[WIP] Check constraints

[richraid21]

Adds check constraint methods to both column and table level APIs

See Postgres Check Constraint Docs

Use case:

await knex.schema.createTable('_test', (t) => {
        t.increments()
        t.text('name').notNullable().check('name != NULL') // Stupid example, but shows chaining
        t.date('created')
        t.date('updated')
        
        t.check('updated >= created')
    })

TODO

• Determine name scheme for supporting multiple table-level constraints

• Determine API for named and default-named constraints

• Postgres Implementation https://www.postgresql.org/docs/9.4/ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS

• Mysql Implementation Unsupported See "Check Constraints" https://dev.mysql.com/doc/refman/8.0/en/create-table-check-constraints.html

• Maria Implementation

• SQL Server Implementation https://www.w3schools.com/sql/sql_check.asp

• Oracle Implementation https://docs.oracle.com/cd/E17952_01/mysql-8.0-en/create-table-check-constraints.html

• Tests for all above

• Documentation

Still need to write tests and documentation

• Closes Support CHECK #266

[elhigu]

Looks like this has some bugs which were commented to code rows.

Also this would need implementation for all the supported dialects, because if this is implemented only for 1 dialect it is the same just to use knex.schema.raw (there was a time when I was accepting single db implementations for some features, it was a bad decision).

Lastly tests and documentation is completely missing.

[elhigu]

I think this naming convention limits number of check constraints per table to be 1.

[elhigu]

needs to support raw() syntax, or otherwise identifier/value bindings cannot be handled properly across the dialects

[elhigu]

And there was some indentation error which caused CI to fail :)

[richraid21]

@elhigu
Regarding raw syntax, after some testing, it seems like pg doesn't support this.

The following all fail with assorted errors being thrown in pg:

await knex.raw('alter table _test3 add constraint ? check (length(name) >= 3)', ['name_check'])
// or
await knex.raw('alter table _test3 add constraint name_check check (length(?) >= 3)', ['name'])
// or
await knex.raw('alter table _test3 add constraint name_check check (length(?) >= ?)', ['name', 3])
// or
await knex.raw('alter table _test3 add constraint ? check (length(?) >= ?)', ['name_check', 'name', 3])

[elhigu]

Probably all of those examples already throw an error because PG does not use ? for values bindings. Also identifiers are quoted / wrapped by knex, they are not passed as bindings to drivers.

e.g.

raw('?? = ?', ['colName', 'foo'])

will pass string

"colName" = $1` bindings: ['foo']

to the driver.

But it is necessary that knex can do its wrapping to make quotes right (and make use of custom identifier wrapping if it is set in knex configuration).

[GAumala]

A MySQL implementation should also be included. I'm aware that MySQL parses CHECK statements but ignores them, however, MariaDB doesn't have this limitation as of version 10.2.1. Knex with MySQL driver works seamlessly with MariaDB, so the implementation would still be useful.

I have one question though, is it currently possible to implement the CHECK statement with a raw query without having to do the whole table declaration as a raw query? Something like:

await knex.schema.createTable('_test', (t) => {
        t.increments()
        t.date('created')
        t.date('updated')
        
        t.raw('check updated >= created')
    })

[kibertoad]

@richraid21 Are you still interested in finishing this?

[OlivierCavadenti]

Superseded by #4874