fix(db): clean-up old mailboxes account_id+name index

[ChristophWurst]

Fixes #11931

[ChristophWurst]

/backport to stable5.5

[kesselb]

Could you also comment so we are not even adding the migration for fresh installations?

mail/lib/Migration/Version0161Date20190902103701.php

Lines 79 to 82 in 1de7fe4

	$mailboxTable->addUniqueIndex([
	'account_id',
	'name',
	]);

[kesselb]

UNIQ_22DEBD839B6B5FBA5E237E06 is the generated name for oc_mail_mailboxes .
UNIQ_45754FF89B6B5FBA5E237E06 is the generated name for mail_mailboxes.

Therefore it's hopefully enough to check for both. We should consider adding a note in our developer documentation to avoid adding indexes without an explicit name.

<?php

$abstractMaxLenght = 63;
$oracleMaxLenght = 30;

function _generateIdentifierName($columnNames, $prefix = '', $maxSize = 30) {
	$hash = implode('', array_map(static function ($column): string {
		return dechex(crc32($column));
	}, $columnNames));

	return strtoupper(substr($prefix . '_' . $hash, 0, $maxSize));
}

$indexA = _generateIdentifierName(
	array_merge(['oc_mail_mailboxes'], ['account_id', 'name']),
	'uniq',
	$abstractMaxLenght,
);

$indexB = _generateIdentifierName(
	array_merge(['oc_mail_mailboxes'], ['account_id', 'name']),
	'uniq',
	$oracleMaxLenght,
);

$indexC = _generateIdentifierName(
	array_merge(['mail_mailboxes'], ['account_id', 'name']),
	'uniq',
	$abstractMaxLenght,
);

$indexD = _generateIdentifierName(
	array_merge(['mail_mailboxes'], ['account_id', 'name']),
	'uniq',
	$oracleMaxLenght,
);


var_dump(
	$indexA,
	$indexB,
	$indexC,
	$indexD,
);

[blizzz]

UNIQ_22DEBD839B6B5FBA5E237E06 is the generated name for oc_mail_mailboxes .
UNIQ_45754FF89B6B5FBA5E237E06 is the generated name for mail_mailboxes.

Since it seems this is calculated somehow, can we just use the configured prefix (if any) and determine the expected name?

[blizzz]

Therefore it's hopefully enough to check for both. We should consider adding a note in our developer documentation to avoid adding indexes without an explicit name.

And perhaps enforce it in new code?

[kesselb]

I find it suspicious that on some systems these indexes were created with different names. Since the difference appears to be only the prefix, I suspect there was an unintended change either on our side or in Doctrine that altered how the index names were generated, leading to this situation.