I am new to cassandra (started learning on my own interest few days back) and looking for help for the below problem.
I have a Cassandra table "User" and a ListColumn "interests extends ListColumn[String]".
Now, I want to fetch all users with an interest, say "playing".
like: select from user where interests.contains("playing")!
I scanned through the ListColumn api but not able to find any. Also, searched in google but no such helpful posts.
Any help guys please... Thanks in Advance :)
So there is contains among operators and here is an example how to use it. It looks like that it should work as any other operator, so just go for database.userTable.select.where(_.interests contains "playing").fetch() - of course, depending on your conventions.
This is possible with a secondary index on a collection column, which only works with a Set column, and not with a List.
Bottom line:
object interests extends SetColumn[String](this) with Index[Set[String]]
And then you can execute the following:
select.where(_.interests contains "test").fetch()
You can also use multiple restrictions if you allow filtering.
select.where(_.interests contains "test")
.and(_.interests contains "test2")
.allowFiltering()
.fetch()
The above will only match if both interests are found in a record.
Related
Please refer My previous question .
With respect to the this answer for my question, I could do with one filed.
I Could not able to do with multiple fields.
http://$solr_host:8983/solr/magazines/select&q=sport+education&df=title&q.op=OR - this is working for one field. How can I do it for multiple field.
What is the right way to achieve my objective. Thank you in advance.
Use Dismax/eDismax with qf (Query Fields) Parameter.
example:
http://$solr_host:8983/solr/magazines/select&q=sport+education&defType=edismax&qf=title name&q.op=OR
Check this here
Supposing I have a model Post, wich contains only the field desc.
The user can use hashtags, like #rails inside any posts...
How can I list and count the hashtags used, for example, in the last 10 days?
I'm do not know much about mongodb, but I see that I could use something called map_reduce.. have no idea why/how.
Thanks in advance.
You are right...this can be solved using mad/reduce function...
try this or this gem if you dont want to think a lot lol
https://github.com/jcoene/mongoid-mapreduce
How can I write a query with ormlite instead of using .create or any other thing like that? Can you please show me how for this simple example :
SELECT name FROM client
EDIT since I can't answer myself :
I guess I had to search a little more , anyway I found how to do it with the QueryBuilder like this :
newDao.query(newDao.queryBuilder().where.eq("name",valueofname)
If someone knows how to write the full query that would be great , otherwise , I'll stick with this solution
How can I write a query with ormlite instead of using .create or any other thing like that?
Goodness, there are tons of documentation about how to do this on the ORMLite site. Here's the section on the query builder.
I'm not sure what you mean by "full query" but your example will work with some tweaks:
List<...> results = newDao.queryBuilder().where().eq("name",valueofname).query();
It does not make sense to just return the name since the Dao hierarchy is designed to return the specific Client object. If you just want the name the you can specify the name column only to return:
... clientDao.queryBuilder().selectColumns("name").where()...
That will return a list of Client objects with just the name field (and the id field if it exists) extracted from the database.
If you just want the name strings then you can use the RawResults feature.
I have a large table which inserts data into the database. The problem is when the user edits the table I have to:
run the query
use lots of lines like value="<cfoutput>getData.firstname#</cfoutput> in the input boxes.
Is there a way to bind the form input boxes to the database via a cfc or cfm file?
Many Thanks,
R
Query objects include the columnList, which is a comma-delimited list of returned columns.
If security and readability aren't an issue, you can always loop over this. However, it basically removes your opportunity to do things like locking certain columns, reduces your ability to do any validation, and means you either just label the form boxes with the column names or you find a way to store labels for each column.
You can then do an insert/update/whatever with them.
I don't recommend this, as it would be nearly impossible to secure, but it might get you where you are going.
If you are using CF 9 you can use the ORM (Object Relation Management) functionality (via CFCs)
as described in this online chapter
https://www.packtpub.com/sites/default/files/0249-chapter-4-ORM-Database-Interaction.pdf
(starting on page 6 of the pdf)
Take a look at <cfgrid>, it will be the easiest if you're editing table and it can fire 1 update per row.
For security against XSS, you should use <input value="#xmlFormat(getData.firstname)#">, minimize # of <cfoutput> tags. XmlFormat() not needed if you use <cfinput>.
If you are looking for an easy way to not have to specify all the column names in the insert query cfinsert will try to map all the form names you submit to the database column names.
http://help.adobe.com/en_US/ColdFusion/9.0/CFMLRef/WSc3ff6d0ea77859461172e0811cbec22c24-7c78.html
This is indeed a very good question. I have no doubt that the answers given so far are helpful. I was faced with the same problem, only my table does not have that many fields though.
Per the docs EntityNew() the syntax shows that you can include the data when instantiating the object:
artistObj = entityNew("Artists",{FirstName="Tom",LastName="Ron"});
instead of having to instantiate and then add the data field by field. In my case all I had to do is:
artistObj = entityNew( "Artists", FORM );
EntitySave( artistObj );
ORMFlush();
NOTE
It does appear from your question that you may be running insert or update queries. When using ORM you do not need to do that. But I may be mistaken.
i am wondering how can i select specific number of child objects instead of taking them all with include?
lets say i have object 'Group' and i need to select last ten students that joined the group.
When i use '.Include("Students"), EF includes all students. I was trying to use Take(10), but i am pretty new to EF and programming as well, so i couldn't figure it out.
Any suggestions?
UPDATED:
ok, i have Group object already retrieved from db like this:
Group group = db.Groups.FirstOrDefault(x=>x.GroupId == id)
I know that i can add Include("Students") statement, but that would bring ALL students, and their number could be quite big whether i need only freshest 10 students. Can i do something like this: var groupWithStudents = group.Students.OrderByDescending(//...).Take(10);?
The problem with this is that Take<> no longer appears in intellisense. Is this clear enough? Thanks for responses
I believe Take(10) would be correct.
var Students= (from c in Groups
orderby c.DateAdded descending
select c).Take(10);
My experience with Take though is that it generates some awful sql.
EDIT:
see if this blog post helps, it talks of conditional includes.
http://blogs.msdn.com/b/alexj/archive/2009/10/13/tip-37-how-to-do-a-conditional-include.aspx
Couldn't make Gratzy's suggestion with conditional include work... and found the solution here: http://msdn.microsoft.com/en-us/library/bb896249.aspx
Query would look like this:
group.Students.Attach(group.Students
.CreateSourceQuery()
.OrderByDescending(x=>x.JoinDate)
.Take(10));
This is exactly what i was looking for!
Thanks for all responses anyway!