---
title: "2026-09-08 vxData diffsim Alembic migration inspection"
description: "Verified the local Alembic generation command, migration head, and DDL for new diffsim metadata fields."
image: "https://docs.virdx.dev/img/virdx-social-card.png"
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.virdx.dev/llms.txt
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# 2026-09-08 vxData diffsim Alembic migration inspection

## Work Done

- Inspected `apps/vxdata-api` Alembic configuration and Pixi database tasks without changing application source.
- Confirmed that `pixi run -e dev db-rev "add diffsim metadata fields"` loads the dev environment and generates against the running local PostgreSQL database.
- Confirmed the migration advances the sole head from `e0c004d56529` to `220e1c044d72`.
- Verified nullable columns for `diffsim_version`, `delta_small`, and `delta_big`, and confirmed `alembic check` reports no remaining model/database differences after upgrade.

## Lessons Learned: Pitfalls

- Calling `pixi run` can refresh `pixi.lock` even for inspection commands. Prefer executables from `.pixi/envs/dev/bin/` when a lockfile-neutral check is required.
- `alembic history --indicate-current` connects to PostgreSQL because `env.py` runs online; plain `alembic heads` does not need a database connection.

## Lessons Learned: Improvements

- The vxData API guide could state that `alembic.ini`'s static URL is overridden by environment-derived settings and document `db-rev` as the preferred generation command.
- A short migration checklist should require upgrading the local DB to the current sole head before autogeneration and running `db-check` afterward.

Source: https://docs.virdx.dev/knowledge/inbox/2026-09-08-diffsim-vxdata-alembic-migration-inspection/index.mdx