Add support for CHECK constraints

[JanJakes]

Implements support for CHECK constraints:

CREATE TABLE t (
	id INT NOT NULL CHECK (id > 0),
	name VARCHAR(255) NOT NULL CHECK (name != ''),
	score DOUBLE NOT NULL CHECK (score > 0 AND score < 100),
	data JSON CHECK (json_valid(data)),
	start_timestamp TIMESTAMP NOT NULL,
	end_timestamp TIMESTAMP NOT NULL,
	CONSTRAINT c1 CHECK (id < 10),
	CONSTRAINT c2 CHECK (start_timestamp < end_timestamp),
	CONSTRAINT c3 CHECK (length(data) < 20)
)

This includes support for:

1. CREATE TABLE with inline CHECK (...) for column definitions.
2. CREATE TABLE with CHECK (...) and CONSTRAINT ... CHECK (...) definitions.
3. ALTER TABLE ... ADD CHECK (...) and ALTER TABLE ... ADD CONSTRAINT ... CHECK (...) statements.
4. ALTER TABLE ... DROP CONSTRAINT ... statements.
5. ALTER TABLE ... DROP CHECK ... statements.
6. CHECK constraints with the NOT ENFORCED clause.

Resolves #251.

[sejas]

I'm not able to run the create table with check constraint. Maybe I'm doing something wrong during my testing steps.

I tested the PR by applying these changes to an existing Studio site mu-plugin, and when I run a CREATE TABLE, I'm getting the following error:

Next WP_SQLite_Driver_Exception: SQLSTATE[HY000]: General error: 1 no such table: _wp_sqlite_mysql_information_schema_check_constraints in /wordpress/wp-content/mu-plugins/sqlite-database-integration/wp-includes/sqlite-ast/class-wp-sqlite-driver.php:5446
Stack trace:
#0 /wordpress/wp-content/mu-plugins/sqlite-database-integration/wp-includes/sqlite-ast/class-wp-sqlite-driver.php(847): WP_SQLite_Driver->new_driver_exception('SQLSTATE[HY000]...', 'HY000', Object(PDOException))
#1 /tmp/sqlite-command/src/Import.php(54): WP_SQLite_Driver->query('CREATE TABLE `m...')
#2 /tmp/sqlite-command/src/Import.php(38): Automattic\WP_CLI\SQLite\Import->execute_statements('studio-backup-s...')
#3 /tmp/sqlite-command/src/SQLite_Command.php(45): Automattic\WP_CLI\SQLite\Import->run('studio-backup-s...', Array)
#4 [internal function]: Automattic\WP_CLI\SQLite\SQLite_Command->import(Array, Array)
#5 /tmp/sqlite-command/vendor/wp-cli/wp-cli/php/WP_CLI/Dispatcher/CommandFactory.php(100): call_user_func(Array, Array, Array)
#6 [internal function]: WP_CLI\Dispatcher\CommandFactory::WP_CLI\Dispatcher\{closure}(Array, Array)
#7 /tmp/sqlite-command/vendor/wp-cli/wp-cli/php/WP_CLI/Dispatcher/Subcommand.php(497): call_user_func(Object(Closure), Array, Array)
#8 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(470): WP_CLI\Dispatcher\Subcommand->invoke(Array, Array, Array)
#9 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(493): WP_CLI\Runner->run_command(Array, Array)
#10 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(136): WP_CLI\Runner->run_command_and_exit()
#11 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(1349): WP_CLI\Runner->do_early_invoke('after_wp_config...')
#12 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(1293): WP_CLI\Runner->load_wordpress()
#13 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/WP_CLI/Bootstrap/LaunchRunner.php(28): WP_CLI\Runner->start()
#14 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/bootstrap.php(84): WP_CLI\Bootstrap\LaunchRunner->process(Object(WP_CLI\Bootstrap\BootstrapState))
#15 phar:///tmp/wp-cli.phar/vendor/wp-cli/wp-cli/php/wp-cli.php(35): WP_CLI\bootstrap()
#16 phar:///tmp/wp-cli.phar/php/boot-phar.php(20): include('phar:///tmp/wp-...')
#17 /tmp/wp-cli.phar(4): include('phar:///tmp/wp-...')
#18 /tmp/run-cli.php(25): require('/tmp/wp-cli.pha...')
#19 {main}
  thrown in /wordpress/wp-content/mu-plugins/sqlite-database-integration/wp-includes/sqlite-ast/class-wp-sqlite-driver.php on line 5446

    at SQLImporter.importDatabase (/Users/macbookpro/Documents/projects-m3.nosync/studio/dist/main/index.js:14464:17)
    at async SQLImporter.import (/Users/macbookpro/Documents/projects-m3.nosync/studio/dist/main/index.js:14711:7)
    at async importBackup (/Users/macbookpro/Documents/projects-m3.nosync/studio/dist/main/index.js:15970:12)
    at async importSite (/Users/macbookpro/Documents/projects-m3.nosync/studio/dist/main/index.js:16427:20)
    at async Session.<anonymous> (node:electron/js2c/browser_init:2:107024)

Note the difference between the original error vs when I used the code from this PR:

- Next WP_SQLite_Driver_Exception: SQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: _wp_sqlite_mysql_information_schema_table_constraints.CONSTRAINT_NAME in /wordpress/wp-content/mu-plugins/sqlite-database-integration/wp-includes/sqlite-ast/class-wp-sqlite-driver.php:5376
+ Next WP_SQLite_Driver_Exception: SQLSTATE[HY000]: General error: 1 no such table: _wp_sqlite_mysql_information_schema_check_constraints in /wordpress/wp-content/mu-plugins/sqlite-database-integration/wp-includes/sqlite-ast/class-wp-sqlite-driver.php:5446

[adamziel]

Smart! I wonder if we could modify the grammar and replace a check clause terminal with the column definition non-terminal 🤔 Nothing blocking here, though, this is cool

[JanJakes]

@adamziel This actually comes from the information_schema.check_constraints table that stores the full MySQL CHECK expression. So the $check_constraint['CHECK_CLAUSE'] is the CHECK_CLAUSE column. We read it from there, translate it with this "hack" to SQLite, and then apply that to SQLite.

A slight difference is—MySQL normalizes the expression a bit; we keep it as it was written.

[adamziel]

The code looks great @JanJakes! We just need to create the new table and column on any site upgrading to this plugin version. Is it time to add a simple migrations system that knows which schema version we're using and upgrades us step by step? I know WordPress has one, but I'm not sure we can use it here.

[JanJakes]

The code looks great @JanJakes! We just need to create the new table and column on any site upgrading to this plugin version.

@adamziel That will happen once we tag the release, and the DB configurator will detect that the version was bumped. The call to ensure_information_schema_tables() creates tables that are missing.

@sejas That also explains why you're running into the issue. Try to update the version in these three files, and it should work. And thanks for testing!

[sejas]

@sejas That also explains why you're running into the issue. Try to update the version in these three files, and it should work. And thanks for testing!

Cool! Now that I've upgraded the plugin version, I confirm that the table is created and works as expected. Great work!.
I executed the created table with the CHECK constraint using the queries in this PR and from this issue: #251.