[BUG] RecordPageHandler initialize failed after observer restart.

[Double0101]

Create a table and insert some rows, then stop observer.

➜  build ✗ ./bin/obclient -s miniob.sock
miniob > create table just_a_test (id int, id2 int);
SUCCESS
miniob > insert into just_a_test values (1, 1);
SUCCESS
miniob > insert into just_a_test values (2,2);
SUCCESS
miniob > exit
--- 
### then stop observer
➜  build ✗ ./bin/obclient -s miniob.sock
miniob > select * from just_a_test;
id | id2

Restart observer, then select from the table created before. It return no record.
RecordPageHandler will be nullptr and record_page_iterator_ is invalid.

RC RecordFileScanner::fetch_next_record()
{
  RC rc = RC::SUCCESS;
  if (record_page_iterator_.is_valid()) {
    // 当前页面还是有效的，尝试看一下是否有有效记录
    rc = fetch_next_record_in_page();
  .......
}

[hnwyllmm]

How did you startup the observer?

[Double0101]

./observer -s ../miniob.sock -f ../../etc/observer.ini

[hnwyllmm]

Currently, MiniOB doesn't support durability and if you stop the observer, the data maybe lost. But this issue will be fixed in the future.
You can use sync command to dump the data in the memory into disk now.