Fix create table if not exists when indexes already exist

[sclubricants]

This fixes #6248

This removes all code for CREATE TABLE table IF NOT EXISTS. Because all platforms do not support this statement the current implementation queries the database first to determine if the table exists. If it does then it doesn't execute the create table statement. The problem occurs when the create indexes statements are executed after the create table statement and the indexes already exists. Rather then try and apply CREATE INDEX index IF NOT EXISTS and carry through the logic, this PR removes completely the IF NOT EXISTS regime and instead relies on the query table lookup. If the table exists then there is need to execute anything. This way the code is simpler and all the problems of index creation is averted.

All the magic happens in (base) Forge here:

    public function createTable(string $table, bool $ifNotExists = false, array $attributes = [])
    {
        if ($table === '') {
            throw new InvalidArgumentException('A table name is required for that operation.');
        }

        $table = $this->db->DBPrefix . $table;

        if ($this->fields === []) {
            throw new RuntimeException('Field information is required.');
        }

        // If table exists lets stop here
        if ($ifNotExists === true && $this->db->tableExists($table)) {
            $this->reset();

            return true;
        }

        $sql = $this->_createTable($table, $attributes);

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[MGatner]

A rewording suggestion. Please also add a note to the upgrade guide. That could wait until we decide on the parameter removal.

[MGatner]

@sclubricants Thanks for splitting this out! Your issue and this very specific PR makes it much easier to understand what is happening. I like this approach, I think the only drawback is a possible race condition but since forge operations should not ever be under load in production I think the benefits outweigh that slim possibility.

[kenjis]

I don't agree that changing any existing method signature in develop (4.2.x).
These change should go at least 4.3, or 5.0.

I don't see anything particularly wrong with this PR, but it changes the behavior (SQL statements will change).
So I would like to hear a little more from others.

[MGatner]

@michalsn any chance you have time for a review?

[michalsn]

The proposed changes are reasonable and will solve the initial problem.

I can't see any real downsides maybe except for some performance decrease. But since the Forge class is mainly used during testing, we should be fine.

We just need some small tweaks.

[kenjis]

Thank you!
LGTM!

[sclubricants]

@kenjis I just realized a couple more changes.

_createTable() no longer will return a bool.

    /**
     * @return string
     *
     * @deprecated $ifNotExists is no longer used, and will be removed.
     */
    protected function _createTable(string $table, bool $ifNotExists, array $attributes)
    {

And remove from createTable() logic to handle bool from _createTable().

        if (is_bool($sql)) {
            $this->reset();
            if ($sql === false) {
                if ($this->db->DBDebug) {
                    throw new DatabaseException('This feature is not available for the database you are using.');
                }

                return false;
            }

            return true;
        }

[kenjis]

@sclubricants You are correct. Good catch!