March 2019
Intermediate to advanced
394 pages
11h 4m
English
Content preview from Mastering MongoDB 4.x - Second Edition
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Index intersection
Index intersection refers to the concept of using more than one index to fulfill a query. This was added fairly recently, and is not perfect yet; however we can exploit it to consolidate our indexes.
We can verify whether an index intersection happened in a query by using explain() on the query and witnessing an AND_SORTED or AND_HASH stage in the executed query plan.
Index intersection can happen when we use OR ($or) queries, by using a different index for each OR clause. Index intersection can happen when we use AND queries, and we have either complete indexes for each AND clause or index prefixes for some (or all) of the clauses.
For example, consider a query on our books collection, as follows:
> db.books.find({ "isbn":"101", ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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