HW 3 – Document data stores. MongoDB

(5 points)

  1. Design the data structures based on the analytical tasks (see HW1) that are intended to be solved with MongoDB.
    • The structures must be designed so that the target queries are feasible.
    • Avoid overly nested documents.
      • Denormalize only when it benefits performance; do not create overly deep nesting that complicates queries.
  2. Insert the data into MongoDB using the CSV/JSON generated for the project (see HW0). Use the Base dataset as defined in HW0.
    • Load only what is needed for tasks/comparisons. Do not import unnecessary data.
  3. Implement and run the queries (see HW1). Create supporting indexes for every analytical query.
    • Use the Aggregation Pipeline; do not use `$where`, server-side JavaScript, or `mapReduce`.
    • Apply appropriate time filters, groupings, and KPIs as required by your HW1 tasks (do not hardcode specific fields like “country/action” if your domain differs).
    • For each query, include `db.collection.explain(“executionStats”).aggregate(…)` (or the relevant command) and show a compact excerpt of the plan in the report.
  4. Prepare a report and include:
    • the text from HW0 and HW1 (edited if necessary);
    • the collections creation and document-insertion commands, with explanations of why this structure was chosen;
    • the data import code;
    • the queries used to solve the analytical tasks. For each task, provide:
      • the task number (as in the previous work);
      • the verbal description of the task;
      • the query code with explanations;
      • a screenshot (or excerpt) of the query result and the `explain(“executionStats”)` output.

Note. If some analytical tasks turn out to be infeasible or meaningless, you may replace them with others and propagate the corresponding changes to the earlier work (HW0/HW1).

Submit to the BRUTE system:

Submit to the NoSQL server (nosql.felk.cvut.cz) the hw3.js file with MongoDB commands with short comments. 

mongosh --port 42222 -u login -p password database hw3.js