We recently switched from MongoDB to TokuMX. In one collection our documents all have a numerical filed, "docType". Some documents have a field "DL_Number", and others don't. For those documents with a "DL_Number" field, the combination of "docType" and "DL_Number" should serve as a unique index.
Using C++ Legacy, we originally created an index like this:
mongo::IndexSpec().addKey("docType").addKey("DL_Number").unique().partialFilterExpression(BSON("DL_Number" << BSON("$exists" << true)));
What we were going for was an index where "docType" and "DL_Number" would provide a unique key for documents that had a field "DL_Number".
The statement worked find in MongoDB, but now that we've switched to TokuMX, the partial filter doesn't work any more. Trying to insert the second document without a "DL_Number" field throws an exception.
Has anybody else had this problem with TokuMX? Were you able to find a work-around?
Partial indexes are a MongoDB 3.2 feature, but TokuMX is based on MongoDB 3.0, so this MongoDB feature is not available with TokuMX.
Related
My Django JSON field contains a list of values like ["N05BB01", "R06AX33"].
atc_code = JSONField(default=list())
I would like to filter this field, for 'does any string in list contain "N05"?'.
like
mymodel.objects.filter(?????)
In this case if you are not using SQLite or Oracle, you can use contains:
mymodel.objects.filter(atc_code__contains='N05')
Which generates this SQL:
SELECT * FROM "mymodel" WHERE UPPER("mymodel"."atc_code"::text) LIKE UPPER(%N05%)
Relational-based answer
Usually, such an approach (with a list of values in JSONField) can be possible when the relational structure is used in the wrong way.
The best approach here:
Create a new model that describes your atc_code entity. For example AtcCode
Depends on the meaning of the atc_code and its relation to the MainEnity use ForeignKeyField or ManyToManyField
Utilize all pros from the relational database and powerful Django ORM with such built-in features as filtering, adding, removing, querying with any database backend.
It will work on any supported database. A relational database will work faster when you are using relations properly.
My recommendation is to use JSONField when you have a really unstructured object.
I am writing a simple app in django that searches for records in database.
Users inputs a name in the search field and that query is used to filter records using a particular field like -
Result = Users.objects.filter(name__icontains=query_from_searchbox)
E.g. -
Database consists of names- Shiv, Shivam, Shivendra, Kashiva, Varun... etc.
A search query 'shiv' returns records in following order-
Kahiva, Shivam, Shiv and Shivendra
Ordered by primary key.
My question is how can i achieve the order -
Shiv, Shivam, Shivendra and Kashiva.
I mean the most relevant first then lesser relevant result.
It's not possible to do that with standard Django as that type of thing is outside the scope & specific to a search app.
When you're interacting with the ORM consider what you're actually doing with the database - it's all just SQL queries.
If you wanted to rearrange the results you'd have to manipulate the queryset, check exact matches, then use regular expressions to check for partial matches.
Search isn't really the kind of thing that is best suited to the ORM however, so you may which to consider looking at specific search applications. They will usually maintain an index, which avoids database hits and may also offer a percentage match ordering like you're looking for.
A good place to start may be with Haystack
Can Django support Oracle nested tables or varrays or collections in some manner? Asking just for completeness as our project is reworking the data model, attempting to move away from EAV organization, but I don't like creating a bucket load of dependent supporting tables for each main entity.
e.g.
(not the proper Oracle syntax, but gets the idea across)
Events
eventid
report_id
result_tuple (result_type_id, result_value)
anomaly_tuple(anomaly_type_id, anomaly_value)
contributing_factors_tuple(cf_type_id, cf_value)
etc,
where the can be multiple rows of the tuples for one eventid
each of these tuples can, of course exist as separate tables, but this seems to be more concise. If it 's something Django can't do, or I can't modify the model classes to do easily, then perhaps just having django create the extra tables is the way to go.
--edit--
I note that django-hstore is doing something very similar to what I want to do, but using postgresql's hstore capability. Maybe I can branch off of that for an Oracle nested table implementation. I dunno...I'm pretty new to python and django, so my reach may exceed my grasp in this case.
Querying a nested table gives you a cursor to traverse the tuples, one member of which is yet another cursor, so you can get the rows from the nested table.
I posted a similar question over on the Adobe Community forums, but it was suggested to ask over here as well.
I'm trying to cache distinct queries associated with a particular database, and need to be able to flush all of the queries for that database while leaving other cached queries intact. So I figured I'd take advantage of ColdFusion's ehcache capabilities. I created a specific cache region to use for queries from this particular database, so I can use cacheRemoveAll(myRegionName) to flush those stored queries.
Since I need each distinct query to be cached and retrievable easily, I figured I'd hash the query parameters into a unique string that I would use for the cache key for each query. Here's the approach I've tried so far:
Create a Struct containing key value pairs of the parameters (parameter name, parameter value).
Convert the Struct to a String using SerializeJSON().
Hash the String using Hash().
Does this approach make sense? I'm wondering how others have approached cache key generation. Also, is the "MD5" algorithm adequate for this purpose, and will it guarantee unique key generation, or do I need to use "SHA"?
UPDATE: use cacheRegion attribute introduced in CF10!
http://help.adobe.com/en_US/ColdFusion/10.0/CFMLRef/WSc3ff6d0ea77859461172e0811cbec22c24-7fae.html
Then all you need to do is to specify cachedAfter or cachedWithin, and forget about how to to generate unique keys. CF will do it for you by 'hashing':
query "Name"
SQL statement
Datasource
Username and
password
DBTYPE
reference: http://www.coldfusionmuse.com/index.cfm/2010/9/19/safe.caching
I think this would be the easiest, unless you really need to fetch a specific query by a key, then u can feed your own hash using cacheID, another new attribute introduced in CF10.
I have a simple database and want to update an int value. I initially do a query and get back a ResultSet (sql::ResultSet). For each of the entries in the result set I want to modify a value that is in one particular column of a table, then write it back out to the database/update that entry in that row.
It is not clear to me based on the documentation how to do that. I keep seeing "Insert" statements along with updates - but I don't think that is what I want - I want to keep most of the row of data intact - just update one column.
Can someone point me to some sample code or other clear reference/resource?
EDIT:
Alternatively, is there a way to tell the database to update a particular field (row/col) to increment an int value by some value?
EDIT:
So what is the typical way that people use MySQL from C++? Use the C api or the mysql++? I guess I chose the wrong API...
From a quick scan of the docs it appears Connector/C++ is a partial implementation of the Java JDBC API for C++. I didn't find any reference to updateable result sets so this might not be possible. In Java JDBC the ResultSet interface includes support for updating the current row if the statement was created with ResultSet.CONCUR_UPDATABLE concurrency.
You should investigate whether Connector/C++ supports updateable resultsets.
EDIT: To update a row you will need to use a PreparedStatement containing an SQL UPDATE, and then the statement's executeUpdate() method. With this approach you must identify the record to be update with a WHERE clause. For example
update users set userName='John Doe' where userID=?
Then you would create a PreparedStatement, set the parameter value, and then executeUpdate().