How to perform (sql like) IN queries in aerospike on secondary index. Do we need an UDF for this?
Something like this: Select * from ns.set where si_bin in (1,2,3)
Is there anything available in java aerospike client?
PS: Dont want a range query or that sort.
You can use predicate filtering. https://www.aerospike.com/docs/guide/predicate.html
Python client documentation for predicate filtering has examples for using the aerospike.predexp helper.
The Java client has examples for class PredExp in the repo.
Related
I have a query I wish to run on google Datastore that is intended to retrieve data from multiple devices. However, I couldn't find anywhere in the documentation that would allow me to get data from e.g. device-1 or device-2 or device-3, i.e. only 1 property name can be set. Is this a Datastore limitation? Or am I just missing something that I don't know about?
Based on the NodeJS client library, the query might look something like the below filter criteria:
var query = datastore.createQuery('data')
.filter('device_id', 1)
.filter('device_id', 2)
.filter('device_id', 3);
Otherwise, I might have to run separate queries for the various devices, which doesn't seem like a very elegant solution, especially if there are a lot of devices to simultaneously run queries on.
Any suggestions for the Datastore API or alternative approaches are welcome!
Yes, this would be an OR operation which is one of the Restrictions on queries (emphasis mine):
The nature of the index query mechanism imposes certain restrictions
on what a query can do. Cloud Datastore queries do not support
substring matches, case-insensitive matches, or so-called full-text
search. The NOT, OR, and != operators are not natively
supported, but some client libraries may add support on top of Cloud
Datastore. Additionally:
I am trying to filter rows against a String Type column. Basically I wanted to filter with part of string. It is very similar to LIKE operation in MySQL.
I have gone through this document https://learn.microsoft.com/en-us/rest/api/storageservices/querying-tables-and-entities
However, I couldn't find relevant information for my requirement. Any suggestion more helpful.
Basically I wanted to filter with part of string. It is very similar
to LIKE operation in MySQL.
Azure Tables have limited querying support and unfortunately LIKE is unsupported. What you would need to do is fetch all the entities on the client side and then apply the filter there.
I am looking to write dynamic queries for an ArangoDB graph database and am wondering if there are best practices or standard approaches to doing it.
By 'dynamic queries' I mean that users would have the ability to build a query that is then executed on the dataset.
Methods that ArangoDB can support this could include:
Dynamically generate AQL queries by manually injecting bindvars
Write Foxx functions to deliver on supported queries, and have another Foxx function bind those together to build a response.
Write a workflow which extracts data into a temporary collection and then invokes Foxx functions to filter/sort the data to the desired outcome.
The queries would be very open ended, where someone would (for example):
Query all countries with population over 10,000,000
Sort countries by land in square kilometers
Pick the top 10 countries in land coverage
Select primary language spoken in each country
Count occurrences of each language.
That query alone is straight forward to execute, but if a user was able to [x] check or select from a range of supported query options, order them in their own defined way, and receive the output, it's a little more involved.
Are there some supported or recommended approaches to doing this?
My current approach would be to write blocks of AQL that delivered on each part, probably in a LET Q1 = (....), LET Q2 = (...) format, and then finally in the bottom of the query have a generic way of processing the queries to generate a response.
But I have a feeling that smart use of Foxx functions could help here as well, having Foxx-Query-Q1 and Foxx-Query-Q2 coded to support each query type, then an aggregation Foxx app that invoked the right queries in the right order to build the right response.
If anyone has seen best ways of doing this, it would be great to get some hints/advice.
Thanks!
In SQL, we have an option to specify the LIKE operator in the where clause. Is there something like that in Cassandra? I am building a search feature for my site. All the data resides on Cassandra. So, it would be easier to search for keywords with LIKE operator.
No.You dont have such feature in cassandra. You gotto create a search engine on the data that is stored in cassandra to index the entries in cassandra may be. Cassandra serves as a container to hold your data and does not provide such features like full text search yet(I doubt if they will really as the storage is across SSTables).
If you need search capabilities on cassandra data, look no further than DSE:
http://docs.datastax.com/en/datastax_enterprise/4.7/datastax_enterprise/srch/srchIntro.html
Mongodb doesn't support multi collection query, like "left join" in SQL. It only support "populate", but it can't populate subdocument and find parent-document at the same time.
One line query code in SQL, while mongodb user has to query every parent document _id himself.
I have run into these question:
How to populate other collection's subdocument in mongoose?
https://stackoverflow.com/questions/24075910/mongoose-cant-update-or-insert-subdocuments-array
I finally query every _id by myself in a forEach loop.
Is there a plugin to query multi collection like "join"? Or is there any better solution to multi collection query?
Is there a plugin to query multi collection like "join"?
Some DB products have plug-ins that provide extra features, like PostGIS for Postgres. MongoDB does not have such a plug-in for JOINs. It is unlikely that such a plug-in will ever exist because MongoDB is designed not to have join support.
mongoose...
So the one spot where there is "join-like" support are the drivers. Some drivers and wrappers (like Morphia), have support for opening a document and its related sub-documents from a different collection. However, in this case, the driver/tool is simply doing the work of performing multiple queries on your behalf.
This can easily generate too many queries.
Or is there any better solution to multi collection query?
The only solution provided wholly within MongoDB is going to be via the Map / Reduce or Aggregation Framework tools. Even with these tools, you are likely going to have to do multiple passes of the data and then write some scripts to stitch together this data. This will be a lot of work, but you're trying to do something that MongoDB doesn't like to do, so that's expected.
Another solution would be to leverage Hadoop. MongoDB has a Hadoop plug-in so you can run Hadoop over the existing data. Add in some Hadoop query tools like Hive and then you can get an SQL-Like query over the top. This will also be a lot of work, but will enable to run all sorts of SQL-like queries.