Showing posts with label Performance. Show all posts
Showing posts with label Performance. Show all posts

Monday, 18 February 2019

MongoDB Index in Python - Simple Index


Like RDBMS Systems MongoDB also provide Indexes to improve it's performance to process the query quicker and return the resultset. Mongo supports different type of indexes such as SingleKey, Compound, MultiKey, PartialKey and Text Indexes. We will look into these ones one by one.

Starting with Simple Index or One Key Index which use only one key from the collection/document [quivalent as  Table/Row in RDBMS systems], Let's see how -


Mongo Shell Command:  db.<collectionName>.createIndex({<field>:<direction>})
pyMongo Command:      db.<collectionName>.create_index([(<field>, <direction>)

Let's analyze the impact of Index creation on Query Performance, first via mongo shell, second in python - 

In MongoShell:

In our example, we are taking the collection 'people' as an example which has the field 'last_name'

db.people.find({last_name:'Tucker'}).explain('executionStats')

The above command will generate the executions stats for a query where last_name == Tuker .


as the execution plan shows, mongoDB scanned the whole collection (total 50747 documents for fetching 65 records) to fetch the result which is costly when your collection is big.

Now, Creating a Simple Index or Single Key Index

db.people.createIndex({"last_name":1}) 



Now, querying again the same - 

db.people.find({last_name:'Tucker'}).explain('executionStats')


This time MongoDB finds that there is an Index available on last_name columns which has been used to fetch the result. It scanned only 65 index keys to fetch 65 records. 

Single Key Index can be used in below scenarios - 
   - Querying on the range of Indexed Key values
   - Querying on selected values of Indexed Key

Advantage:
  - Returned result will be sorted by Index Key, no need to put a sort operation if sorting on the index key
  - Index key can be used in any sort order - Ascending or Descending

Consideration while Designing Single Key Index:
  - Do not create Single Key Index on each field available on collections, it will slow down the performance of select and write query both.





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Tuesday, 28 February 2017

ETL Preformance Tuning : Identification of Performance Bottleneck


The goal of performance tuning is to optimize session performance by eliminating performance bottlenecks. To tune the performance of a session, we need to identify a performance bottleneck, eliminate it, and then identify the next performance bottleneck until we are satisfied with the session performance. Test Load option can be used to run sessions while tune session performance.
The most common performance bottleneck occurs when the ETL Server writes to a target database. We can identify performance bottlenecks by the following methods:



Running test sessions. We can configure a test session to read from a flat file source or to write to a flat file target or any stage which can hold the data but not write, to identify source and target bottlenecks.

Studying performance details. We can create a set of information called performance details to identify session bottlenecks. Performance details provide information such as buffer input and output efficiency. Collect Performance Data option in Session Property will enable the Session to generate a Counter of Input and Output rows through each Transformation

Monitoring system performance. System monitoring tools can be used to view percent CPU usage, I/O waits, and paging to identify system bottlenecks.


Once the location of a performance bottleneck is determined, we can eliminate the bottleneck by following these guidelines:

Eliminate source and target database bottlenecks. 
Optimize the query, Increase the database network packet size, or   configuring index and key constraints.

Eliminate mapping bottlenecks. 
Fine tune the pipeline logic and transformation settings and options in  mappings to eliminate mapping bottlenecks.

Eliminate session bottlenecks. 
Session strategy can be optimized performance details can be used to help in tuning session  configuration.

Eliminate system bottlenecks. 
Have the system administrator analyze information from system monitoring tools and improve CPU and network performance.


If all the bottlenecks above are tuned, further optimization of session performance can be done by increasing the number of pipeline partitions in the session. Adding partitions can improve performance by utilizing more of the system hardware while processing the session.




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Thursday, 16 June 2016

5 Tips For Better DataStage Design #14



1. The use of Lookup stage depends upon the volume of data.Sparse lookup type should be used when primary input data volume is small.If the reference data volume is more, Lookup Stage should be avoided.

2. Use of ORDER BY clause in the database is good as compared to use of sort stage.



3. In Dtatastage Administrator, Tuned the 'Project Tunable' for better performance.

4. For Funnel, the use of this stage reduces the performance of a job. Funnel Stage should be run in continuous mode.

5. If the hash file is used only for lookup then "enable Preload to memory". This will improve the performance.






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