Think\Db\Query::getPartitionTableName PHP Method

    public function getPartitionTableName($data, $field, $rule = [])
    {
        // 对数据表进行分区
        if ($field && isset($data[$field])) {
            $value = $data[$field];
            $type = $rule['type'];
            switch ($type) {
                case 'id':
                    // 按照id范围分表
                    $step = $rule['expr'];
                    $seq = floor($value / $step) + 1;
                    break;
                case 'year':
                    // 按照年份分表
                    if (!is_numeric($value)) {
                        $value = strtotime($value);
                    }
                    $seq = date('Y', $value) - $rule['expr'] + 1;
                    break;
                case 'mod':
                    // 按照id的模数分表
                    $seq = $value % $rule['num'] + 1;
                    break;
                case 'md5':
                    // 按照md5的序列分表
                    $seq = ord(substr(md5($value), 0, 1)) % $rule['num'] + 1;
                    break;
                default:
                    if (function_exists($type)) {
                        // 支持指定函数哈希
                        $seq = ord(substr($type($value), 0, 1)) % $rule['num'] + 1;
                    } else {
                        // 按照字段的首字母的值分表
                        $seq = ord($value[0]) % $rule['num'] + 1;
                    }
            }
            return $this->getTable() . '_' . $seq;
        } else {
            // 当设置的分表字段不在查询条件或者数据中
            // 进行联合查询，必须设定 partition['num']
            $tableName = [];
            for ($i = 0; $i < $rule['num']; $i++) {
                $tableName[] = 'SELECT * FROM ' . $this->getTable() . '_' . ($i + 1);
            }
            $tableName = '( ' . implode(" UNION ", $tableName) . ') AS ' . $this->name;
            return $tableName;
        }
    }