Introduction

This week I want to discuss the trouble you may have when searching hundreds of zip files for specific files inside them.
Recognizable?
At least I faced this problem some time ago, and solved it using SSIS and the commandline version of 7-zip, named 7za.exe.
The choice for SSIS was purely based on convenience, as you could tackle this problem also using Powershell, C# or almost any other scripting language.
But I thought SSIS is just a neat and quick way to do this.

Problem

Finding specific files in huge amounts of zip files.

Solution

To tackle this problem I have made a fully configurable SSIS package, that can be executed with different parameters.
The main task of the package is to extract specific files (based on a file name pattern) from zipfiles in a folder and – optionally – subfolders.
The unzipping itself is done with 7za.exe, which is the commandline version of 7z, the great open source zip program, that exists already for several years and is used by millions of users.

By the way, the package is made using SSIS 2014.

Preparations: download and install 7za

It is important to download this package from the official 7z web site, just to avoid that you would get a copy from some deceitful web site infected with malware.
To go to the official 7-zip download page click on this link:
7-zip download page
Most important is the 7-Zip Extra: standalone console version.
For the example I have used version 16.02 (2016-05-21) for Windows, but it should also work with version 9.20 (2010-11-18), then called 7-Zip Command Line Version.

If you download the newest version, you also need software to unzip the 7z160-extra.7z file, for instance the regular 32-bit or 64-bit version of 7-zip, which can also be downloaded on the same page.

Download page of 7-zip

I assume you will use the newest version 7z160-extra.7z
Once unzipped, just take the time to read License.txt, readme.txt and history.txt.
Then copy the three files 7zxa.dll, 7za.dll and 7za.exe to a folder on the Windows computer where SSIS runs, usually a Windows Server.
If you run a x64 version of Windows, you can take the x64 version of the 7za files, which are in a subfolder “x64” of the unzipped files.

Unzipped 7za files ..

I have created a subfolder “7za” in the “C:\Program files” folder of my virtual Windows Server, and copied the x64-version of the three mentioned files to it, but you can put them in any folder you like.
When you have done this, the real fun can start ..

Overview

Here is a picture of the end result:

The Control Flow

Detailed steps

Parameters and variables

First you need to add a few parameters and variables to the package.

Parameters:

Package parameters

Variables:

SSIS variables needed to do the job

Developing the package

FELC Unzip files

This foreach loop container finds all zip files.
In the Foreach Loop Editor, select Collection in the left pane.
As we want to make the solution generic by using all those parameters mentioned above, we have to add a few expressions.

Foreach Loop container Collection configuration

Add the following three expressions (in my opinion the editor is not very userfriendly, the window is too small, but it can be done):

Please note that these expressions will set the values for Folder, Files and the Traverse subfolders checkbox in the Enumerator configuration part of the screen (inside the purple square in the picture above).
If you close and reopen the Foreach Loop Editor, you will notice that the configuration fields now use the values from the corresponding parameters, except the value Fully qualified for Retrieve file name, which is hardcoded.

Example of how to set an expression..

Then, still in the Foreach Loop Editor, select Variable Mappings in the left pane and map variable User::FLC_ZipPathAndFileName to Index 0, as shown in the picture below.

Variable Mappings

EXPR Set Unzip folder

The next nifty thing that needs to be done, is creating a folder to store the unzipped files. As we do not know if zipped files with the same name exist in multiple zip files, the safest thing to do is to create a directory structure identical to the directory structure of the zip files.
Additionally, the basename of the zip file (so without file extension) is used as an extra subfolder. In this way we are sure that unzipped files with the same name can be stored without overwriting other ones.

To do this, from the SSIS Toolbox drag an Expression Task inside the Foreach Loop container.
Open the Expression Task and paste this expression into the Expression textbox.

Then press the Evaluate Expression button to check that the expression is valid.

Configuring the Expression Task

FSYS Create Unzip folder

In the previous step we have composed the full path to unzip files into, but this folder structure might not exist yet.
Therefore we use A File System Task named FSYS Create Unzip folder to create the folder structure.
The good news is that the File System Task can create multiple (sub)folders at once.
Configure it as shown in the picture.

Configuration of FSYS Create Unzip folder

EPR Unzip Selected Files

Below you see a few screenshots for the configuration of the Execute Process Task named EPR Unzip Selected Files.
The funny thing is, that in the Process pane, you do not have to change anything. Executable and Arguments are set using expressions (coming next) and all the other properties can keep their default values.

Process configuration.

Setting Executable and Arguments using expressions
Arguments (copy-friendly):

SCR Remove Empty folders

There is one problem with the steps done so far. If a zipfile does not contain a file that matches the FilenamePattern, then the folderstructure is made for nothing.
However you could just leave these empty folders, I think the solution is a bit better if these empty folders are deleted.
To do this, from the SSIS Toolbox drag an Script Task inside the Foreach Loop container.

In the Script Task Editor, add both variables User::FLC_UnzipFolder and $Package::UnzipRootFolder to ReadOnlyVariables

In the Script Task Editor window, press Edit Script ….

Please note that you can download the C# script here..

Then in the namespaces region add two namespaces, as indicated below.

Adjust public void main() as follows:

Download the script here.

The proof of the pudding is in the eating

Time to do some testing.
I have created a few folders with subfolders and subsubfolders. You can see the folder structure in the last picture below.
As you might have noticed the default values for my parameters already prepared for the testcase: I want to unzip only customer files from zip files with 201605 in the name.

Executing the package in Debug mode..

Below you can see the result. Only customer files are unzipped. The subfolders under the Archive folder that contain no customer zip files (but only currency files), do not exist under the Unzipped folder.

Folder structure of Archive and Unzipped rootfolders..

Unzipped “Customer” files ..

Important notes for using with huge amounts of zip files

From my experience I must also warn you. If you run this package on a folder containing gigabytes of zipfiles, there are two things to be aware of:

1. The execution of the package can potentially take a long time, several hours is not unusual.
2. Make sure you have enough disk space. Suppose you have the following hypothetical scenario: zip files: 100GB, average zip compression rate: 20%, percentage of files to be unzipped: 30%. In this case you are going to unzip files that have a zipped size of 30% of 100GB, is 30GB. Once unzipped, their size will be 30GB * (1/0,20) = 150GB. You need to have that disk space available on the disk where the Unzipped folder resides.

Conclusion / Wrap up

With this SSIS package you can selectively unzip files from archived zip files.
When using it, make sure you have enough disk space, and be aware that the package can run for several hours, depending on the number and (average) size of the zip files to process.

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