sprocket

Sprocket presents a REST API and hypertext interface for database tables.

Usage

To install sprocket and its requirements, simply run:

python3 -m pip install .

If you are using a Postgres database, you must also have the psycopg2 module installed.

To run sprocket, you must include the path to your database (for SQLite) or database configuration .ini file (for Postgres):

sprocket database.db

This will start the server on localhost:5000.

Alternatively, you can provide the URL to a PostgREST OpenAPI (aka Swagger) endpoint, such as https://www.cmi-pb.org/api/v2. Each request will be sent to the endpoint and the JSON results will be displayed as the same HTML table as providing a database.

sprocket https://www.cmi-pb.org/api/v2

The first time we send a request to the API for a given table, sprocket will store some details in a cache directory .swagger. This includes all column names in the table and total results. For large datasets, the first time you load the table may take a little bit longer. The cache is removed when sprocket exits, but if you wish to keep it to speed up the results for future runs, you can do so by including the -s/--save-cache flag. This should not be used if the data in the database is changing between runs.

Usage in Python

You can also choose to run your own Flask app that uses sprocket as a Blueprint. This is useful if you'd like to provide a URL prefix, as shown in the example below. Replace PATH_TO_DATABASE with your SQLite or PostgreSQL database, or a Swagger endpoint. You must call the prepare function to set some important global variables and create the database connection.

from flask import Flask
from sprocket import BLUEPRINT, prepare

app = Flask(__name__)
app.register_blueprint(BLUEPRINT, url_prefix="/sprocket")
prepare(PATH_TO_DATABASE)

if __name__ == '__main__':
    app.run()

Testing

To run a test version of sprocket, use the SQL file at tests/resources/test.sql to generate a new database:

sqlite3 test.db < tests/resources/test.sql

Then start the sprocket server with the default table set to test1:

sprocket test.db -t test

Command Line Options

Default table

When running sprocket with no additional arguments, the base path (/) will not resolve. To set this path to a default table, include the -t/--table option:

sprocket database.db -t tablename

Limits

sprocket will show 100 results per page by default when you first view a table. This can always be changed using the HTML form or the limit query parameter, but if you wish to change the default you can do so with -l/--limit. For example, to always show 20 results when viewing a table:

sprocket database.db -l 20

CGI script

You can also run sprocket as a CGI script using the -c/--cgi flag. For example, you can create a sprocket.sh script with the following content:

#!/usr/bin/env bash

sprocket database.db -t tablename -c

Your server may need more configuration to run this, see Server Setup in the Flask documentation.

Paths

/<table>

When provided with a table name (which must exist in the database), sending a GET request to this path will return the first 100 results from that table. By default, this is an HTML page, but you can choose to get a tsv or csv table using the format parameter below.

Optional query parameters:

• format: Export the results in given format, must be html (default), tsv, or csv
• limit: Return a different number of results, must be an integer
• offset: Return results starting after given integer (e.g., offset=5 will return results starting with the 6th result)
• order: See ORDER BY Clauses
• select: A comma-separated list of columns to include in results (no spaces)

WHERE Clauses

You can also include the names of columns as optional query parameters where the value is one of the hortizontal filtering conditions. The general pattern is <table>?<column>=<operator>.<constraint>.

The following operators are currently supported:

Operator	Meaning
eq	equals
gt	greater than
gte	greater than or equal
lt	less than
lte	less than or equal
neq	not equal
like	SQL LIKE (use * in place of %)
ilike	case insensitive LIKE
is	exact equal (true, false, null)
in	one of list values

For example, to restrict the subject column to values equal to the string "foo":

/<table>?subject=eq.foo

If the constraint of the condition contains a comma or parentheses, it must be enclosed in double quotes. Strings with whitespace do not need to be enclosed, but you can if you prefer.

/<table>?subject=eq."foo (bar)"
/<table>?subject=eq."foo, bar, baz"
/<table>?subject=eq.foo bar

The in condition accepts a list as a constraint, which is a comma-separated list (NO whitespace, unless the constraint contains whitespace) of values enclosed in parentheses:

/<table>?subject=in.(foo,bar,baz)

You can negate an operator by including the not operator:

/<table>?subject=not.in.(foo,bar,baz)

ORDER BY Clauses

You can use the order query parameter to define one or more columns to sort on. By default, this is ascending. Multiple values should be comma-separated, no whitespace.

/<table>?order=subject
/<table>?order=subject,object

You can include asc or desc keywords to specify ascending or descending results:

/<table>?order=subject.desc
/<table>?order=subject.desc,object.desc

Finally, you can specify if you wish to display nullsfirst or nullslast. These should always be the last keyword.

/<table>?order=subject.desc.nullsfirst
/<table>?order=subject.nullsfirst