Using PowerShell to Simplify your ETL

Scott Weinstein
Principal
Lab49
weblogs.asp.net/sweinstein / @ScottWeinstein
Using PowerShell to simplify your ETL

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SSIS Considered Harmful
Visual programming is a terrible interface for ETL work
History of UI visual designers is instructive here
No way to copy/share “code samples”
Low information density
Even worse
It’s not even a good designer
Poor defaults, poor layout
Nested menus of property grids are hard to use
No real VCS ability
Sure it’s XML, but…
No diff
No merge
Demo ?

But what about all the features?
Some are trivial:
Foreach Loop Container
Execute SQL Task
Send Mail Task
OMG!
Many are useful, but not hard to recreate
Demos soon
Others may be worth consideration
Fuzzy matching

But what about performance
The advantages for data flow are real, but not that large
A 5M row test on my home machine gave a 12% performance advantage to SSIS over PowerShell + SqlBulkCopy

The Answer
PowerShell
A general purpose scripting and automation language
Wide adoption
MS: Windows Server, Windows 7, SQL Server 2008, VM Manager, IIS, Deployment Toolkit
Others: VMWare, Quest, IBM Websphere

PowerShell Features
Takes the best of Unix, VMS, Perl
Adds in integration with .Net, COM, WMI
Adds in
REPL environment
Full scripting/programming
Flexible typing model
Pipes
Regular expressions
XML
Navigation Providers
Built in command parser
Standardized syntax for commands

Introducing PSIS
http://psis.codeplex.com/
Yes, the name is derivative
Right now, just a playground for some demos
Bulk Data Transfer
Star-Schema Populator
Execute SQL

PSIS demo
Just the ETL
No logging, error reporting, etc
Some typical ETL tasks
Clear staging tables
Bulk transfer data from one DB to another
Populate a star schema
Fact table and dimension tables
Extract data to a .csv file

Clear staging tables
Use Invoke-MSSqlCommand
Use Truncate <tablename>

Bulk transfer
At core, we’ll use .Net’sSqlBulkCopy
under the covers uses TDS’s BCP protocol
For concurrency we’ll use the Task Parallel Library
We’ll simplify things by making the destination tables map directly to the source tables
Select statements could provide needed mapping

Populate a Star-Schema
Destination

Source a view on the staging tables, creating a flat de-normalized row of all dimension and fact value
Use convention to indicate which columns are fact or dimension tables

Code generate a populator
Create functions, given a source row which return/create the corresponding dimension key
Run it with the TPL for performance

Areas of improvement
Add support for slowly changing dimensions
Add support for lower memory requirements
query DB for dimension values on demand
Measure and tune performance at the micro-benchmark level
Concurrent dictionaries
Partial loads

Extract to file
Invoke-MSSqlCommand
Export-Csv

Others?

Using PowerShell to Simplify your ETL

by Scott Weinstein

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