Introduce an unsafe flag for using the new driver with SQLite < 3.37.0

[JanJakes]

Adds a WP_SQLITE_UNSAFE_ENABLE_UNSUPPORTED_VERSIONS flag for use with older versions of SQLite.

I came to the conclusion that a special flag with the word UNSAFE might be the best solution here.

By default, the new driver would still throw the following error:

The SQLite version 3.27.2 is not supported. Minimum required version is 3.37.0.

But with the new flag, it could enable accessing a database created with 3.37.0 on older SQLite versions.

An important consideration or TODO:
In this form, it would serve a basic use case, which is opening an existing database on an older SQLite for previews, including writing data to the database.

However, any new CREATE TABLE statement would fail because of the use of the STRICT keyword (General error: 1 near "STRICT": syntax error). We could address that by omitting that keyword in this mode, but maybe let's first determine whether there are use cases for it.

Resolves #252.

[sejas]

Thanks for trying to make work the STRICT tables. I tested this PR on a machine with SQLite 3.34.1 , but I'm getting a weird error when enabling the new AST driver. Database directory is not writable: /srv/htdocs/wp-content/database. There is no more information in debug.log

[akirk]

I think we should still keep a (lower than above) minimum sqlite version check here.

[adamziel]

+1

[JanJakes]

Good idea! On PHP 7.2, they seem to package 3.27.2 by default:

docker run --rm php:7.2 -r "print_r((new PDO('sqlite::memory'))->query('SELECT SQLITE_VERSION();')->fetch());"

And given that 3.27.1 and 3.27.2 were bugfix releases, I think we can go with 3.27.0 (February 2019).

[JanJakes]

@adamziel @akirk Updated with 3.27.0 as a minimum.

[sejas]

Thanks to Jan, I was able to test this PR. I confirm that enabling the correct constants made the WordPress site work on SQLite 3.34.1.

Modified constants:

• define ( 'WP_SQLITE_AST_DRIVER', true );
• define ( 'WP_SQLITE_UNSAFE_ENABLE_UNSUPPORTED_VERSIONS', true );
• And setting the correct DB_NAME : `define ( 'DB_NAME', 'database_name_here' );

I wonder if defining the WP_SQLITE_UNSAFE_ENABLE_UNSUPPORTED_VERSIONS constant is necessary, or if it should be enabled automatically when the SQLite version is older and AST is enabled.

[JanJakes]

@sejas

I wonder if defining the WP_SQLITE_UNSAFE_ENABLE_UNSUPPORTED_VERSIONS constant is necessary, or if it should be enabled automatically when the SQLite version is older and AST is enabled.

With this simple implementation, it's probably necessary (as per the An important consideration or TODO in the description of this issue). But even if we skip the STRICT keyword in all CREATE statements on older versions (= fully implement the mentioned consideration), I would be careful about this hack and would rather caution against it than activate it automatically. It can cause some incompatibilities when writing to the database, and it's technically possible to save incorrect data types, which would make the database file "corrupt" from the perspective of newer SQLite versions.