Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Querying attachments

From: Up and Running with NoSQL Databases

Video: Querying attachments

Once attachments have been uploaded to your CouchDB database, you'll want to be able to reference them easily. Let's create a view to help us get all of the attachment names. First, let's navigate to the restaurant database. Then head over to the View dropdown, and select Temporary View. If you have the default function that just emits null on the document, click Run. Now, let's narrow that down to the Attachments field, add in a dot, and then underscore, and then attachments.

Querying attachments

Once attachments have been uploaded to your CouchDB database, you'll want to be able to reference them easily. Let's create a view to help us get all of the attachment names. First, let's navigate to the restaurant database. Then head over to the View dropdown, and select Temporary View. If you have the default function that just emits null on the document, click Run. Now, let's narrow that down to the Attachments field, add in a dot, and then underscore, and then attachments.

You'll notice that some of our documents don't have an attachments field, while the other ones do. We want to have a function that only returns the documents that have attachments. So let's go to the exercise files and get one. Open up map.js and copy the function. Then paste that function over the existing map function. The ultimate goal here is to get one file name per document.

This function is a little bit complicated, so let's step through it. First, we are detecting whether or not the document has an attachments field. If it doesn't have an attachments field, we just skip over it. First, we're going to get one file name for each document, and then emit the name field for the document as the key and the file name as the value. To actually get that file name, we have a very complicated looking loop. We are using JavaScript's for-in construct to get the object properties of the attachments field.

This gives us each of the property names as a key. And then we run two tests on this key. First, we want to make sure that this key actually belongs to this attachments object, and then we want to make sure this key does not actually point to a function. In JavaScript, we are not guaranteed the ordering of the object properties. So we use these checks to make sure that we just get the file name. Once we have that file name, we stop the loop and emit. Now let's click the Run button.

This view has everything we need. We have the document name as the key, and the file name as the value. We also have the document ID handy. This will help us construct the URLs we need to point to the images. Now, let's click Save As so we can save this view. For the design document, type menu, and for the view name type items. So now we have this as a permanent view in our system. We can also view the raw data. Remove everything from the question mark down to the root.

So now we have that same data available in JSON format. Creating a view is helpful for getting a clean list of attachment file names. With this view in place, you can now easily build applications based around it.

Show transcript

This video is part of

Image for Up and Running with NoSQL Databases
Up and Running with NoSQL Databases

29 video lessons · 12273 viewers

Joseph LeBlanc
Author

 

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ .

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Up and Running with NoSQL Databases.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member ?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferences from the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.