counting items it uses created sql with limit. There is no difference what limit is, limit divided by items per page always equals 1. I might be mistaken.
UPD2: Colleague helped me to figure this out, the bug was in the query phalcon produces: count() of the group by counts grouped elements. So a workaround looks like:
$dataCount = $builder->getQuery()->execute()->count();
$page->next = $page->current + 1;
$page->before = $page->current - 1 > 0 ? $page->current - 1 : 1;
$page->total_items = $dataCount;
$page->total_pages = ceil($dataCount / 100);
$page->last = $page->total_pages;
I know this isn't much of an answer but this is most likely to be a bug. Great guys at Phalcon took on a massive job that is too big to do it properly in their little free time and things like PHQL, Volt and other big but non-core components do not receive as much attention as we'd like. Also given that most time in the past 6 months was spent on v2 there are nearly 500 bugs about stuff like that and it's counting. I came across considerable issues in ORM, Volt, Validation and Session, which in the end made me stick to other not as cool but more proven solutions. When v2 comes out I'm sure all attention will on the bug list and testing, until then we are mostly on our own. Given that it's all C right now, only a few enthusiast get involved, with v2 this will also change.
If this is the only problem you are hitting, the best approach is to update your query to get the information you need yourself without getPaginate().
I have this use case where I get the symbolized deep associations from a certain model, and I have to perform certain queries that involve using outer joins. How can one do it WITHOUT resorting to write the full SQL by hand?
Answers I don't want:
- using includes (doesn't solve deep associations very well ( .includes(:cars => [:windows, :engine => [:ignition]..... works unexpectedly ) and I don't want its side-effects)
- writing the SQL myself (sorry, it's 2013, cross-db support, etc etc..., and the objects I fetch are read_only, more side-effects)
I'd like to have an Arel solution. I know that using the arel_table's from the models I can construct SQL expressions, there's also a DSL for the joins, but somehow i cannot use it in the joins method from the model:
car = Car.arel_table
engine = Engine.arel_table
eng_exp = car.join(engine).on(car[:engine_id].eq(engine[:id]))
eng_exp.to_sql #=> GOOD! very nice!
Car.joins(eng_exp) #=> Breaks!!
Why this doesn't work is beyond me. I don't know exactly what is missing. But it's the closest thing to a solution I have now. If somebody could help me completing my example or provide me with a nice work-around or tell me when will Rails include such an obviously necessary feature will have my everlasting gratitude.
This is an old question, but for the benefit of anyone finding it through search engines:
If you want something you can pass into .joins, you can either use .create_join and .create_on:
join_on = car.create_on(car[:engine_id].eq(engine[:id]))
eng_join = car.create_join(engine, join_on, Arel::Nodes::OuterJoin)
Car.joins(eng_join)
OR
use the .join_sources from your constructed join object:
eng_exp = car.join(engine, Arel::Nodes::OuterJoin).on(car[:engine_id].eq(engine[:id]))
Car.joins(eng_exp.join_sources)
I found a blog post that purports to address this problem: http://blog.donwilson.net/2011/11/constructing-a-less-than-simple-query-with-rails-and-arel/
Based on this (and my own testing), the following should work for your situation:
car = Car.arel_table
engine = Engine.arel_table
sql = car.project(car[Arel.star])
.join(engine, Arel::Nodes::OuterJoin).on(car[:engine_id].eq(engine[:id]))
Car.find_by_sql(sql)
If you don't mind adding a dependency and skipping AREL altogether, you could use Ernie Miller's excellent Squeel gem. It would be something like
Car.joins{engine.outer}.where(...)
This would require that the Car model be associated with Engine like so:
belongs_to :engine