Adding new fields to doc_mapping unexpectedly alters tag_fields behavior

Describe the bug
When adding new fields to the doc_mapping configuration, it causes unexpected changes in the values retrieved from fields defined in tag_fields.

For example:

In the current index configuration (version 0.9, index_id: spot-trade-etl_exlogs), we have tag_fields: [app_name]properly defined. However, after adding the 'uri' field to field_mappings, the way tag content is processed changes unexpectedly.

​Current Behavior
Modifying doc_mapping (such as adding the uri field) inadvertently affects the retrieval mechanism of fields marked in tag_fields (app_name in this case), producing unexpected values.

Expected behavior

1. tag_fields values should remain stable
2. Schema modifications (add/remove fields) should not impact existing tag_fields

Configuration:

version: 0.9
index_id: spot-trade-etl_exlogs
doc_mapping:
  mode: dynamic
  dynamic_mapping:
  field_mappings:
    - name: "@timestamp"
      type: datetime
      input_formats:
        - iso8601
        - "%Y-%m-%d %H:%M:%S.%f"
      output_format: "%Y-%m-%d %H:%M:%S.%f"
      fast: true
      fast_precision: microseconds
    - name: time
      type: datetime
      input_formats:
        - "%Y-%m-%d %H:%M:%S.%f"
        - iso8601
      output_format: "%Y-%m-%d %H:%M:%S.%f"
      fast: true
      fast_precision: milliseconds
    - name: level
      type: text
      fast: true
    - name: msg
      type: text
      tokenizer: chinese_compatible
      record: position
      fieldnorms: true
      fast:
        normalizer: lowercase
    - name: log
      type: text
      tokenizer: chinese_compatible
      record: position
      fieldnorms: true
      fast:
        normalizer: lowercase
    - name: tid
      type: text
      tokenizer: raw
      fast: true
      stored: true
      record: basic
    - name: biz_monitor_ctx
      type: text
      record: position
    - name: uri
      type: text
      record: position
    - name: event
      type: text
      fast: true
      record: position
    - name: app_name
      type: text
      tokenizer: raw
      fast: true
    - name: namespace
      type: text
      fast: true
      tokenizer: raw
    - name: pod_name
      type: text
      fast: true
      record: position
    - name: node_name
      type: text
      fast: true
      tokenizer: raw
  timestamp_field: "@timestamp"
  tag_fields: [app_name]
search_settings:
  default_search_fields: [app_name, pod_name]
indexing_settings:
  commit_timeout_secs: 30
  merge_policy:
    type: "stable_log"
    min_level_num_docs: 100000
    merge_factor: 10
    max_merge_factor: 12
retention:
  period: 15 day
  schedule: hourly

{
    "split_state": "MarkedForDeletion",
    "update_timestamp": 1755676264,
    "publish_timestamp": 1755676264,
    "version": "0.9",
    "split_id": "01K3379N8EMHT3MYJ4WD9VVFQT",
    "index_uid": "spot-trade-etl_exlogs:01JZS10GJQXVHDP72FC2XJN54T",
    "partition_id": 0,
    "source_id": "_ingest-source",
    "node_id": "quickwit-indexer-1",
    "num_docs": 37103,
    "uncompressed_docs_size_in_bytes": 111738688,
    "time_range": {
      "start": 1755676201,
      "end": 1755676231
    },
    "create_timestamp": 1755676232,
    "maturity": {
      "type": "immature",
      "maturation_period_millis": 172800000
    },
    "tags": [
      "app_name!",
      "app_name:spot-trade-etl"
    ],
    "footer_offsets": {
      "start": 17010937,
      "end": 17023033
    },
    "delete_opstamp": 0,
    "num_merge_ops": 0,
    "doc_mapping_uid": "01JZS10GJPZMKRNWPP4YZBPRY5"
  },
  {
    "split_state": "Published",
    "update_timestamp": 1755676840,
    "publish_timestamp": 1755676840,
    "version": "0.9",
    "split_id": "01K337WZ9CF81Z48RG0FPXTY5B",
    "index_uid": "spot-trade-etl_exlogs:01JZS10GJQXVHDP72FC2XJN54T",
    "partition_id": 0,
    "source_id": "_ingest-source",
    "node_id": "quickwit-indexer-7",
    "num_docs": 377859,
    "uncompressed_docs_size_in_bytes": 1127572890,
    "time_range": {
      "start": 1755676750,
      "end": 1755676834
    },
    "create_timestamp": 1755676839,
    "maturity": {
      "type": "immature",
      "maturation_period_millis": 172800000
    },
    "tags": [
      "app_name!",
      "app_name:isolatedbalanceservice",
      "app_name:kafkaservice",
      "app_name:orderkafkacounterconsumer",
      "app_name:publishadaptor",
      "app_name:spotbalanceservice",
      "app_name:tradedetailservice"
    ],
    "footer_offsets": {
      "start": 169363916,
      "end": 169403055
    },
    "delete_opstamp": 0,
    "num_merge_ops": 1,
    "doc_mapping_uid": "01K337V0YBCQX3B0BDHGZBBBFM"
  },
  {
    "split_state": "MarkedForDeletion",
    "update_timestamp": 1755676236,
    "publish_timestamp": 1755676236,
    "version": "0.9",
    "split_id": "01K3379M7NH0WBHF2Z827B7FZY",
    "index_uid": "spot-trade-etl_exlogs:01JZS10GJQXVHDP72FC2XJN54T",
    "partition_id": 0,
    "source_id": "_ingest-source",
    "node_id": "quickwit-indexer-6",
    "num_docs": 27112,
    "uncompressed_docs_size_in_bytes": 81336549,
    "time_range": {
      "start": 1755676200,
      "end": 1755676229
    },
    "create_timestamp": 1755676231,
    "maturity": {
      "type": "immature",
      "maturation_period_millis": 172800000
    },
    "tags": [
      "app_name!",
      "app_name:spot-trade-etl"
    ],
    "footer_offsets": {
      "start": 12433661,
      "end": 12444731
    },
    "delete_opstamp": 0,
    "num_merge_ops": 0,
    "doc_mapping_uid": "01JZS10GJPZMKRNWPP4YZBPRY5"
  },
  {
    "split_state": "Published",
    "update_timestamp": 1755212085,
    "publish_timestamp": 1755212085,
    "version": "0.9",
    "split_id": "01K2NCBQTMYYTRC03WAWHYRW7W",
    "index_uid": "spot-trade-etl_exlogs:01JZS10GJQXVHDP72FC2XJN54T",
    "partition_id": 0,
    "source_id": "_ingest-source",
    "node_id": "quickwit-indexer-0",
    "num_docs": 15418795,
    "uncompressed_docs_size_in_bytes": 46302172094,
    "time_range": {
      "start": 1755208585,
      "end": 1755211654
    },
    "create_timestamp": 1755211966,
    "maturity": {
      "type": "mature"
    },
    "tags": [
      "app_name!",
      "app_name:spot-trade-etl"
    ],
    "footer_offsets": {
      "start": 6877313999,
      "end": 6878343730
    },
    "delete_opstamp": 0,
    "num_merge_ops": 3,
    "doc_mapping_uid": "01JZS10GJPZMKRNWPP4YZBPRY5"
  },
  {
    "split_state": "Published",
    "update_timestamp": 1755370273,
    "publish_timestamp": 1755370273,
    "version": "0.9",
    "split_id": "01K2T39JXKAJDVW73HFZ16M43T",
    "index_uid": "spot-trade-etl_exlogs:01JZS10GJQXVHDP72FC2XJN54T",
    "partition_id": 0,
    "source_id": "_ingest-source",
    "node_id": "quickwit-indexer-3",
    "num_docs": 11589080,
    "uncompressed_docs_size_in_bytes": 34771352380,
    "time_range": {
      "start": 1755367830,
      "end": 1755369891
    },
    "create_timestamp": 1755370173,
    "maturity": {
      "type": "mature"
    },
    "tags": [
      "app_name!",
      "app_name:spot-trade-etl"
    ],
    "footer_offsets": {
      "start": 5154319706,
      "end": 5155091247
    },
    "delete_opstamp": 0,
    "num_merge_ops": 3,
    "doc_mapping_uid": "01JZS10GJPZMKRNWPP4YZBPRY5"
  },

Expected value:

"tags": [
      "app_name!",
      "app_name:spot-trade-etl"
    ],

Get value:

"tags": [
      "app_name!",
      "app_name:isolatedbalanceservice",
      "app_name:kafkaservice",
      "app_name:orderkafkacounterconsumer",
      "app_name:publishadaptor",
      "app_name:spotbalanceservice",
      "app_name:tradedetailservice"
    ],

1. Output of quickwit --version

Quickwit 0.8.0 (x86_64-unknown-linux-gnu 2025-04-08T17:10:33Z 206ebf7)

The report provides no source file or test entry point. Start by reproducing the issue with the supplied Quickwit 0.8.0 configuration, comparing tag_fields output before and after adding uri to field_mappings; done means app_name tags remain unchanged after schema changes.