Showing posts with label Reference. Show all posts
Showing posts with label Reference. Show all posts

Tuesday, 25 December 2018

MongoDB - Embedding v/s Referencing

MongoDb, a NoSQL document DB, doesn't support the JOIN as RDBMS do which is a very useful feature in DB domain. So what's new or addition in MongoDb which can overcome the JOIN feature. Let's understand this.

First of all, MongoDb is NOT a replacement of standard RDBMS system. It is misconception in DB world that NoSQL DB system will/can replace RDBMS or vice versa. No, It isn't or going to be. Both Database systems have own pros and cons which we will see later.

As the name itself reveals, Embed the data into the document means put all the data together in one document. This will provide a better read performance when you want to get all the related data in one read call as MongoDb stores one document at one place on the disk so minimum seek time is required when reading the data from disk drive.

Let's suppose. we want to create a data model for below ask -

So, Embedding document will look like -

Embedding will cause performance slowness when there are frequent CRUD operations on embedded document. In embedding, data duplication is highly probable. In these cases, we create a document reference rather than document. This is similar to parent-child relationship as we have in RDBMS.

Let's see now how our collection Books will look like -

Next Post on this Series and more on MongoDB can be find here -> LINK

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Monday, 1 February 2016

5 Tips For Better DataStage Design #8

#1. Templates have to be created to enhance reusability and enforce coding standard. Jobs should be created using templates.
#2. The template should contain the standard job flow along with proper naming conventions of components, proper Job level annotation and short/long description. Change record section should be kept in log description to keep track.

#3. Don't copy the job design only. copy using 'save as' or create copy option at the job level.
#4. The DataStage connection should be logged off after completion of work to avoid locked jobs.
#5. Creation of common lookup jobs
#6. Some extraction jobs can be created to created reference datasets. The datasets can then be used in different conversion modules

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