Datahike Norms - Database Migration System

The datahike.norm.norm namespace provides a database migration system for Datahike databases. Norms allow you to define schema changes and data migrations that are applied exactly once to your database.

Overview

Norms are EDN files that define database migrations. Each norm contains transaction data (tx-data) and/or transaction functions (tx-fn) that are applied to the database. The norms system tracks which migrations have been applied using a special :tx/norm attribute, ensuring each migration runs only once.

Core Functions

ensure-norms!

(ensure-norms! conn)
(ensure-norms! conn file-or-resource)

Takes a Datahike connection and optionally a java.io.File or java.net.URL to specify the location of your norms. Defaults to the resource migrations. All EDN files in the folder and its subfolders are considered migration files and will be transacted in lexicographical order by filename.

update-checksums!

(update-checksums!)
(update-checksums! norms-folder)

Computes checksums for all norm files and writes them to checksums.edn. This prevents inadvertent migrations when used with version control. Always run this after adding a new norm-file to your project.

verify-checksums

(verify-checksums file-or-resource)

Verifies that norm files haven't changed by comparing the files' checksums against stored checksums. Always run this before your migrations to ensure integrity.

Norm File Format

Norm files are EDN files containing:

• :tx-data - Vector of transaction data to apply
• :tx-fn - Symbol referencing a transaction function that takes a connection and returns a vector of transactions

The filename (without extension) becomes the norm identifier keyword.

File Organization

Files are processed in lexicographical order by name. Use numeric prefixes for ordering:

resources/migrations/
  001-initial-schema.edn
  002-add-users.edn
  003-data-migration.edn
  checksums.edn

Examples

See test files in test/datahike/norm/resources/ for working examples:

• simple-test/ - Basic schema migrations
• tx-fn-test/ - Using transaction functions
• naming-and-sorting-test/ - File ordering examples

Integration

The norms system automatically creates the :tx/norm attribute to track applied migrations. Each successfully applied norm is marked to prevent re-application.