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Tools to work with Amsterdam schema.

Project description


Set of libraries and tools to work with Amsterdam schema.

Install the package with: pip install amsterdam-schema-tools. This installs the library and a command-line tool called schema, with various subcommands. A listing can be obtained from schema --help.

Subcommands that talk to a PostgreSQL database expect either a DATABASE_URL environment variable or a command line option --db-url with a DSN.

Many subcommands want to know where to find schema files. Most will look in a directory of schemas denoted by the SCHEMA_URL environment variable or the --schema-url command line option. E.g.,

schema create tables --schema-url=myschemas mydataset

will try to load the schema for mydataset from myschemas/mydataset/dataset.json.

Generate amsterdam schema from existing database tables

The --prefix argument controls whether table prefixes are removed in the schema, because that is required for Django models.

As example we can generate a BAG schema. Point DATABASE_URL to bag_v11 database and then run :

schema show tablenames | sort | awk '/^bag_/{print}' | xargs schema introspect db bag --prefix bag_ | jq

The jq formats it nicely and it can be redirected to the correct directory in the schemas repository directly.

Express amsterdam schema information in relational tables

Amsterdam schema is expressed as jsonschema. However, to make it easier for people with a more relational mind- or toolset it is possible to express amsterdam schema as a set of relational tables. These tables are meta_dataset, meta_table and meta_field.

It is possible to convert a jsonschema into the relational table structure and vice-versa.

This command converts a dataset from an existing dataset in jsonschema format:

schema import schema <id of dataset>

To convert from relational tables back to jsonschema:

schema show schema <id of dataset>

Generating amsterdam schema from existing GeoJSON files

The following command can be used to inspect and import the GeoJSON files:

schema introspect geojson <dataset-id> *.geojson > schema.json
edit schema.json  # fine-tune the table names
schema import geojson schema.json <table1> file1.geojson
schema import geojson schema.json <table2> file2.geojson

Importing GOB events

The schematools library has a module that read GOB events into database tables that are defines by an Amsterdam schema. This module can be used to read GOB events from a Kafka stream. It is also possible to read GOB events from a batch file with line-separeted events using:

schema import events <path-to-dataset> <path-to-file-with-events>

Schema Tools as a pre-commit hook

Included in the project is a pre-commit hook that can validate schema files in a project such as amsterdam-schema

To configure it extend the .pre-commit-config.yaml in the project with the schema file defintions as follows:

  - repo:
    rev: v0.20.2
      - id: validate-schema
        args: ['']
        exclude: |
                schema.+|             # exclude meta schemas

args is a one element list containing the URL to the Amsterdam Meta Schema.

validate-schema will only process json files. However not all json files are Amsterdam schema files. To exclude files or directories use exclude with pattern.

pre-commit depends on properly tagged revisions of its hooks. Hence, we should not only bump version numbers on updates to this package, but also commit a tag with the version number; see below.

Doing a release

(This is for schema-tools developers.)

We use GitHub pull requests. If your PR should produce a new release of schema-tools, make sure one of the commit increments the version number in setup.cfg appropriately. Then,

  • merge the commit in GitHub, after review;
  • pull the code from GitHub and merge it into the master branch, git checkout master && git fetch origin && git merge --ff-only origin/master;
  • tag the release X.Y.Z with git tag -a vX.Y.Z -m "Bump to vX.Y.Z";
  • push the tag to GitHub with git push origin --tags;
  • release to PyPI: make upload (requires the PyPI secret).

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