Step 4: Replace the user name

Derive an identifier from the source name, remove the name, then attach the identifier to the new root object.

User-name mapping

- mapping: |
    root = this.without("user_name")

    root.user_id = "user_" + this.user_name.hash(
      "hmac_sha256",
      env("USER_SALT")
    ).encode("hex").slice(0, 12)

Truncation increases collision risk, and names are weak source identifiers. Evaluate both properties before using this pattern for joins.

Next: reduce location precision.