如何检查索引是否存在于 Laravel 迁移中？

How can indexes be checked if they exist in a Laravel migration?

提问by Oladipo

Trying to check if a unique index exists on a table when preparing a migration, how can it be achieved?

在准备迁移时尝试检查表上是否存在唯一索引，如何实现？

Schema::table('persons', function (Blueprint $table) {
    if ($table->hasIndex('persons_body_unique')) {
        $table->dropUnique('persons_body_unique');
    }
})

Something that looks like the above. (apparently, hasIndex() doesn't exist)

看起来像上面的东西。（显然，hasIndex() 不存在）

回答by admirko

Using "doctrine-dbal" that Laravel uses is better solution:

使用 Laravel 使用的“doctrine-dbal”是更好的解决方案：

Schema::table('persons', function (Blueprint $table) {
    $sm = Schema::getConnection()->getDoctrineSchemaManager();
    $indexesFound = $sm->listTableIndexes('persons');

    if(array_key_exists("persons_body_unique", $indexesFound))
        $table->dropUnique("persons_body_unique");
})

回答by chiliNUT

The mysql query

mysql 查询

SHOW INDEXES FROM persons

SHOW INDEXES FROM persons

will give you back all of the indexes on the table, however it includes additional info other than just the names. In my setup, the column containing the name is called Key_nameso lets get a collection of key names

将为您返回表上的所有索引，但它包括除名称之外的其他信息。在我的设置中，包含名称的列被称为Key_name所以让我们获取键名称的集合

collect(DB::select("SHOW INDEXES FROM persons"))->pluck('Key_name')

And since its a collection you can use containsso finally we have:

因为它是一个你可以使用的集合，contains所以最后我们有：

if (collect(DB::select("SHOW INDEXES FROM persons"))->pluck('Key_name')->contains('persons_body_unique')) {
        $table->dropUnique('persons_body_unique');
}

回答by dipenparmar12

In the simple form, you can do this

以简单的形式，您可以执行此操作

Schema::table('persons', function (Blueprint $table) {
    $index_exists = collect(DB::select("SHOW INDEXES FROM persons"))->pluck('Key_name')->contains('persons_body_unique');
    if ($index_exists) {
        $table->dropUnique("persons_body_unique");
    }
})