Multi match query or any search query is not working when field data is in Json string format


One of the field in my index is in json string format but I am not able to perform multi match search query on this. For example if I am passing query as my_full_name I am not getting any output. Below is the query which i tried. Can someone help?

GET /_search { "query": { "multi_match": { "query": "my_full_name", "fields": [ "schema.columns" ] } } }

Index data ->
"schema" : { "columns" : "[{\"idx\": 0, \"mode\": \"NULLABLE\", \"name\": \"my_full_name\", \"tags\": null, \"type\": \"STRING\", \"header\": \"my full/name\"}]" }