Is it possible to index CSV file name without extension + literal string + CSV field value in Azure AI search?

I have CSV files on Azure Blob Storage which contain a field Type (among other fields). I use indexer parsing mode delimitedText to split them into documents - one per row. The AI enrichment tree for such a document should contain the node /document/Type.

According to https://learn.microsoft.com/en-us/azure/search/search-howto-indexing-azure-blob-storage when indexing Azure Blobs one also gets metadata nodes like /document/metadata_storage_name and /document/metadata_storage_path.

For example, suppose I have a file xyz.csv and there is a record inside with Type = abc. Then this record presumably (I think) will have /document/Type = "abc" and /document/metadata_storage_name = "xyz.csv" in the AI enrichment tree.

Assuming I get it so far, can I somehow generate a new field for the index that would combine the file name without the extension and the type using a certain literal string to separate the two?

In my example I would like this field to have the value of abc @ xyz.

Can it be done without a custom skill?

To achieve without custom skill set you need to use MergeSkill, SplitSkill and a mapping function extractTokenAtPosition to get only the file name without extension.

First, create 2 new fields filename and combinedText, both are of string type.

Next, in indexer definition you add the mapping function in field mappings like below. This extracts only filename.

"fieldMappings": [
    {
      "sourceFieldName": "AzureSearch_DocumentKey",
      "targetFieldName": "AzureSearch_DocumentKey",
      "mappingFunction": {
        "name": "base64Encode",
        "parameters": null
      }
    },
    {
      "sourceFieldName": "metadata_storage_name",
      "targetFieldName": "filename",
      "mappingFunction": {
        "name": "extractTokenAtPosition",
        "parameters": {
          "delimiter": ".",
          "position": 0
        }
      }
    }
  ],

Refer about this here.

Use text split skill to convert this string to array of string. Since it is the type accepted by merge skill.

Create a skill set like below.

{
  "name": "skillset1725958890028",
  "description": "",
  "skills": [
    {
      "@odata.type": "#Microsoft.Skills.Text.SplitSkill",
      "textSplitMode": "pages",
      "defaultLanguageCode": "en",
      "inputs": [
        {
          "name": "text",
          "source": "/document/filename"
        }
      ],
      "outputs": [
        {
          "name": "textItems",
          "targetName": "arrayresult"
        }
      ]
    },
    {
      "@odata.type": "#Microsoft.Skills.Text.MergeSkill",
      "name": "CombineFieldsSkill",
      "description": "Combines multiple fields into a single string",
      "context": "/document",
      "insertPreTag": "@",
      "insertPostTag": "",
      "inputs": [
        {
          "name": "text",
          "source": "/document/Type"
        },
        {
          "name": "itemsToInsert",
          "source": "/document/arrayresult"
        }
      ],
      "outputs": [
        {
          "name": "mergedText",
          "targetName": "combined_field"
        }
      ]
    }
  ],
  "cognitiveServices": {
    "@odata.type": "#Microsoft.Azure.Search.DefaultCognitiveServices"
  }
}

Add output field mappings in indexer to populate the results. Below is the full indexer definition.

{
  "@odata.context": "https://xyx.search.windows.net/$metadata#indexers/$entity",
  "@odata.etag": "\"0x8DCD17A4933D27D\"",
  "name": "azureblob-indexer",
  "description": "",
  "dataSourceName": "ds",
  "skillsetName": "skillset1725958890028",
  "targetIndexName": "azureblob-index",
  "disabled": null,
  "schedule": null,
  "parameters": {
    "batchSize": null,
    "maxFailedItems": 0,
    "maxFailedItemsPerBatch": 0,
    "base64EncodeKeys": null,
    "configuration": {
      "dataToExtract": "contentAndMetadata",
      "parsingMode": "delimitedText",
      "firstLineContainsHeaders": true,
      "delimitedTextDelimiter": ",",
      "delimitedTextHeaders": ""
    }
  },
  "fieldMappings": [
    {
      "sourceFieldName": "AzureSearch_DocumentKey",
      "targetFieldName": "AzureSearch_DocumentKey",
      "mappingFunction": {
        "name": "base64Encode",
        "parameters": null
      }
    },
    {
      "sourceFieldName": "metadata_storage_name",
      "targetFieldName": "filename",
      "mappingFunction": {
        "name": "extractTokenAtPosition",
        "parameters": {
          "delimiter": ".",
          "position@odata.type": "#Int64",
          "position": 0
        }
      }
    }
  ],
  "outputFieldMappings": [
    {
      "sourceFieldName": "/document/combined_field",
      "targetFieldName": "combinedText"
    }
  ],
  "cache": null,
  "encryptionKey": null
}

Output: