Datasette: Enhance `/tables.json` For Default Table Listing

Datasette, the powerful open-source tool for exploring and publishing data, offers a versatile API for interacting with your datasets. One crucial endpoint, /tables.json, is designed to provide a list of tables within a database. However, the current implementation has a subtle limitation: when accessed without a search query (?q=), it returns an empty list. This can be improved to automatically list all tables, offering a more intuitive and user-friendly experience. This article delves into the rationale behind this change and discusses the implementation details, ensuring a more seamless experience for Datasette users. We'll explore how to modify the /tables.json endpoint to return a list of all tables by default, even without a specific search query. We'll also address the implementation of pagination and the inclusion of a "truncate" flag to indicate if the results are limited.

The Current State of /tables.json and Its Limitations

Currently, when you access /tables.json in Datasette without any search parameters, the response is an empty list. This behavior might not be immediately obvious to users expecting to see a list of available tables. The core issue lies in the default filtering mechanism, which, without a search query, doesn't return any results. This can be problematic, particularly for new users or those exploring a database for the first time. They might assume that the database is empty when, in fact, it contains numerous tables.

The absence of a default table listing can create a less-than-ideal user experience. Users need to know how to formulate a search query to view the tables, which adds an extra step to their exploration process. This design also increases the learning curve for users unfamiliar with Datasette's search functionalities. Therefore, modifying /tables.json to return all tables by default can dramatically improve the usability and accessibility of the tool.

Addressing this limitation will make it easier for users to view all the tables in their database without needing to provide a search query. This will enhance the overall user experience and reduce the initial barrier to exploring the data.

Implementing the Change: Returning All Tables by Default

The primary goal is to modify the /tables.json endpoint to return all tables when no search query is provided. This involves adjusting the underlying query logic to fetch all table names instead of an empty set. The implementation steps might include:

1. Modifying the endpoint's code: The core logic within the Datasette codebase that handles the /tables.json request will need to be modified. This will involve altering the query that retrieves table names from the database.
2. Removing the default filter: The current filtering mechanism needs to be adjusted. The code should be modified to avoid applying any filter when a search query (?q=) is absent.
3. Testing the changes: Rigorous testing is essential to ensure that the updated endpoint correctly lists all tables without any search parameters. This involves creating test cases to verify the expected behavior and prevent regressions.
4. Consider performance: If the number of tables is very large, returning all tables at once could impact performance. Implementing pagination will be crucial to manage large datasets effectively. For now, the implementation will return the result, then add a truncate key to indicate if the result is complete.

This approach will make it easier for users to see all the tables without needing to include a search query, which will greatly improve the user experience and make the tool easier to use from the start.

Addressing Pagination and the "truncate" Flag

As the number of tables in a database grows, returning a comprehensive list in a single response can become inefficient. To address this, pagination needs to be implemented. Pagination breaks the results into multiple pages, allowing users to navigate through the tables in manageable chunks. The implementation details for pagination might include:

1. Implementing a limit: Set a default or configurable limit on the number of tables returned per page. This can be set to 100 for now.
2. Adding a ?_page= parameter: Implement a mechanism to handle page requests. Users should be able to specify the desired page number using a URL parameter such as ?_page=2 to get the second page of results.
3. Providing metadata: The response should include metadata about the pagination, such as the total number of tables, the current page number, and the number of tables per page.

In addition to pagination, a "truncate" flag will be included in the response. This flag will indicate whether the list of tables has been truncated due to the limit imposed by pagination. The presence of this flag will alert users that the full list of tables is not being displayed and that they should use pagination to view all tables.

Implementation details for the truncation flag:

1. When to apply the truncate flag: The truncate flag should be added to the returned JSON when the number of tables exceeds the set limit.
2. Add a "truncate": true entry in JSON: If the results are truncated because of pagination limits, a `