# Inspect synthetic join expansion

**Use case:** 

Inspect many-to-many expansion and key-quality fields for two synthetic JSON arrays. This is a paid computation, not a free demo: completed reports cost $0.05, including empty/no-match results. It does not execute the join. Run for full dataset JSON; input and results are retained by the platform. Post-run data access may cost extra.

## Input

```json
{
  "leftRecords": [
    {
      "id": 1
    },
    {
      "id": 1
    },
    {
      "id": "1"
    },
    {
      "id": 2
    },
    {
      "id": null
    },
    {}
  ],
  "rightRecords": [
    {
      "key": 1
    },
    {
      "key": 1
    },
    {
      "key": 1
    },
    {
      "key": "1"
    },
    {
      "key": 3
    },
    {
      "key": true
    }
  ],
  "leftKey": "id",
  "rightKey": "key",
  "includeKeyExamples": false
}
```

## Output

```json
{
  "schemaVersion": {
    "label": "Schema version",
    "format": "string"
  },
  "leftRowCount": {
    "label": "Left rows",
    "format": "integer"
  },
  "rightRowCount": {
    "label": "Right rows",
    "format": "integer"
  },
  "cardinality": {
    "label": "Cardinality",
    "format": "string"
  },
  "innerJoinRows": {
    "label": "Inner join rows",
    "format": "integer"
  },
  "leftJoinRows": {
    "label": "Left join rows",
    "format": "integer"
  },
  "duplicates": {
    "label": "Duplicates",
    "format": "object"
  },
  "orphans": {
    "label": "Orphans",
    "format": "object"
  },
  "warnings": {
    "label": "Warnings",
    "format": "array"
  },
  "inputSha256": {
    "label": "Input SHA-256",
    "format": "string"
  }
}
```

## How it works

### 1. Sign up on Apify or log in

The Dataset Join Preflight Actor is ready to run with the inputs already set for "Inspect synthetic join expansion". [Sign up or log in](https://console.apify.com/create-task-from-example/fLgvT5D8ye7cTCpzN) and you'll land in Apify Console with a copy of this exact task.

### 2. Start the "Inspect synthetic join expansion" task

The Dataset Join Preflight Actor will start running based on the input automatically. You can also change all the input fields, like left records, right records, and more, to match your specific use case.

### 3. Receive the "Inspect synthetic join expansion" output

Monitor the progress in real time. You will be notified as soon as your dataset is complete and ready for review. Each result includes data such as schema version, left rows, right rows, and more.

### 4. Integrate into your workflow

The final output is delivered in JSON, CSV, or Excel format, ready to be plugged into your workflow. You can also [run the "Inspect synthetic join expansion" task via API](https://apify.com/l3digital/dataset-join-preflight.md).

## About this Actor

This example demonstrates how to use [Dataset Join Preflight](https://apify.com/l3digital/dataset-join-preflight.md) with a specific input configuration. Visit the [Actor detail page](https://apify.com/l3digital/dataset-join-preflight.md) to learn more, explore other use cases, and run it yourself.


## How to integrate an Actor?

This Task's input is already configured above. Use it as-is rather than inventing a new one.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For full API examples (JavaScript, Python, CLI, MCP, OpenAPI), see this Task's Actor page: https://apify.com/l3digital/dataset-join-preflight.md

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).