Opening db files in immutable mode sometimes leads to the file being mutated, which causes duplication in the docker image layers: see #1836, #1480

That this happens in "immutable" mode is surprising, because the sqlite docs say that setting this should open the database as read only.

https://www.sqlite.org/c3ref/open.html

immutable: The immutable parameter is a boolean query parameter that indicates that the database file is stored on read-only media. When immutable is set, SQLite assumes that the database file cannot be changed, even by a process with higher privilege, and so the database is opened read-only and all locking and change detection is disabled. Caution: Setting the immutable property on a database file that does in fact change can result in incorrect query results and/or SQLITE_CORRUPT errors. See also: SQLITE_IOCAP_IMMUTABLE.

Perhaps this is a bug in sqlite?

:books: Documentation preview :books:: https://datasette--1870.org.readthedocs.build/en/1870/

WIP

This PR builds on #5 to continue implementing gmail import support.

Building on @UtahDave's work, these commits add a few performance and bug fixes:

• Decreased memory overhead for import by manually parsing mbox headers.
• Fixed error where some messages in the mbox would yield a row with NULL in all columns.

I will send more commits to fix any errors I encounter as I run the importer on my personal takeout data.

Refactored out the SQL for extracting aesthetic scores to use osxphotos -- adds compatbility for Big Sur via osxphotos which has been updated for new table names in Big Sur. Have not yet refactored the SQL for extracting labels which is still compatible with Big Sur.

Add support for compound foreign keys, as per issue #117

Not sure if this is the right approach. In particular I'm unsure about:

• the new ForeignKey class, which replaces the namedtuple in order to ensure that column and other_column are forced into tuples. The class does the job, but doesn't feel very elegant.
• I haven't rewritten guess_foreign_table to take account of multiple columns, so it just checks for the first column in the foreign key definition. This isn't ideal.
• I haven't added any ability to the CLI to add compound foreign keys, it's only in the python API at the moment.

The PR also contains a minor related change that columns and tables are always quoted in foreign key definitions.

:books: Documentation preview :books:: https://sqlite-utils--486.org.readthedocs.build/en/486/

Refs #1661.

Refs #1439.

• [x] Build dash_encode / dash_decode functions
• [x] Use dash encoding for row primary keys
• [x] Use dash encoding for ?_next= pagination tokens
• [x] Use dash encoding for table names in URLs
• [x] Use dash encoding for database name
• ~~Implement redirects from previous % URLs that replace those with -~~ - separate issue: #1650

Closes #398

This adds SpatiaLite helpers to the CLI.

```sh

init spatialite when creating a database

sqlite-utils create database.db --enable-wal --init-spatialite

add geometry columns

needs a database, table, geometry column name, type, with optional SRID and not-null

this will throw an error if the table doesn't already exist

sqlite-utils add-geometry-column database.db table-name geometry --srid 4326 --not-null

spatial index an existing table/column

this will throw an error it the table and column don't exist

sqlite-utils create-spatial-index database.db table-name geometry ```

Docs and tests are included.

Refs #878 - starting out with the new AsyncBase class implementing a pytest-inspired asyncio parallel execution mechanism.

Takes my test down from ten minutes to four seconds. Refs #172.

Cool project!

This fixes #136 using the suggested sql formatter library. I included the minified version in the bundle and added the relevant scripts to the codemirror includes instead of adding new files, though I could also add new files. I wanted to keep it all together, since the result of the format needs access to the editor in order to properly update the codemirror instance.