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| 1 | Plugin hooks | Datasette plugins use plugin hooks to customize Datasette's behavior. These hooks are powered by the pluggy plugin system. Each plugin can implement one or more hooks using the @hookimpl decorator against a function named that matches one of the hooks documented on this page. When you implement a plugin hook you can accept any or all of the parameters that are documented as being passed to that hook. For example, you can implement the render_cell plugin hook like this even though the full documented hook signature is render_cell(row, value, column, table, database, datasette) : @hookimpl def render_cell(value, column): if column == "stars": return "*" * int(value) List of plugin hooks prepare_connection(conn, database, datasette) prepare_jinja2_environment(env, datasette) Page extras extra_template_vars(template, database, table, columns, view_name, request, datasette) extra_css_urls(template, database, table, columns, view_name, request, datasette) extra_js_urls(template, database, table, columns, view_name, request, datasette) extra_body_script(template, database, table, columns, view_name, request, datasette) publish_subcommand(publish) render_cell(row, value, column, table, database, datasette, request) register_output_re… | 42 | |
| 2 | prepare_connection(conn, database, datasette) | conn - sqlite3 connection object The connection that is being opened database - string The name of the database datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) This hook is called when a new SQLite database connection is created. You can use it to register custom SQL functions , aggregates and collations. For example: from datasette import hookimpl import random @hookimpl def prepare_connection(conn): conn.create_function( "random_integer", 2, random.randint ) This registers a SQL function called random_integer which takes two arguments and can be called like this: select random_integer(1, 10); Examples: datasette-jellyfish , datasette-jq , datasette-haversine , datasette-rure | 42 | |
| 3 | prepare_jinja2_environment(env, datasette) | env - jinja2 Environment The template environment that is being prepared datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) This hook is called with the Jinja2 environment that is used to evaluate Datasette HTML templates. You can use it to do things like register custom template filters , for example: from datasette import hookimpl @hookimpl def prepare_jinja2_environment(env): env.filters["uppercase"] = lambda u: u.upper() You can now use this filter in your custom templates like so: Table name: {{ table|uppercase }} This function can return an awaitable function if it needs to run any async code. Examples: datasette-edit-templates | 42 | |
| 4 | Page extras | These plugin hooks can be used to affect the way HTML pages for different Datasette interfaces are rendered. | 42 | |
| 5 | extra_template_vars(template, database, table, columns, view_name, request, datasette) | Extra template variables that should be made available in the rendered template context. template - string The template that is being rendered, e.g. database.html database - string or None The name of the database, or None if the page does not correspond to a database (e.g. the root page) table - string or None The name of the table, or None if the page does not correct to a table columns - list of strings or None The names of the database columns that will be displayed on this page. None if the page does not contain a table. view_name - string The name of the view being displayed. ( index , database , table , and row are the most important ones.) request - Request object or None The current HTTP request. This can be None if the request object is not available. datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) This… | 42 | |
| 6 | extra_css_urls(template, database, table, columns, view_name, request, datasette) | This takes the same arguments as extra_template_vars(...) Return a list of extra CSS URLs that should be included on the page. These can take advantage of the CSS class hooks described in Custom pages and templates . This can be a list of URLs: from datasette import hookimpl @hookimpl def extra_css_urls(): return [ "https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css" ] Or a list of dictionaries defining both a URL and an SRI hash : @hookimpl def extra_css_urls(): return [ { "url": "https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css", "sri": "sha384-9gVQ4dYFwwWSjIDZnLEWnxCjeSWFphJiwGPXr1jddIhOegiu1FwO5qRGvFXOdJZ4", } ] This function can also return an awaitable function, useful if it needs to run any async code: @hookimpl def extra_css_urls(datasette): async def inner(): db = datasette.get_database() results = await db.execute( "select url from css_files" ) return [r[0] for r in results] return inner Examples: datasette-cluster-map , datasette-vega | 42 | |
| 7 | extra_js_urls(template, database, table, columns, view_name, request, datasette) | This takes the same arguments as extra_template_vars(...) This works in the same way as extra_css_urls() but for JavaScript. You can return a list of URLs, a list of dictionaries or an awaitable function that returns those things: from datasette import hookimpl @hookimpl def extra_js_urls(): return [ { "url": "https://code.jquery.com/jquery-3.3.1.slim.min.js", "sri": "sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo", } ] You can also return URLs to files from your plugin's static/ directory, if you have one: @hookimpl def extra_js_urls(): return ["/-/static-plugins/your-plugin/app.js"] Note that your-plugin here should be the hyphenated plugin name - the name that is displayed in the list on the /-/plugins debug page. If your code uses JavaScript modules you should include the "module": True key. See Custom CSS and JavaScript for more details. @hookimpl def extra_js_urls(): return [ { "url": "/-/static-plugins/your-plugin/app.js", "module": True, } ] Examples: datasette-cluster-map , datasette-vega | 42 | |
| 8 | extra_body_script(template, database, table, columns, view_name, request, datasette) | Extra JavaScript to be added to a <script> block at the end of the <body> element on the page. This takes the same arguments as extra_template_vars(...) The template , database , table and view_name options can be used to return different code depending on which template is being rendered and which database or table are being processed. The datasette instance is provided primarily so that you can consult any plugin configuration options that may have been set, using the datasette.plugin_config(plugin_name) method documented above. This function can return a string containing JavaScript, or a dictionary as described below, or a function or awaitable function that returns a string or dictionary. Use a dictionary if you want to specify that the code should be placed in a <script type="module">...</script> element: @hookimpl def extra_body_script(): return { "module": True, "script": "console.log('Your JavaScript goes here...')", } This will add the following to the end of your page: <script type="module">console.log('Your JavaScript goes here...')</script> Example: datasette-cluster-map | 42 | |
| 9 | publish_subcommand(publish) | publish - Click publish command group The Click command group for the datasette publish subcommand This hook allows you to create new providers for the datasette publish command. Datasette uses this hook internally to implement the default cloudrun and heroku subcommands, so you can read their source to see examples of this hook in action. Let's say you want to build a plugin that adds a datasette publish my_hosting_provider --api_key=xxx mydatabase.db publish command. Your implementation would start like this: from datasette import hookimpl from datasette.publish.common import ( add_common_publish_arguments_and_options, ) import click @hookimpl def publish_subcommand(publish): @publish.command() @add_common_publish_arguments_and_options @click.option( "-k", "--api_key", help="API key for talking to my hosting provider", ) def my_hosting_provider( files, metadata, extra_options, branch, template_dir, plugins_dir, static, install, plugin_secret, version_note, secret, title, license, license_url, source, source_url, about, about_url, api_key, ): ... Examples: datasette-publish-fly , datasette-publish-vercel | 42 | |
| 10 | render_cell(row, value, column, table, database, datasette, request) | Lets you customize the display of values within table cells in the HTML table view. row - sqlite.Row The SQLite row object that the value being rendered is part of value - string, integer, float, bytes or None The value that was loaded from the database column - string The name of the column being rendered table - string or None The name of the table - or None if this is a custom SQL query database - string The name of the database datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. request - Request object The current request object If your hook returns None , it will be ignored. Use this to indicate that your hook is not able to custom render this particular value. If the hook returns a string, that string will be rendered in the table cell. If you want to return HTML markup you can do so by returning a jinja2.Markup object. You can also return an awaitable function which returns a value. Datasette will loop through… | 42 | |
| 11 | register_output_renderer(datasette) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) Registers a new output renderer, to output data in a custom format. The hook function should return a dictionary, or a list of dictionaries, of the following shape: @hookimpl def register_output_renderer(datasette): return { "extension": "test", "render": render_demo, "can_render": can_render_demo, # Optional } This will register render_demo to be called when paths with the extension .test (for example /database.test , /database/table.test , or /database/table/row.test ) are requested. render_demo is a Python function. It can be a regular function or an async def render_demo() awaitable function, depending on if it needs to make any asynchronous calls. can_render_demo is a Python function (or async def function) which accepts the same arguments as render_demo but just returns True or False . It lets Datasette know if the current SQL query can be represented by the plugin - and hence influence if a link to this output format is displayed in the user interface. If you omit the "can_render" key from the dictionary every query will be treated as being supported by the plugin. When a request is received, the "render" callback function is called with zero or more of the following arguments. Datasette will inspect your callback function and pass arguments that match its function signature. datasette - Datasette class For accessing plugin configuration and executing queries. columns - list of strings The names of the columns … | 42 | |
| 12 | register_routes(datasette) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) Register additional view functions to execute for specified URL routes. Return a list of (regex, view_function) pairs, something like this: from datasette import hookimpl, Response import html async def hello_from(request): name = request.url_vars["name"] return Response.html( "Hello from {}".format(html.escape(name)) ) @hookimpl def register_routes(): return [(r"^/hello-from/(?P<name>.*)$", hello_from)] The view functions can take a number of different optional arguments. The corresponding argument will be passed to your function depending on its named parameters - a form of dependency injection. The optional view function arguments are as follows: datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. request - Request object The current HTTP request. scope - dictionary The incoming ASGI scope dictionary. send - function The ASGI send function. receive - function The ASGI receive function. The view funct… | 42 | |
| 13 | register_commands(cli) | cli - the root Datasette Click command group Use this to register additional CLI commands Register additional CLI commands that can be run using datsette yourcommand ... . This provides a mechanism by which plugins can add new CLI commands to Datasette. This example registers a new datasette verify file1.db file2.db command that checks if the provided file paths are valid SQLite databases: from datasette import hookimpl import click import sqlite3 @hookimpl def register_commands(cli): @cli.command() @click.argument( "files", type=click.Path(exists=True), nargs=-1 ) def verify(files): "Verify that files can be opened by Datasette" for file in files: conn = sqlite3.connect(str(file)) try: conn.execute("select * from sqlite_master") except sqlite3.DatabaseError: raise click.ClickException( "Invalid database: {}".format(file) ) The new command can then be executed like so: datasette verify fixtures.db Help text (from the docstring for the function plus any defined Click arguments or options) will become available using: datasette verify --help Plugins can register multiple commands by making multiple calls to the @cli.command() decorator. Consult the Click documentation for full details on how to build a CLI command, including how to define arguments and options. Note that register_commands() plugins cannot used with the --plugins-dir mechanism - they need to be installed into the same virtual environment as Datasette using pip install . Provided it has a setup.py file (see Packaging a plugin ) you can run pip install directly against the directory in which you are developing your plugin like so: pip install -e path/t… | 42 | |
| 14 | register_facet_classes() | Return a list of additional Facet subclasses to be registered. The design of this plugin hook is unstable and may change. See issue 830 . Each Facet subclass implements a new type of facet operation. The class should look like this: class SpecialFacet(Facet): # This key must be unique across all facet classes: type = "special" async def suggest(self): # Use self.sql and self.params to suggest some facets suggested_facets = [] suggested_facets.append( { "name": column, # Or other unique name # Construct the URL that will enable this facet: "toggle_url": self.ds.absolute_url( self.request, path_with_added_args( self.request, {"_facet": column} ), ), } ) return suggested_facets async def facet_results(self): # This should execute the facet operation and return results, again # using self.sql and self.params as the starting point facet_results = [] facets_timed_out = [] facet_size = self.get_facet_size() # Do some calculations here... for column in columns_selected_for_facet: try: facet_results_values = [] # More calculations... facet_results_values.append( { "value": value, "label": label, "count": count, "toggle_url": self.ds.absolute_url( self.request, toggle_path ), "selected": selected, } ) facet_results.append( { "name": column, "results": facet_results_values, "trunc… | 42 | |
| 15 | register_permissions(datasette) | If your plugin needs to register additional permissions unique to that plugin - upload-csvs for example - you can return a list of those permissions from this hook. from datasette import hookimpl, Permission @hookimpl def register_permissions(datasette): return [ Permission( name="upload-csvs", abbr=None, description="Upload CSV files", takes_database=True, takes_resource=False, default=False, ) ] The fields of the Permission class are as follows: name - string The name of the permission, e.g. upload-csvs . This should be unique across all plugins that the user might have installed, so choose carefully. abbr - string or None An abbreviation of the permission, e.g. uc . This is optional - you can set it to None if you do not want to pick an abbreviation. Since this needs to be unique across all installed plugins it's best not to specify an abbreviation at all. If an abbreviation is provided it will be used when creating restricted signed API tokens. description - string or None A human-readable description of what the permission lets you do. Should make sense as the second part of a sentence that starts "A user with this permission can ...". takes_database - boolean True if this permission can be granted on a per-database basis, False if it is only valid at the overall Datasette instance level. takes_resource - boolean … | 42 | |
| 16 | asgi_wrapper(datasette) | Return an ASGI middleware wrapper function that will be applied to the Datasette ASGI application. This is a very powerful hook. You can use it to manipulate the entire Datasette response, or even to configure new URL routes that will be handled by your own custom code. You can write your ASGI code directly against the low-level specification, or you can use the middleware utilities provided by an ASGI framework such as Starlette . This example plugin adds a x-databases HTTP header listing the currently attached databases: from datasette import hookimpl from functools import wraps @hookimpl def asgi_wrapper(datasette): def wrap_with_databases_header(app): @wraps(app) async def add_x_databases_header( scope, receive, send ): async def wrapped_send(event): if event["type"] == "http.response.start": original_headers = ( event.get("headers") or [] ) event = { "type": event["type"], "status": event["status"], "headers": original_headers + [ [ b"x-databases", ", ".join( datasette.databases.keys() ).encode("utf-8"), ] ], } await send(event) await app(scope, receive, wrapped_send) return add_x_databases_header return wrap_with_databases_header Examples: datasette-cors , datasette-pyinstrument , datasette-total-page-time | 42 | |
| 17 | startup(datasette) | This hook fires when the Datasette application server first starts up. Here is an example that validates required plugin configuration. The server will fail to start and show an error if the validation check fails: @hookimpl def startup(datasette): config = datasette.plugin_config("my-plugin") or {} assert ( "required-setting" in config ), "my-plugin requires setting required-setting" You can also return an async function, which will be awaited on startup. Use this option if you need to execute any database queries, for example this function which creates the my_table database table if it does not yet exist: @hookimpl def startup(datasette): async def inner(): db = datasette.get_database() if "my_table" not in await db.table_names(): await db.execute_write( """ create table my_table (mycol text) """ ) return inner Potential use-cases: Run some initialization code for the plugin Create database tables that a plugin needs on startup Validate the configuration for a plugin on startup, and raise an error if it is invalid If you are writing unit tests for a plugin that uses this hook and doesn't exercise Datasette by sending any simulated requests through it you will need to explicitly call await ds.invoke_startup() in your tests. An example: @pytest.mark.asyncio async def test_my_plugin(): ds = Datasette() await ds.invoke_startup() # Rest of test goes here Examples: datasette-saved-queries , datasette-init | 42 | |
| 18 | canned_queries(datasette, database, actor) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. database - string The name of the database. actor - dictionary or None The currently authenticated actor . Use this hook to return a dictionary of additional canned query definitions for the specified database. The return value should be the same shape as the JSON described in the canned query documentation. from datasette import hookimpl @hookimpl def canned_queries(datasette, database): if database == "mydb": return { "my_query": { "sql": "select * from my_table where id > :min_id" } } The hook can alternatively return an awaitable function that returns a list. Here's an example that returns queries that have been stored in the saved_queries database table, if one exists: from datasette import hookimpl @hookimpl def canned_queries(datasette, database): async def inner(): db = datasette.get_database(database) if await db.table_exists("saved_queries"): results = await db.execute( "select name, sql from saved_queries" ) return { result["name"]: {"sql": result["sql"]} for result in results } return inner The actor parameter can be used to include the currently authenticated actor in your decision. Here's an example that returns saved queries that were saved by that actor: from datasette import hookimpl @hookimpl def canned_queries… | 42 | |
| 19 | actor_from_request(datasette, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. request - Request object The current HTTP request. This is part of Datasette's authentication and permissions system . The function should attempt to authenticate an actor (either a user or an API actor of some sort) based on information in the request. If it cannot authenticate an actor, it should return None . Otherwise it should return a dictionary representing that actor. Here's an example that authenticates the actor based on an incoming API key: from datasette import hookimpl import secrets SECRET_KEY = "this-is-a-secret" @hookimpl def actor_from_request(datasette, request): authorization = ( request.headers.get("authorization") or "" ) expected = "Bearer {}".format(SECRET_KEY) if secrets.compare_digest(authorization, expected): return {"id": "bot"} If you install this in your plugins directory you can test it like this: curl -H 'Authorization: Bearer this-is-a-secret' http://localhost:8003/-/actor.json Instead of returning a dictionary, this function can return an awaitable function which itself returns either None or a dictionary. This is useful for authentication functions that need to make a database query - for example: from datasette import hookimpl @hookimpl def actor_from_request(datasette, request): async def inner(): token = request.args.get("_token") if not token: return None # Look up ?_token=xxx in sessions table result = await datasette.get_database().execute( "select count(*) from sessions where … | 42 | |
| 20 | actors_from_ids(datasette, actor_ids) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor_ids - list of strings or integers The actor IDs to look up. The hook must return a dictionary that maps the incoming actor IDs to their full dictionary representation. Some plugins that implement social features may store the ID of the actor that performed an action - added a comment, bookmarked a table or similar - and then need a way to resolve those IDs into display-friendly actor dictionaries later on. The await datasette.actors_from_ids(actor_ids) internal method can be used to look up actors from their IDs. It will dispatch to the first plugin that implements this hook. Unlike other plugin hooks, this only uses the first implementation of the hook to return a result. You can expect users to only have a single plugin installed that implements this hook. If no plugin is installed, Datasette defaults to returning actors that are just {"id": actor_id} . The hook can return a dictionary or an awaitable function that then returns a dictionary. This example implementation returns actors from a database table: from datasette import hookimpl @hookimpl def actors_from_ids(datasette, actor_ids): db = datasette.get_database("actors") async def inner(): sql = "select id, name from actors where id in ({})".format( ", ".join("?" for _ in actor_ids) ) actors = {} for row in (await db.execute(sql, actor_ids)).rows: actor = dict(row) actors[actor["id"]] = actor return actors return inner The returned dictionary fro… | 42 | |
| 21 | jinja2_environment_from_request(datasette, request, env) | datasette - Datasette class A Datasette instance. request - Request object or None The current HTTP request, if one is available. env - Environment The Jinja2 environment that will be used to render the current page. This hook can be used to return a customized Jinja environment based on the incoming request. If you want to run a single Datasette instance that serves different content for different domains, you can do so like this: from datasette import hookimpl from jinja2 import ChoiceLoader, FileSystemLoader @hookimpl def jinja2_environment_from_request(request, env): if request and request.host == "www.niche-museums.com": return env.overlay( loader=ChoiceLoader( [ FileSystemLoader( "/mnt/niche-museums/templates" ), env.loader, ] ), enable_async=True, ) return env This uses the Jinja overlay() method to create a new environment identical to the default environment except for having a different template loader, which first looks in the /mnt/niche-museums/templates directory before falling back on the default loader. | 42 | |
| 22 | filters_from_request(request, database, table, datasette) | request - Request object The current HTTP request. database - string The name of the database. table - string The name of the table. datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. This hook runs on the table page, and can influence the where clause of the SQL query used to populate that page, based on query string arguments on the incoming request. The hook should return an instance of datasette.filters.FilterArguments which has one required and three optional arguments: return FilterArguments( where_clauses=["id > :max_id"], params={"max_id": 5}, human_descriptions=["max_id is greater than 5"], extra_context={}, ) The arguments to the FilterArguments class constructor are as follows: where_clauses - list of strings, required A list of SQL fragments that will be inserted into the SQL query, joined by the and operator. These can include :named parameters which will be populated using data in params . params - dictionary, optional Additional keyword arguments to be used when the query is executed. These should match any :arguments in the where clauses. … | 42 | |
| 23 | permission_allowed(datasette, actor, action, resource) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary The current actor, as decided by actor_from_request(datasette, request) . action - string The action to be performed, e.g. "edit-table" . resource - string or None An identifier for the individual resource, e.g. the name of the table. Called to check that an actor has permission to perform an action on a resource. Can return True if the action is allowed, False if the action is not allowed or None if the plugin does not have an opinion one way or the other. Here's an example plugin which randomly selects if a permission should be allowed or denied, except for view-instance which always uses the default permission scheme instead. from datasette import hookimpl import random @hookimpl def permission_allowed(action): if action != "view-instance": # Return True or False at random return random.random() > 0.5 # Returning None falls back to default permissions This function can alternatively return an awaitable function which itself returns True , False or None . You can use this option if you need to execute additional database queries using await datasette.execute(...) . Here's an example that allows users to view the admin_log table only if their actor id is present in the admin_users table. It aso disallows arbitrary SQL queries for the staff… | 42 | |
| 24 | register_magic_parameters(datasette) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . Magic parameters can be used to add automatic parameters to canned queries . This plugin hook allows additional magic parameters to be defined by plugins. Magic parameters all take this format: _prefix_rest_of_parameter . The prefix indicates which magic parameter function should be called - the rest of the parameter is passed as an argument to that function. To register a new function, return it as a tuple of (string prefix, function) from this hook. The function you register should take two arguments: key and request , where key is the rest_of_parameter portion of the parameter and request is the current Request object . This example registers two new magic parameters: :_request_http_version returning the HTTP version of the current request, and :_uuid_new which returns a new UUID. It also registers an :_asynclookup_key parameter, demonstrating that these functions can be asynchronous: from datasette import hookimpl from uuid import uuid4 def uuid(key, request): if key == "new": return str(uuid4()) else: raise KeyError def request(key, request): if key == "http_version": return request.scope["http_version"] else: raise KeyError async def asynclookup(key, request): return await do_something_async(key) @hookimpl def register_magic_parameters(datasette): return [ ("request", request), ("uuid", uuid), ("asynclookup", asynclookup), ] | 42 | |
| 25 | forbidden(datasette, request, message) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to render templates or execute SQL queries. request - Request object The current HTTP request. message - string A message hinting at why the request was forbidden. Plugins can use this to customize how Datasette responds when a 403 Forbidden error occurs - usually because a page failed a permission check, see Permissions . If a plugin hook wishes to react to the error, it should return a Response object . This example returns a redirect to a /-/login page: from datasette import hookimpl from urllib.parse import urlencode @hookimpl def forbidden(request, message): return Response.redirect( "/-/login?=" + urlencode({"message": message}) ) The function can alternatively return an awaitable function if it needs to make any asynchronous method calls. This example renders a template: from datasette import hookimpl, Response @hookimpl def forbidden(datasette): async def inner(): return Response.html( await datasette.render_template( "render_message.html", request=request ) ) return inner | 42 | |
| 26 | handle_exception(datasette, request, exception) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to render templates or execute SQL queries. request - Request object The current HTTP request. exception - Exception The exception that was raised. This hook is called any time an unexpected exception is raised. You can use it to record the exception. If your handler returns a Response object it will be returned to the client in place of the default Datasette error page. The handler can return a response directly, or it can return return an awaitable function that returns a response. This example logs an error to Sentry and then renders a custom error page: from datasette import hookimpl, Response import sentry_sdk @hookimpl def handle_exception(datasette, exception): sentry_sdk.capture_exception(exception) async def inner(): return Response.html( await datasette.render_template( "custom_error.html", request=request ) ) return inner Example: datasette-sentry | 42 | |
| 27 | skip_csrf(datasette, scope) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. scope - dictionary The ASGI scope for the incoming HTTP request. This hook can be used to skip CSRF protection for a specific incoming request. For example, you might have a custom path at /submit-comment which is designed to accept comments from anywhere, whether or not the incoming request originated on the site and has an accompanying CSRF token. This example will disable CSRF protection for that specific URL path: from datasette import hookimpl @hookimpl def skip_csrf(scope): return scope["path"] == "/submit-comment" If any of the currently active skip_csrf() plugin hooks return True , CSRF protection will be skipped for the request. | 42 | |
| 28 | menu_links(datasette, actor, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . request - Request object or None The current HTTP request. This can be None if the request object is not available. This hook allows additional items to be included in the menu displayed by Datasette's top right menu icon. The hook should return a list of {"href": "...", "label": "..."} menu items. These will be added to the menu. It can alternatively return an async def awaitable function which returns a list of menu items. This example adds a new menu item but only if the signed in user is "root" : from datasette import hookimpl @hookimpl def menu_links(datasette, actor): if actor and actor.get("id") == "root": return [ { "href": datasette.urls.path( "/-/edit-schema" ), "label": "Edit schema", }, ] Using datasette.urls here ensures that links in the menu will take the base_url setting into account. Examples: datasette-search-all , datasette-graphql | 42 | |
| 29 | Action hooks | Action hooks can be used to add items to the action menus that appear at the top of different pages within Datasette. Unlike menu_links() , actions which are displayed on every page, actions should only be relevant to the page the user is currently viewing. Each of these hooks should return return a list of {"href": "...", "label": "..."} menu items, with optional "description": "..." keys describing each action in more detail. They can alternatively return an async def awaitable function which, when called, returns a list of those menu items. | 42 | |
| 30 | table_actions(datasette, actor, database, table, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . database - string The name of the database. table - string The name of the table. request - Request object or None The current HTTP request. This can be None if the request object is not available. This example adds a new table action if the signed in user is "root" : from datasette import hookimpl @hookimpl def table_actions(datasette, actor, database, table): if actor and actor.get("id") == "root": return [ { "href": datasette.urls.path( "/-/edit-schema/{}/{}".format( database, table ) ), "label": "Edit schema for this table", "description": "Add, remove, rename or alter columns for this table.", } ] Example: datasette-graphql | 42 | |
| 31 | view_actions(datasette, actor, database, view, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . database - string The name of the database. view - string The name of the SQL view. request - Request object or None The current HTTP request. This can be None if the request object is not available. Like table_actions(datasette, actor, database, table, request) but for SQL views. | 42 | |
| 32 | query_actions(datasette, actor, database, query_name, request, sql, params) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . database - string The name of the database. query_name - string or None The name of the canned query, or None if this is an arbitrary SQL query. request - Request object The current HTTP request. sql - string The SQL query being executed params - dictionary The parameters passed to the SQL query, if any. Populates a "Query actions" menu on the canned query and arbitrary SQL query pages. This example adds a new query action linking to a page for explaining a query: from datasette import hookimpl import urllib @hookimpl def query_actions(datasette, database, query_name, sql): # Don't explain an explain if sql.lower().startswith("explain"): return return [ { "href": datasette.u… | 42 | |
| 33 | row_actions(datasette, actor, request, database, table, row) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . request - Request object or None The current HTTP request. database - string The name of the database. table - string The name of the table. row - sqlite.Row The SQLite row object being displayed on the page. Return links for the "Row actions" menu shown at the top of the row page. This example displays the row in JSON plus some additional debug information if the user is signed in: from datasette import hookimpl @hookimpl def row_actions(datasette, database, table, actor, row): if actor: return [ { "href": datasette.urls.instance(), "label": f"Row details for {actor['id']}", "description": json.dumps( dict(row), default=repr ), }, ] Example: datasette-enrichments | 42 | |
| 34 | database_actions(datasette, actor, database, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . database - string The name of the database. request - Request object The current HTTP request. Populates an actions menu on the database page. This example adds a new database action for creating a table, if the user has the edit-schema permission: from datasette import hookimpl @hookimpl def database_actions(datasette, actor, database): async def inner(): if not await datasette.permission_allowed( actor, "edit-schema", resource=database, default=False, ): return [] return [ { "href": datasette.urls.path( "/-/edit-schema/{}/-/create".format( database ) ), "label": "Create a table", } ] return inner Example: datasette-graphql , datasette-edit-schema | 42 | |
| 35 | homepage_actions(datasette, actor, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) , or to execute SQL queries. actor - dictionary or None The currently authenticated actor . request - Request object The current HTTP request. Populates an actions menu on the top-level index homepage of the Datasette instance. This example adds a link an imagined tool for editing the homepage, only for signed in users: from datasette import hookimpl @hookimpl def homepage_actions(datasette, actor): if actor: return [ { "href": datasette.urls.path( "/-/customize-homepage" ), "label": "Customize homepage", } ] | 42 | |
| 36 | Template slots | The following set of plugin hooks can be used to return extra HTML content that will be inserted into the corresponding page, directly below the <h1> heading. Multiple plugins can contribute content here. The order in which it is displayed can be controlled using Pluggy's call time order options . Each of these plugin hooks can return either a string or an awaitable function that returns a string. | 42 | |
| 37 | top_homepage(datasette, request) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . request - Request object The current HTTP request. Returns HTML to be displayed at the top of the Datasette homepage. | 42 | |
| 38 | top_database(datasette, request, database) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . request - Request object The current HTTP request. database - string The name of the database. Returns HTML to be displayed at the top of the database page. | 42 | |
| 39 | top_table(datasette, request, database, table) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . request - Request object The current HTTP request. database - string The name of the database. table - string The name of the table. Returns HTML to be displayed at the top of the table page. | 42 | |
| 40 | top_row(datasette, request, database, table, row) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . request - Request object The current HTTP request. database - string The name of the database. table - string The name of the table. row - sqlite.Row The SQLite row object being displayed. Returns HTML to be displayed at the top of the row page. | 42 | |
| 41 | top_query(datasette, request, database, sql) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . request - Request object The current HTTP request. database - string The name of the database. sql - string The SQL query. Returns HTML to be displayed at the top of the query results page. | 42 | |
| 42 | top_canned_query(datasette, request, database, query_name) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . request - Request object The current HTTP request. database - string The name of the database. query_name - string The name of the canned query. Returns HTML to be displayed at the top of the canned query page. | 42 | |
| 43 | Event tracking | Datasette includes an internal mechanism for tracking notable events. This can be used for analytics, but can also be used by plugins that want to listen out for when key events occur (such as a table being created) and take action in response. Plugins can register to receive events using the track_event plugin hook. They can also define their own events for other plugins to receive using the register_events() plugin hook , combined with calls to the datasette.track_event() internal method . | 42 | |
| 44 | track_event(datasette, event) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . event - Event Information about the event, represented as an instance of a subclass of the Event base class. This hook will be called any time an event is tracked by code that calls the datasette.track_event(...) internal method. The event object will always have the following properties: name : a string representing the name of the event, for example logout or create-table . actor : a dictionary representing the actor that triggered the event, or None if the event was not triggered by an actor. created : a datatime.datetime object in the timezone.utc timezone representing the time the event object was created. Other properties on the event will be available depending on the type of event. You can also access those as a dictionary using event.properties() . The events fired by Datasette core are documented here . This example plugin logs details of all events to standard error: from datasette import hookimpl import json import sys @hookimpl def track_event(event): name = event.name actor = event.actor properties = event.properties() msg = json.dumps( { "name": name, "actor": actor, "properties": properties, } ) print(msg, file=sys.stderr, flush=True) T… | 42 | |
| 45 | register_events(datasette) | datasette - Datasette class You can use this to access plugin configuration options via datasette.plugin_config(your_plugin_name) . This hook should return a list of Event subclasses that represent custom events that the plugin might send to the datasette.track_event() method. This example registers event subclasses for ban-user and unban-user events: from dataclasses import dataclass from datasette import hookimpl, Event @dataclass class BanUserEvent(Event): name = "ban-user" user: dict @dataclass class UnbanUserEvent(Event): name = "unban-user" user: dict @hookimpl def register_events(): return [BanUserEvent, UnbanUserEvent] The plugin can then call datasette.track_event(...) to send a ban-user event: await datasette.track_event( BanUserEvent(user={"id": 1, "username": "cleverbot"}) ) | 42 | |
| 46 | Getting started | 42 | ||
| 47 | Play with a live demo | The best way to experience Datasette for the first time is with a demo: global-power-plants.datasettes.com provides a searchable database of power plants around the world, using data from the World Resources Institude rendered using the datasette-cluster-map plugin. fivethirtyeight.datasettes.com shows Datasette running against over 400 datasets imported from the FiveThirtyEight GitHub repository . | 42 | |
| 48 | Follow a tutorial | Datasette has several tutorials to help you get started with the tool. Try one of the following: Exploring a database with Datasette shows how to use the Datasette web interface to explore a new database. Learn SQL with Datasette introduces SQL, and shows how to use that query language to ask questions of your data. Cleaning data with sqlite-utils and Datasette guides you through using sqlite-utils to turn a CSV file into a database that you can explore using Datasette. | 42 | |
| 49 | Datasette in your browser with Datasette Lite | Datasette Lite is Datasette packaged using WebAssembly so that it runs entirely in your browser, no Python web application server required. You can pass a URL to a CSV, SQLite or raw SQL file directly to Datasette Lite to explore that data in your browser. This example link opens Datasette Lite and loads the SQL Murder Mystery example database from Northwestern University Knight Lab . | 42 | |
| 50 | Try Datasette without installing anything using Glitch | Glitch is a free online tool for building web apps directly from your web browser. You can use Glitch to try out Datasette without needing to install any software on your own computer. Here's a demo project on Glitch which you can use as the basis for your own experiments: glitch.com/~datasette-csvs Glitch allows you to "remix" any project to create your own copy and start editing it in your browser. You can remix the datasette-csvs project by clicking this button: Find a CSV file and drag it onto the Glitch file explorer panel - datasette-csvs will automatically convert it to a SQLite database (using sqlite-utils ) and allow you to start exploring it using Datasette. If your CSV file has a latitude and longitude column you can visualize it on a map by uncommenting the datasette-cluster-map line in the requirements.txt file using the Glitch file editor. Need some data? Try this Public Art Data for the city of Seattle - hit "Export" and select "CSV" to download it as a CSV file. For more on how this works, see Running Datasette on Glitch . | 42 | |
| 51 | Using Datasette on your own computer | First, follow the Installation instructions. Now you can run Datasette against a SQLite file on your computer using the following command: datasette path/to/database.db This will start a web server on port 8001 - visit http://localhost:8001/ to access the web interface. Add -o to open your browser automatically once Datasette has started: datasette path/to/database.db -o Use Chrome on OS X? You can run datasette against your browser history like so: datasette ~/Library/Application\ Support/Google/Chrome/Default/History --nolock The --nolock option ignores any file locks. This is safe as Datasette will open the file in read-only mode. Now visiting http://localhost:8001/History/downloads will show you a web interface to browse your downloads data: http://localhost:8001/History/downloads.json will return that data as JSON: { "database": "History", "columns": [ "id", "current_path", "target_path", "start_time", "received_bytes", "total_bytes", ... ], "rows": [ [ 1, "/Users/simonw/Downloads/DropboxInstaller.dmg", "/Users/simonw/Downloads/DropboxInstaller.dmg", 13097290269022132, 626688, 0, ... ] ] } http://localhost:8001/History/downloads.json?_shape=objects will return that data as JSON in a more convenient format: { ... "rows": [ { "start_time": 13097290269022132, "interrupt_reason": 0, "hash": "", "id": 1, "site_url": "", "referrer": "https://www.dropbox.com/downloading?src=index", ... } ] } | 42 | |
| 52 | Facets | Datasette facets can be used to add a faceted browse interface to any database table. With facets, tables are displayed along with a summary showing the most common values in specified columns. These values can be selected to further filter the table. Here's an example : Facets can be specified in two ways: using query string parameters, or in metadata.json configuration for the table. | 42 | |
| 53 | Facets in query strings | To turn on faceting for specific columns on a Datasette table view, add one or more _facet=COLUMN parameters to the URL. For example, if you want to turn on facets for the city_id and state columns, construct a URL that looks like this: /dbname/tablename?_facet=state&_facet=city_id This works for both the HTML interface and the .json view. When enabled, facets will cause a facet_results block to be added to the JSON output, looking something like this: { "state": { "name": "state", "results": [ { "value": "CA", "label": "CA", "count": 10, "toggle_url": "http://...?_facet=city_id&_facet=state&state=CA", "selected": false }, { "value": "MI", "label": "MI", "count": 4, "toggle_url": "http://...?_facet=city_id&_facet=state&state=MI", "selected": false }, { "value": "MC", "label": "MC", "count": 1, "toggle_url": "http://...?_facet=city_id&_facet=state&state=MC", "selected": false } ], "truncated": false } "city_id": { "name": "city_id", "results": [ { "value": 1, "label": "San Francisco", "count": 6, "toggle_url": "http://...?_facet=city_id&_facet=state&city_id=1", "selected": false }, { "value": 2, "label": "Los Angeles", "count": 4, "toggle_url": "http://...?_facet=city_id&_facet=state&city_id=2", "selected": false }, { "value": 3, "label": "Detroit", "count": 4, "toggle_url": "http://...?_facet=city_id&_facet=state&city_id=3", "selected": false }, { "value": 4, "label": "Memnonia", "count": 1, "toggle_url": "http://...?_facet=city_id&_facet=state&city_id=4", "selected": false } ], "truncated": false } } If Datasette detect… | 42 | |
| 54 | Facets in metadata | You can turn facets on by default for specific tables by adding them to a "facets" key in a Datasette Metadata file. Here's an example that turns on faceting by default for the qLegalStatus column in the Street_Tree_List table in the sf-trees database: [[[cog from metadata_doc import metadata_example metadata_example(cog, { "databases": { "sf-trees": { "tables": { "Street_Tree_List": { "facets": ["qLegalStatus"] } } } } }) ]]] [[[end]]] Facets defined in this way will always be shown in the interface and returned in the API, regardless of the _facet arguments passed to the view. You can specify array or date facets in metadata using JSON objects with a single key of array or date and a value specifying the column, like this: [[[cog metadata_example(cog, { "facets": [ {"array": "tags"}, {"date": "created"} ] }) ]]] [[[end]]] You can change the default facet size (the number of results shown for each facet) for a table using facet_size : [[[cog metadata_example(cog, { "databases": { "sf-trees": { "tables": { "Street_Tree_List": { "facets": ["qLegalStatus"], "facet_size": 10 } } } } }) ]]] [[[end]]] | 42 | |
| 55 | Suggested facets | Datasette's table UI will suggest facets for the user to apply, based on the following criteria: For the currently filtered data are there any columns which, if applied as a facet... Will return 30 or less unique options Will return more than one unique option Will return less unique options than the total number of filtered rows And the query used to evaluate this criteria can be completed in under 50ms That last point is particularly important: Datasette runs a query for every column that is displayed on a page, which could get expensive - so to avoid slow load times it sets a time limit of just 50ms for each of those queries. This means suggested facets are unlikely to appear for tables with millions of records in them. | 42 | |
| 56 | Speeding up facets with indexes | The performance of facets can be greatly improved by adding indexes on the columns you wish to facet by. Adding indexes can be performed using the sqlite3 command-line utility. Here's how to add an index on the state column in a table called Food_Trucks : sqlite3 mydatabase.db SQLite version 3.19.3 2017-06-27 16:48:08 Enter ".help" for usage hints. sqlite> CREATE INDEX Food_Trucks_state ON Food_Trucks("state"); Or using the sqlite-utils command-line utility: sqlite-utils create-index mydatabase.db Food_Trucks state | 42 | |
| 57 | Facet by JSON array | If your SQLite installation provides the json1 extension (you can check using /-/versions ) Datasette will automatically detect columns that contain JSON arrays of values and offer a faceting interface against those columns. This is useful for modelling things like tags without needing to break them out into a new table. Example here: latest.datasette.io/fixtures/facetable?_facet_array=tags | 42 | |
| 58 | Facet by date | If Datasette finds any columns that contain dates in the first 100 values, it will offer a faceting interface against the dates of those values. This works especially well against timestamp values such as 2019-03-01 12:44:00 . Example here: latest.datasette.io/fixtures/facetable?_facet_date=created | 42 | |
| 59 | Settings | 42 | ||
| 60 | Using --setting | Datasette supports a number of settings. These can be set using the --setting name value option to datasette serve . You can set multiple settings at once like this: datasette mydatabase.db \ --setting default_page_size 50 \ --setting sql_time_limit_ms 3500 \ --setting max_returned_rows 2000 Settings can also be specified in the database.yaml configuration file . | 42 | |
| 61 | Configuration directory mode | Normally you configure Datasette using command-line options. For a Datasette instance with custom templates, custom plugins, a static directory and several databases this can get quite verbose: datasette one.db two.db \ --metadata=metadata.json \ --template-dir=templates/ \ --plugins-dir=plugins \ --static css:css As an alternative to this, you can run Datasette in configuration directory mode. Create a directory with the following structure: # In a directory called my-app: my-app/one.db my-app/two.db my-app/datasette.yaml my-app/metadata.json my-app/templates/index.html my-app/plugins/my_plugin.py my-app/static/my.css Now start Datasette by providing the path to that directory: datasette my-app/ Datasette will detect the files in that directory and automatically configure itself using them. It will serve all *.db files that it finds, will load metadata.json if it exists, and will load the templates , plugins and static folders if they are present. The files that can be included in this directory are as follows. All are optional. *.db (or *.sqlite3 or *.sqlite ) - SQLite database files that will be served by Datasette datasette.yaml - Configuration for the Datasette instance metadata.json - Metadata for those databases - metadata.yaml or metadata.yml can be used as well inspect-data.json - the result of running datasette inspect *.db --inspect-file=inspect-data.json from the configuration directory - any database files listed here will be treated as immutable, so they should not be changed while Datasette is running templates/ - a directory containing Custom templates … | 42 | |
| 62 | Settings | The following options can be set using --setting name value , or by storing them in the settings.json file for use with Configuration directory mode . | 42 | |
| 63 | default_allow_sql | Should users be able to execute arbitrary SQL queries by default? Setting this to off causes permission checks for execute-sql to fail by default. datasette mydatabase.db --setting default_allow_sql off Another way to achieve this is to add "allow_sql": false to your datasette.yaml file, as described in Controlling the ability to execute arbitrary SQL . This setting offers a more convenient way to do this. | 42 | |
| 64 | default_page_size | The default number of rows returned by the table page. You can over-ride this on a per-page basis using the ?_size=80 query string parameter, provided you do not specify a value higher than the max_returned_rows setting. You can set this default using --setting like so: datasette mydatabase.db --setting default_page_size 50 | 42 | |
| 65 | sql_time_limit_ms | By default, queries have a time limit of one second. If a query takes longer than this to run Datasette will terminate the query and return an error. If this time limit is too short for you, you can customize it using the sql_time_limit_ms limit - for example, to increase it to 3.5 seconds: datasette mydatabase.db --setting sql_time_limit_ms 3500 You can optionally set a lower time limit for an individual query using the ?_timelimit=100 query string argument: /my-database/my-table?qSpecies=44&_timelimit=100 This would set the time limit to 100ms for that specific query. This feature is useful if you are working with databases of unknown size and complexity - a query that might make perfect sense for a smaller table could take too long to execute on a table with millions of rows. By setting custom time limits you can execute queries "optimistically" - e.g. give me an exact count of rows matching this query but only if it takes less than 100ms to calculate. | 42 | |
| 66 | max_returned_rows | Datasette returns a maximum of 1,000 rows of data at a time. If you execute a query that returns more than 1,000 rows, Datasette will return the first 1,000 and include a warning that the result set has been truncated. You can use OFFSET/LIMIT or other methods in your SQL to implement pagination if you need to return more than 1,000 rows. You can increase or decrease this limit like so: datasette mydatabase.db --setting max_returned_rows 2000 | 42 | |
| 67 | max_insert_rows | Maximum rows that can be inserted at a time using the bulk insert API, see Inserting rows . Defaults to 100. You can increase or decrease this limit like so: datasette mydatabase.db --setting max_insert_rows 1000 | 42 | |
| 68 | num_sql_threads | Maximum number of threads in the thread pool Datasette uses to execute SQLite queries. Defaults to 3. datasette mydatabase.db --setting num_sql_threads 10 Setting this to 0 turns off threaded SQL queries entirely - useful for environments that do not support threading such as Pyodide . | 42 | |
| 69 | allow_facet | Allow users to specify columns they would like to facet on using the ?_facet=COLNAME URL parameter to the table view. This is enabled by default. If disabled, facets will still be displayed if they have been specifically enabled in metadata.json configuration for the table. Here's how to disable this feature: datasette mydatabase.db --setting allow_facet off | 42 | |
| 70 | default_facet_size | The default number of unique rows returned by Facets is 30. You can customize it like this: datasette mydatabase.db --setting default_facet_size 50 | 42 | |
| 71 | facet_time_limit_ms | This is the time limit Datasette allows for calculating a facet, which defaults to 200ms: datasette mydatabase.db --setting facet_time_limit_ms 1000 | 42 | |
| 72 | facet_suggest_time_limit_ms | When Datasette calculates suggested facets it needs to run a SQL query for every column in your table. The default for this time limit is 50ms to account for the fact that it needs to run once for every column. If the time limit is exceeded the column will not be suggested as a facet. You can increase this time limit like so: datasette mydatabase.db --setting facet_suggest_time_limit_ms 500 | 42 | |
| 73 | suggest_facets | Should Datasette calculate suggested facets? On by default, turn this off like so: datasette mydatabase.db --setting suggest_facets off | 42 | |
| 74 | allow_download | Should users be able to download the original SQLite database using a link on the database index page? This is turned on by default. However, databases can only be downloaded if they are served in immutable mode and not in-memory. If downloading is unavailable for either of these reasons, the download link is hidden even if allow_download is on. To disable database downloads, use the following: datasette mydatabase.db --setting allow_download off | 42 | |
| 75 | allow_signed_tokens | Should users be able to create signed API tokens to access Datasette? This is turned on by default. Use the following to turn it off: datasette mydatabase.db --setting allow_signed_tokens off Turning this setting off will disable the /-/create-token page, described here . It will also cause any incoming Authorization: Bearer dstok_... API tokens to be ignored. | 42 | |
| 76 | max_signed_tokens_ttl | Maximum allowed expiry time for signed API tokens created by users. Defaults to 0 which means no limit - tokens can be created that will never expire. Set this to a value in seconds to limit the maximum expiry time. For example, to set that limit to 24 hours you would use: datasette mydatabase.db --setting max_signed_tokens_ttl 86400 This setting is enforced when incoming tokens are processed. | 42 | |
| 77 | default_cache_ttl | Default HTTP caching max-age header in seconds, used for Cache-Control: max-age=X . Can be over-ridden on a per-request basis using the ?_ttl= query string parameter. Set this to 0 to disable HTTP caching entirely. Defaults to 5 seconds. datasette mydatabase.db --setting default_cache_ttl 60 | 42 | |
| 78 | cache_size_kb | Sets the amount of memory SQLite uses for its per-connection cache , in KB. datasette mydatabase.db --setting cache_size_kb 5000 | 42 | |
| 79 | allow_csv_stream | Enables the CSV export feature where an entire table (potentially hundreds of thousands of rows) can be exported as a single CSV file. This is turned on by default - you can turn it off like this: datasette mydatabase.db --setting allow_csv_stream off | 42 | |
| 80 | max_csv_mb | The maximum size of CSV that can be exported, in megabytes. Defaults to 100MB. You can disable the limit entirely by settings this to 0: datasette mydatabase.db --setting max_csv_mb 0 | 42 | |
| 81 | truncate_cells_html | In the HTML table view, truncate any strings that are longer than this value. The full value will still be available in CSV, JSON and on the individual row HTML page. Set this to 0 to disable truncation. datasette mydatabase.db --setting truncate_cells_html 0 | 42 | |
| 82 | force_https_urls | Forces self-referential URLs in the JSON output to always use the https:// protocol. This is useful for cases where the application itself is hosted using HTTP but is served to the outside world via a proxy that enables HTTPS. datasette mydatabase.db --setting force_https_urls 1 | 42 | |
| 83 | template_debug | This setting enables template context debug mode, which is useful to help understand what variables are available to custom templates when you are writing them. Enable it like this: datasette mydatabase.db --setting template_debug 1 Now you can add ?_context=1 or &_context=1 to any Datasette page to see the context that was passed to that template. Some examples: https://latest.datasette.io/?_context=1 https://latest.datasette.io/fixtures?_context=1 https://latest.datasette.io/fixtures/roadside_attractions?_context=1 | 42 | |
| 84 | trace_debug | This setting enables appending ?_trace=1 to any page in order to see the SQL queries and other trace information that was used to generate that page. Enable it like this: datasette mydatabase.db --setting trace_debug 1 Some examples: https://latest.datasette.io/?_trace=1 https://latest.datasette.io/fixtures/roadside_attractions?_trace=1 See datasette.tracer for details on how to hook into this mechanism as a plugin author. | 42 | |
| 85 | base_url | If you are running Datasette behind a proxy, it may be useful to change the root path used for the Datasette instance. For example, if you are sending traffic from https://www.example.com/tools/datasette/ through to a proxied Datasette instance you may wish Datasette to use /tools/datasette/ as its root URL. You can do that like so: datasette mydatabase.db --setting base_url /tools/datasette/ | 42 | |
| 86 | Configuring the secret | Datasette uses a secret string to sign secure values such as cookies. If you do not provide a secret, Datasette will create one when it starts up. This secret will reset every time the Datasette server restarts though, so things like authentication cookies and API tokens will not stay valid between restarts. You can pass a secret to Datasette in two ways: with the --secret command-line option or by setting a DATASETTE_SECRET environment variable. datasette mydb.db --secret=SECRET_VALUE_HERE Or: export DATASETTE_SECRET=SECRET_VALUE_HERE datasette mydb.db One way to generate a secure random secret is to use Python like this: python3 -c 'import secrets; print(secrets.token_hex(32))' cdb19e94283a20f9d42cca50c5a4871c0aa07392db308755d60a1a5b9bb0fa52 Plugin authors make use of this signing mechanism in their plugins using .sign(value, namespace="default") and .unsign(value, namespace="default") . | 42 | |
| 87 | Using secrets with datasette publish | The datasette publish and datasette package commands both generate a secret for you automatically when Datasette is deployed. This means that every time you deploy a new version of a Datasette project, a new secret will be generated. This will cause signed cookies to become invalid on every fresh deploy. You can fix this by creating a secret that will be used for multiple deploys and passing it using the --secret option: datasette publish cloudrun mydb.db --service=my-service --secret=cdb19e94283a20f9d42cca5 | 42 | |
| 88 | Upgrade guide | 42 | ||
| 89 | Datasette 0.X -> 1.0 | This section reviews breaking changes Datasette 1.0 has when upgrading from a 0.XX version. For new features that 1.0 offers, see the Changelog . | 42 | |
| 90 | New URL for SQL queries | Prior to 1.0a14 the URL for executing a SQL query looked like this: /databasename?sql=select+1 # Or for JSON: /databasename.json?sql=select+1 This endpoint served two purposes: without a ?sql= it would list the tables in the database, but with that option it would return results of a query instead. The URL for executing a SQL query now looks like this: /databasename/-/query?sql=select+1 # Or for JSON: /databasename/-/query.json?sql=select+1 This isn't a breaking change. API calls to the older /databasename?sql=... endpoint will redirect to the new databasename/-/query?sql=... endpoint. Upgrading to the new URL is recommended to avoid the overhead of the additional redirect. | 42 | |
| 91 | Metadata changes | Metadata was completely revamped for Datasette 1.0. There are a number of related breaking changes, from the metadata.yaml file to Python APIs, that you'll need to consider when upgrading. | 42 | |
| 92 | Before Datasette 1.0, the metadata.yaml file became a kitchen sink if a mix of metadata, configuration, and settings. Now metadata.yaml is strictly for metaata (ex title and descriptions of database and tables, licensing info, etc). Other settings have been moved to a datasette.yml configuration file, described in Configuration . To start Datasette with both metadata and configuration files, run it like this: datasette --metadata metadata.yaml --config datasette.yaml # Or the shortened version: datasette -m metadata.yml -c datasette.yml | 42 | ||
| 93 | Upgrading an existing | The datasette-upgrade plugin can be used to split a Datasette 0.x.x metadata.yaml (or .json ) file into separate metadata.yaml and datasette.yaml files. First, install the plugin: datasette install datasette-upgrade Then run it like this to produce the two new files: datasette upgrade metadata-to-config metadata.json -m metadata.yml -c datasette.yml | 42 | |
| 94 | Metadata "fallback" has been removed | Certain keys in metadata like license used to "fallback" up the chain of ownership. For example, if you set an MIT to a database and a table within that database did not have a specified license, then that table would inherit an MIT license. This behavior has been removed in Datasette 1.0. Now license fields must be placed on all items, including individual databases and tables. | 42 | |
| 95 | The | In Datasette 0.x plugins could implement a get_metadata() plugin hook to customize how metadata was retrieved for different instances, databases and tables. This hook could be inefficient, since some pages might load metadata for many different items (to list a large number of tables, for example) which could result in a large number of calls to potentially expensive plugin hook implementations. As of Datasette 1.0a14 (2024-08-05), the get_metadata() hook has been deprecated: # ❌ DEPRECATED in Datasette 1.0 @hookimpl def get_metadata(datasette, key, database, table): pass Instead, plugins are encouraged to interact directly with Datasette's in-memory metadata tables in SQLite using the following methods on the Datasette class : get_instance_metadata() and set_instance_metadata() get_database_metadata() and set_database_metadata() get_resource_metadata() and set_resource_metadata() get_column_metadata() and set_column_metadata() A plugin that stores or calculates its own metadata can implement the startup(datasette) hook to populate those items on startup, and then call those methods while it is running to persist any new metadata changes. | 42 | |
| 96 | The | As of Datasette 1.0a14 , the root level /metadata.json endpoint has been removed. Metadata for tables will become available through currently in-development extras in a future alpha. | 42 | |
| 97 | The | As of Datasette 1.0a14 , the .metadata() method on the Datasette Python API has been removed. Instead, one should use the following methods on a Datasette class: get_instance_metadata() get_database_metadata() get_resource_metadata() get_column_metadata() | 42 | |
| 98 | JSON API | Datasette provides a JSON API for your SQLite databases. Anything you can do through the Datasette user interface can also be accessed as JSON via the API. To access the API for a page, either click on the .json link on that page or edit the URL and add a .json extension to it. | 42 | |
| 99 | Default representation | The default JSON representation of data from a SQLite table or custom query looks like this: { "ok": true, "rows": [ { "id": 3, "name": "Detroit" }, { "id": 2, "name": "Los Angeles" }, { "id": 4, "name": "Memnonia" }, { "id": 1, "name": "San Francisco" } ], "truncated": false } "ok" is always true if an error did not occur. The "rows" key is a list of objects, each one representing a row. The "truncated" key lets you know if the query was truncated. This can happen if a SQL query returns more than 1,000 results (or the max_returned_rows setting). For table pages, an additional key "next" may be present. This indicates that the next page in the pagination set can be retrieved using ?_next=VALUE . | 42 | |
| 100 | Different shapes | The _shape parameter can be used to access alternative formats for the rows key which may be more convenient for your application. There are three options: ?_shape=objects - "rows" is a list of JSON key/value objects - the default ?_shape=arrays - "rows" is a list of lists, where the order of values in each list matches the order of the columns ?_shape=array - a JSON array of objects - effectively just the "rows" key from the default representation ?_shape=array&_nl=on - a newline-separated list of JSON objects ?_shape=arrayfirst - a flat JSON array containing just the first value from each row ?_shape=object - a JSON object keyed using the primary keys of the rows _shape=arrays looks like this: { "ok": true, "next": null, "rows": [ [3, "Detroit"], [2, "Los Angeles"], [4, "Memnonia"], [1, "San Francisco"] ] } _shape=array looks like this: [ { "id": 3, "name": "Detroit" }, { "id": 2, "name": "Los Angeles" }, { "id": 4, "name": "Memnonia" }, { "id": 1, "name": "San Francisco" } ] _shape=array&_nl=on looks like this: {"id": 1, "value": "Myoporum laetum :: Myoporum"} {"id": 2, "value": "Metrosideros excelsa :: New Zealand Xmas Tree"} {"id": 3, "value": "Pinus radiata :: Monterey Pine"} _shape=arrayfirst looks like this: [1, 2, 3] _shape=object looks like this: { "1": { "id": 1, "value": "Myoporum laetum :: Myoporum" }, "2": { "id": 2, "value": "Metrosideros excelsa :… | 42 | |
| 101 | Pagination | The default JSON representation includes a "next_url" key which can be used to access the next page of results. If that key is null or missing then it means you have reached the final page of results. Other representations include pagination information in the link HTTP header. That header will look something like this: link: <https://latest.datasette.io/fixtures/sortable.json?_next=d%2Cv>; rel="next" Here is an example Python function built using requests that returns a list of all of the paginated items from one of these API endpoints: def paginate(url): items = [] while url: response = requests.get(url) try: url = response.links.get("next").get("url") except AttributeError: url = None items.extend(response.json()) return items | 42 |