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proj3

Project 3​

框架代码​

common/iterator​

在实现join时需要

BackTrackingIterator<Integer> iter = new BackTrackingIteratorImplementation();
iter.next();     // returns 1
iter.next();     // returns 2
iter.markPrev(); // marks the previously returned value, 2
iter.next();     // returns 3
iter.hasNext();  // returns false
iter.reset();    // reset to the marked value (line 3)
iter.hasNext();  // returns true
iter.next();     // returns 2
iter.markNext(); // mark the value to be returned next, 3
iter.next();     // returns 3
iter.hasNext();  // returns false
iter.reset();    // reset to the marked value (line 11)
iter.hasNext();  // returns true
iter.next();     // returns 3

Join Operators​

query/disk​

Scan and Special Operators​

query/QueryPlan.java​

Task1:​

理解QueryOperator​
理解Simple Nested Loop Join​
  • 重要的就是实现迭代器，嵌套的两个for循环
Block Nested Loop Join​
  • 需要实现的方法：
    • fetchNextLeftBlock
    • fetchNextRightPage
    • fetchNextRecord

Task 2: Hash Joins​

Simple Hash Join​
Grace Hash Join​

问题和总结​

Block Nested Loop Join​
  • 如何保证getBlockIterator，一次获取n页，这个操作是一次io的，没看懂