---
title: "blobexpansion create"
slug: "blobexpansion-create"
tags: ["5.5"]
updated: 2026-10-27T23:00:54Z
published: 2026-10-27T23:00:54Z
canonical: "docs.vastdata.com/blobexpansion-create"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# blobexpansion create

This command configures parsing for Kafka events. Fields in the the event message are specified for parsing, as well as a database table in which the parsed message information is saved. The table must already exist. Columns are created in the target table for the fields that are parsed, if they do not exist already.

## Usage

```plaintext
vcli: admin> blobexpansion create --database-name DATABASE 
                                  --table-name TABLE
                                  --target-table-name TABLE 
                                  --arrow-schema ARROW_SCHEMA
                                 [--tenant-id  TENANT]
                                 [--target-table-schema TARGET_SCHEMA]
                                 [--expansion-format EXPANSION_FORMAT]
                                 [--source-column-name COLUMN]
                                 [--copy-source-column]
                                 [--flatten-path]
                                 [--flatten-delimiter FLATTEN_DELIMITER]
```

## Required Parameters

| `--database-name DATABASE` | Kafka bucket name containing the source topic. |
| --- | --- |
| `--table-name TABLE` | Source Kafka topic name. |
| `--target-table-name TABLE` | Target database table name for expanded data. |
| `--arrow-schema ARROW_SCHEMA` | Column definitions as a comma-separate list of name-type pairs. These are the fields (and their type) in the Kafka event source that are parsed. They are parsed into columns of the same name and type in the target table. Columns are created in the target database table if they do not already exist. Example `--arrow-schema id-int64,status-string,score-double` This selects fields `id, status`, and `score`, for parsing from event messages. |

## Options

| `--tenant-id TENANT` | Tenant ID (optional) for the schema. |
| --- | --- |
| `--source-column-name COLUMN` | Source column name (only 'value' is supported) |
| `--target-table-schema TARGET_SCHEMA` | Target table schema (optional) |
| `--expansion-format EXPANSION_FORMAT` | The format of the source column, that is expanded (only 'json' is supported) |
| `--copy-source-column` | If set, the raw source event message (in binary JSON format) is copied to the target table. |
| `--flatten-path` | Flatten nested JSON paths. If set, nested JSON paths are parsed as a flat path. Example: this JSON block: ```plaintext "user": { "profile": { "name": "Alice", "age": 30 } } ``` is parsed to user_profile_name, user_profile_age (where the delimiter is '_'). |
| `--flatten-delimiter FLATTEN_DELIMITER` | Delimiter for flattened paths (default: '__') |

## Example

This example shows the `blobexpansion create` command with sample values.

```plaintext
vcli: admin> blobexpansion create --tenant-id 1 --database-name kafka_bucket --table-name my_topic --source-column-name value --target-table-name expanded_data --target-table-schema public --expansion-format json --arrow-schema col1-string,col2-int,col3-float --copy-source-column --flatten-path --flatten-delimiter __
```