Question 6

Which of following statements is/are true?

Answer:
  • An index doesn't become multikey until a document is inserted that has an array value - True
  • Running performance tests from the mongo shell is an acceptable way to benchmark your database - False. Performance tests should be as close to production environment as possible. The mongo shell is designed for administrative tasks and ah-hoc queries, not performance benchmarks. You'd also be running in a single thread, which is unlikely how you'd be operating in production.
  • You can use the --wiredTigerDirectoryForIndexes option to place your indexes on a different disk than your data - True
  • Indexes can only be traversed forward - False - Indexes can traverse both forward as well as backward.
  • The ideal ratio between nReturned and totalKeysExamined is 1 - True.


Comments

Post a Comment

Popular posts from this blog

M201 MongoDB Performance - Labs & Final Exam Q&A

M201 MongoDB Performance Chapter-1 Introduction to MongoDB Performance Lab 1.1: Install Course Dependencies Lab 1.2: Install MongoDB Compass Chapter – 2 MongoDB Indexes Lab 2.1: Using Indexes to Sort Lab 2.2: Optimizing Compound Indexes Chapter – 3 Index Operations Lab 3.1: Explain Output Chapter 4: CURD Optimization Lab 4.1 – Equality, Sort, Range Chapter 5: Performance on Clusters Final Exam Question 1 Question 2 Question 3 Question 4 Question 5 Question 6 Question 7
Read more

Question 1

Image
Which of these statements is/are true? Answer: You can index multiple array fields in a single document with a single compound index - False   Multikey indexes allow us to index on array fields, but they do not support indexes on multiple array fields on single documents. Covered queries can sometimes still require some of your documents to be examined - False A query is covered if and only if it can be satisfied using the keys of the index. Write concern has no impact on write latency - False Different write concerns can certainly impact your write latency. Write concerns that only need acknowledgment from a primary are generally faster than ones that need acknowledgment from a majority of replica set members. Creating an ascending index on a monotonically increasing value creates index keys on the right-hand side of the index tree - True A collection scan has a logarithmic search time - False No, collection scans have a  linear  search time.
Read more

Question 7

Image
Given the following indexes: { categories: 1, price: 1 } { in_stock: 1, price: 1, name: 1 } The following documents: { price: 2.99, name: "Soap", in_stock: true, categories: ['Beauty', 'Personal Care'] } { price: 7.99, name: "Knife", in_stock: false, categories: ['Outdoors'] } And the following queries: db.products.find({ in_stock: true, price: { $gt: 1, $lt: 5 }  }).sort({  name: 1 }) db.products.find({ in_stock: true }) db.products.find({ categories: 'Beauty'  }).sort({  price: 1 }) Whic h of  following is/are true? Answer: Index #1 would provide a sort to query #3. - True Index #2 properly uses the equality, sort, range rule for query #1. - False - If we were to build an index for query #1 using the equality, sort, range rule, then the index would be: { in_stock: 1, name: 1, price: 1 }. There would be a total of 4 index keys created across all of these documents and indexes. - False - As there would be 5 to
Read more