system/Database/MySQLi/Forge.php
protected function _processIndexes(string $table): string
	{
		$sql = '';

		for ($i = 0, $c = count($this->keys); $i < $c; $i ++)
		{
			if (is_array($this->keys[$i]))
			{
				for ($i2 = 0, $c2 = count($this->keys[$i]); $i2 < $c2; $i2 ++)
				{
					if (! isset($this->fields[$this->keys[$i][$i2]]))
					{
						unset($this->keys[$i][$i2]);
						continue;
					}
				}
			}
			elseif (! isset($this->fields[$this->keys[$i]]))
			{
				unset($this->keys[$i]);
				continue;
			}

			is_array($this->keys[$i]) || $this->keys[$i] = [$this->keys[$i]];

			$unique = in_array($i, $this->uniqueKeys) ? 'UNIQUE ' : '';

			$sql .= ",\n\t{$unique}KEY " . $this->db->escapeIdentifiers(implode('_', $this->keys[$i]))
				. ' (' . implode(', ', $this->db->escapeIdentifiers($this->keys[$i])) . ')';
		}

		$this->keys = [];

		return $sql;
	}
protected function _processIndexes(string $table): string
	{
		$sql = '';

		for ($i = 0, $c = count($this->keys); $i < $c; $i ++)
		{
			if (is_array($this->keys[$i]))
			{
				for ($i2 = 0, $c2 = count($this->keys[$i]); $i2 < $c2; $i2 ++)
				{
					if (! isset($this->fields[$this->keys[$i][$i2]]))
					{
						unset($this->keys[$i][$i2]);
						continue;
					}
				}
			}
			elseif (! isset($this->fields[$this->keys[$i]]))
			{
				unset($this->keys[$i]);
				continue;
			}

			is_array($this->keys[$i]) || $this->keys[$i] = [$this->keys[$i]];

			$unique = in_array($i, $this->uniqueKeys) ? 'UNIQUE ' : '';

			$sql .= ",\n\t{$unique}KEY " . $this->db->escapeIdentifiers(implode('_', $this->keys[$i]))
				. ' (' . implode(', ', $this->db->escapeIdentifiers($this->keys[$i])) . ')';
		}

		$this->keys = [];

		return $sql;
	}
Process indexes

@param  string $table (ignored)
@return string