Creating the /schema endpoint

✅ What you’ll learn in this module:

• What the /schema endpoint does;
• How to define tables, primary keys, and fields;
• How to return a valid schema to Weld;
• How to test your /schema response locally.

📦 What is the /schema endpoint?

This is the first of two required endpoints.

Weld calls /schema to understand:

• What tables your connector provides
• What the primary key is for each table
• (Optionally) what fields and data types each table contains

Weld uses this schema to:

• Validate your connector
• Auto-infer missing fields
• Create the correct structure in your data warehouse

🧱 Example schema response

Here’s a minimal valid schema definition for a single table called forms:

1{
2  "schema": {
3    "forms": {
4      "primary_key": "id",
5      "fields": [
6        {
7          "name": "id",
8          "type": "string"
9        },
10        {
11          "name": "title",
12          "type": "string"
13        },
14        {
15          "name": "created_at",
16          "type": "datetime"
17        }
18      ]
19    }
20  }
21}

Weld supports the following types:

• string
• int
• long
• double
• boolean
• datetime
• array (stored as a JSON string)
• object (stored as a JSON string)
• Nullable types like ["null", "string"]

🛠 Add it to your code

Update your main.py to respond differently depending on the request path:

1import functions_framework
2from flask import jsonify, Request
3
4
5@functions_framework.http
6def handler(request: Request):
7    if request.path == "/schema":
8        return jsonify(get_schema()), 200
9    return "Hello, Weld!", 200
10
11
12def get_schema():
13    return {
14        "schema": {
15            "forms": {
16                "primary_key": "id",
17                "fields": [
18                    {"name": "id", "type": "string"},
19                    {"name": "title", "type": "string"},
20                    {"name": "created_at", "type": "datetime"}
21                ]
22            }
23        }
24    }
25

🧪 Test it locally

1. Restart your dev server:

  functions-framework --target=handler --debug

2. In Postman: - Send a GET request to http://localhost:8080/schema - You should receive the JSON schema in the response

✅ You now have a working /schema endpoint!