Logstash filter query with if else

Question

I am facing issues with Logstash filters: I want to put a condition like following:

filter {
       if [SPCI] == 79 {
            mutate {
                 replace => { "RSRP79" => "%{SRSRP}" }
                 replace => { "RSRQ79" => "%{SRSRQ}" }
                   }
       }

My dataset looks like:

{
  "took": 29,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 22656,
    "max_score": null,
    "hits": [
      {
        "_index": "processed.radiosignal",
        "_type": "_doc",
        "_id": "v_FJQnYBEKhQVcwaCsCy",
        "_version": 26,
        "_score": null,
        "_source": {
          "ElapsedRT": 0,
          "Alt": 0,
          "Row": 0,
          "RSRP116": "0",
          "NRSRP": -103,
          "@version": "1",
          "Handover": 0,
          "Time": "2020.12.08-11.34.49.14",
          "NRSRQ": -13,
          "SPCI": 79,
          "SRSRP": -100,
          "@timestamp": "2020-12-15T17:31:29.080Z",
          "SRSRQ": -11,
          "RSRP79": "0",
          "NPLMN": "nullnull",
          "NPCI": 116,
          "RSRQ116": "0",
          "Lat": 0,
          "Long": 0,
          "RSRQ79": "0"
        },
        "fields": {
          "@timestamp": [
            "2020-12-15T17:31:29.080Z"
          ]
        },
        "sort": [
          1608053489080
        ]
      }

The query is not performing as expected and if SRSRP == 79 is failing. I am quite new to ELK and could not understand where is the issue. Just to clarify, I am creating RSRP79 and RSRQ79 fields using alter plugin in previous step and it is working fine.