Decrease score over time

[pandronu (Konrad)]

Hi.

I've got a 'post' index, which has a 'createdAt' date field.

I'm trying to create a query that will return all posts, however, it should apply negative scoring for every day from now to the past.

So, if a post was created today, the scoring would be unaffected, but a post created for example 5 days ago, should have -5 penalty applied. So for every day it would have an extra -1 score applied.

I've tried to achieve this with "linear" decay function but it seems to cover only a very specific date range and I'm rather looking for something more open.

Thanks in advance

[warkolm (Mark Walkom)]

If you shared your existing query it might help someone to offer alternatives or improvements.

[pandronu (Konrad)]

Thanks

Here's the query I have so far:

GET /post/_doc/_search
{
  "explain": false,
  "query": {
    "function_score": {
      "score_mode": "sum",
      "functions": [
        {
            "field_value_factor": {
              "field": "totalVotes"
            },
            "weight": 0.1
        },
        {
            "field_value_factor": {
              "field": "score"
            },
            "weight": 0.05
        },
        {
            "field_value_factor": {
              "field": "totalComments"
            },
            "weight": 0.5
        },
        {
          "filter": {"match": { "hot": true }},
          "weight": 0
        },
        {
          "linear": {
            "createdAt": {
              "scale": "1h",
              "offset": 0,
              "decay": 0.1
            }
          },
          "weight": 100
        }
      ]
    }
  }
}    

Everything apart from the linear function seems to work fine. Just need to find a way to prioritize posts based on their number of days since they're added.