[BUG]索引扫描删除记录不能完全删除

[warr99]

Describe the bug 走索引扫描删除记录时删除不能全部删除

Environment

• OS Version: ubuntu22.04
• CPU Arch(x86/arm): x86
• Compiler: GCC 11.4.0 x86_64-linux-gnu
• Others:

Fast Reproduce Steps(Required) Steps to reproduce the behavior: miniob> create table t (id int,age int); SUCCESS miniob> create index t_id_idx on t (id); SUCCESS miniob> insert into t values (1,10); SUCCESS miniob > insert into t values (1,11); SUCCESS miniob > insert into t values (1,12); SUCCESS miniob > select from t; id|age 1|10 1|11 1|12 miniob > delete from t where id 1; SUCCESS Expected behavior 记录应该全部被删除 miniob > select from t; id|age Actual Behavior What is the result? picture is allowed 中间的记录被跳过没有被删除 miniob > select from t; id|age 1|11 Additional context

• 导致该问题的原因是在RC BplusTreeScanner::next_entry(RID& rid, bool idx_need_increase)这个函数中查找下一个entry时，会把iter_index_++，但删除一条记录会将其对应的索引向前覆盖memmove(__item_at(index), __item_at(index + 1), (size() - index - 1) * item_size())，iter_index_++就直接跳过了下一条要获取的记录了。

[hnwyllmm]

Thanks. Do you have some suggestions? Or would you like to create a pull request?

[warr99]

Thanks. Do you have some suggestions? Or would you like to create a pull request?

To minimize code structure modifications as much as possible, my current solution is to add a boolean property called idx_need_increase_ within the IndexScanPhysicalOperator class, with a default value of true. I would also provide methods set_idx_need_increase() and get_idx_need_increase(). In the DeletePhysicalOperator::next() function, if the record deletion is successful, I would attempt to cast the PhysicalOperator* child into an IndexScanPhysicalOperator*. If the casting is successful, I would then call set_idx_need_increase() to set it to false. In the next_entry() function, I would use the provided idx_need_increase parameter to decide whether to perform the iter_index_++ operation.

If you think this approach is feasible, I can submit a pull request (PR), or you can provide me with some suggestions.

[hnwyllmm]

Thanks for your suggestion. It looks not a perfect solution.

1. Your solution only suit for deletion and cannot used in insertion scenario
2. Cast the child to specific type is not a generic method.

Do you know the method that some real-database uses, such as mysql, postgresql? And it also looked like std::iterator with insert/delete.

[warr99]

Do you mean that, similar to using erase() for deleting elements in a vector, it returns a valid iterator? I'm not very familiar with how MySQL/PostgreSQL implement this feature. Could you provide me with some keywords so that I can try to implement this solution?

[hnwyllmm]

std::iterator cannot deal with erase or insert correctly. I'm sorry that I am not familiar with mysql/postgresql too and I cannot provide any useful information too. I will trace this issue and if you have any other ideas, discussion is welcome.

[0130w]

Is it possible to fix this bug? The test samples in the competition involve this issue, and it won't pass the test if it's not fixed.