Finding your data with views

[colin-jack]

This chapter is excellent but I would rethink this paragraph as you have not described group_level and the rest of the paragraph doesn't seem like it belongs here at the introduction to a new section:

"We use an array key here to support the group_level reduce query parameter. CouchDB’s views are stored in the B-tree file structure (which will be described in more detail later on). Because of the way B-trees are structured, we can cache the intermediate reduce results in the non-leaf nodes of the tree, so reduce queries can be computed along arbitrary key ranges in logarithmic time. See Figure 1, “Comments map function”."

[colin-jack]

The example and description starting from this text could do with a bit of work:

"In the blog app, we use group_level reduce queries to compute the count of comments both on a per-post and total basis, achieved by querying the same view index with different methods. With some array keys, and assuming each key has the value 1:"

[colin-jack]

Worth clarifying what happens when you use multiple startkey values?

"returns the total number of rows between the start and end key. So with startkey=["a","b"]&endkey=["b"](which includes the first three of the above keys) the result would equal 3."

[colin-jack]

I'm not sure how a reader coming to this book to get started learning couchdb is going to be able to interpret this, an example like this without explanation is just confusing. Figure 1 that follows doesnt help either:

"If you’d like to count rows without depending on the row value, you can switch on the rereduce parameter:

function(keys, values, rereduce) { if (rereduce) { return sum(values); } else { return "

[colin-jack]

Pseudocode is fine but showing and explaining the rereducecrelated changes to the reduce would be better:

"The reduce function effectively calculates 3 + 1 on query time and returns the desired result. Example 2, “The result is 4” shows some pseudocode that shows the last invocation of the reduce function with actual values."

[colin-jack]

I felt this chapter was a bit poor around what exactly rereduce was for so I googled and got to the Wiki which explained it clearly. I think that section could perhaps be used as the basis for your content:

http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views

[siddhant3s]

Bingo, I have the same problem with the starting paragraph of ``The view to get comment..." It looks out of line. At least to me, a newbie to couch, I couldn't relate it with the rest of the chapter.

[KevinGaudin]

Ok, so i'm not the only one who is lost on this section. While reading the EPUB version I bought, I thought there was a whole missing chapter there.