Naive product-centric approach

Finding products on ecommerce website can be tricky, even when you know exactly what you are looking for. This document assumes a customer wants to buy a hammer that weighs 2kg. A product that would meet his needs might be this “Fäustel” by Fortis:

This is (most of) the search-relevant information that is known in the backend of Contorion about the preceding product:

{
  "name": "Fäustel DIN6475 2000g Eschenstiel FORTIS",
  "staple-name": "Fortis Fäustel, mit Eschen-Stiel",
  "description": "Fäustel DIN 6475<br><br>Stahlgeschmiedet, Kopf schwarz lackiert, Bahnen poliert, doppelt geschweifter Eschenstiel mit ozeanblau lackiertem Handende. SP11968 SP11968",
  "preview_image": "faeustel-din6475-2000g-eschenstiel-fortis-21049292-0-JlHR5nOi-l.jpg",
  "categories": [
    "Fäustel",
    "Handwerkzeug",
    "Hammer",
    "Fäustel"
  ],
  "final_gross_price": 1149,
  "final_net_price": 1003,
  "url": "/handwerkzeug/fortis-faeustel-mit-eschen-stiel-SP11968",
  "manufacturer": "Fortis",
  "hammer_weight": 2000
}

Many tutorials recommend storing such documents “as is” in Elasticsearch, and the ease of doing so is indeed one of the core strengths of the platform. However, this approach has at least three quite serious drawbacks:

1. Elasticsearch queries need to “know” and explicitly list all the attributes that they want to use. For example, a full-text search query needs to list all relevant text fields, and a faceted search needs to list all possible filters.
2. Different usages of the same attribute require different handling—for example, the category name “Hammer” needs to be indexed unaltered for filtering and completion but fully analyzed for the full-text search purpose.
3. The existence of “semantic” fields such as hammer_weight makes it hard to extend the product catalog: Whenever new product attributes are created, the Elasticsearch mapping needs to be extended.

The result is huge complexity in query generation and schema management, and this typically leads to situations where the full potential of available data is not used: the full-text search operates only on some fields and faceted navigation on others.