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This chapter provides an in-depth look at the merge process in query processing, illustrating concepts such as input runs, output buffers, and the crucial role of duplicate elimination. Through detailed animations, key examples of input runs are presented to show how data is processed. The chapter also explains how keys are handled, including cases of duplicate keys that are ignored during merging. This engaging content is essential for those looking to grasp the fundamentals of efficient query processing and the mechanics behind merging data.
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Query Processing: The Basics Chapter 10 (animations)
Merge: An Example Input runs Output run 2 3 5 6 2 5 3 6 10 6 3 1 5 2 7 15 1 2 3 5 6 7 10 15 1 7 10 15 10 1 15 7 Input buffers Output buffer
Duplicate elimination During Merge Input runs Last key used Output run 2 3 5 6 5 2 3 6 15 6 5 1 2 3 6 3 1 2 5 15 1 2 3 5 6 15 1 3 5 15 1 5 15 3 Key 3 ignored: duplicate Key 5 ignored: duplicate Input buffers Output buffer
Block-Nested Loop Illustrated Input buffer forr r rs s … and so on Input buffer fors Output buffer
Join During Merge Illustrated r D A 1 3 p p 0 9 q q 8 7 3 s s s 5 7 u u 1 1 v v 1 3 1 3 p p p p p p p p 4 0 0 4 8 7 3 s s s s s s 7 7 7 5 7 5 7 5 7 u u u u u u u u u u u u 2 2 5 5 0 0 B E p p 4 0 r 9 s 7 t t 2 5 u u u 2 5 0 x 0 rA=Bs s
