rereduce | Reducer library for Redux | State Container library

I'm using PostgreSQL v.11. I have a table with 3 columns. My goal is to find redundancy inside data.

First of all, I do a simple GROUP BY:

I have a pretty simple function that I'm calling in a react.js app that is querying a table on pouchDB and getting the largest value. This was working previously, but it wasn't allowing me to use setState so I changed to arrow function and now inside my then block it tells me it can't get rows of undefined, undefined referring to response

What am I doing wrong, and how can I get this to get response.rows again and setState for my largestActivities value?

I'm trying to solve what seems like a fairly simple problem with a couchDb view, but I'm not even getting close to the target with my result set.

Rather than updating documents, I'm creating a new document every time as my versioning strategy, and tying those documents together with a versioning field called ver. The very first document in a version chain will see the ver field and the _id field having the same value. All subsequent documents in the chain will have the same ver field as previous docs in the chain, but will have a unique _id field. These documents also have a createdTime field which is my way of knowing which document is the latest.

Here's my documents:

In our CouchDB document database, we have documents with different "status" property values like this:

I'm assuming I'm looking at the problem incorrectly, but I seem to be hitting rereduce unexpectedly

A simplified example of my problem would be a student report card

Data (in table format for easy reading)

So assume I have the following two documents in CouchDB:

erlang newbie here. I have a list of lists like

Im trying to do a simple view where it only emits documents where the id begins with "rating-". I dont seem to be able to call any "string:" functions at all in couchdb. Really not sure how to go about this... Every example I've have seen never compares part of value, always the entire value. In ecmascript i'd probably just do if (!doc._id.indexOf('rating-')). In this code below it complains one of the arguments supplied to split is invalid.

I'm trying to write a query in CouchDB that will get names and ages of all people who have the maximum age, grouping by gender and isActive status. There is only one data document being searched. As an intermediate step to understanding how to write the reduce function when the values are objects, I've written a query that just returns the maximum age within each group, but this has been unsuccessful. The following map and reduce functions return the appropriate keys, which are the 4 combinations of male/female and true/false, but the values always come back 0 in all four groups.

Why does this view not return the maximum age for each group?

Map Function: