nosql
Why isn’t RDBMS Partition Tolerant in CAP Theorem and why is it Available?
It is very easy to misunderstand the CAP properties, hence I’m providing some illustrations to make it easier. Consistency: A query Q will produce the same answer A regardless the node that handles the request. In order to guarantee full consistency we need to ensure that all nodes agree on the same value at all … Read more
NoSQL Use Case Scenarios or WHEN to use NoSQL [closed]
It really is an “it depends” kinda question. Some general points: NoSQL is typically good for unstructured/”schemaless” data – usually, you don’t need to explicitly define your schema up front and can just include new fields without any ceremony NoSQL typically favours a denormalised schema due to no support for JOINs per the RDBMS world. … Read more
When to Redis? When to MongoDB? [closed]
I would say, it depends on kind of dev team you are and your application needs. For example, if you require a lot of querying, that mostly means it would be more work for your developers to use Redis, where your data might be stored in variety of specialized data structures, customized for each type … Read more
MAX(), DISTINCT and group by in Cassandra
With Cassandra you solve these kinds of problems by doing more work when you insert your data — which sounds like it would be slow, but Cassandra is designed for fast writes, and you’re probably going to read the data many more times than you write it so it makes sense when you consider the … Read more
How to make a query date in mongodb using pymongo?
@Joni is correct, you need to use datetime. from datetime import datetime from pymongo import Connection # i have updated and included the complete code client = Connection(‘localhost’, 27017) db = client[‘database’] # your database name inoshare = db[‘inoshare’] # convert your date string to datetime object start = datetime(2014, 9, 24, 7, 51, 04) … Read more
MongoDB nested array query
After running some queries, I came to the conclusion that $in doesn’t work for an array of arrays. You can use $elemMatch instead and it’ll work, but it is frustrating that MongoDB’s documentation doesn’t warn about it. I created this document: { “_id”: “51cb12857124a215940cf2d4”, “level1”: [ [ “item00”, “item01” ], [ “item10”, “item11” ] ], … Read more
Fast or Bulk Upsert in pymongo
Modern releases of pymongo ( greater than 3.x ) wrap bulk operations in a consistent interface that downgrades where the server release does not support bulk operations. This is now consistent in MongoDB officially supported drivers. So the preferred method for coding is to use bulk_write() instead, where you use an UpdateOne other other appropriate … Read more
Mongodb: Failed to connect to 127.0.0.1:27017, reason: errno:10061
This is how I solved it, You can follow step by step here: MongoDB Steps: Download the latest 64-bit MSI version of MongoDB for Windows. Run the installer (.msi file) Add it to your PATH of environment variables. it Should be from: C:\Program Files\MongoDB\Server\3.0\bin now Create a “\data\db” folder in C:/ which is used by … Read more