mongodb-lectures/9.PERFORMANCE.md

Mongo - Performance

Lesson Objectives

1. Explain indexes
2. Explain text indexes
3. Explain replication
4. Explain sharding

Explain indexes

1. db.employees.ensureIndex({name: 1});
2. db.employees.dropIndex({name: 1});
3. db.employees.ensureIndex({name: 1}, {unique: true});
4. indexes on embedded fields
5. indexes on arrays
6. db.employees.ensureIndex({name: 1, salary: -1});

Explain text indexes

1. db.articles.createIndex({ subject : "text", content : "text" })
2. drop text index
   • db.articles.getIndexes()
   • db.articles.dropIndex('index_name')
3. db.articles.find( { $text: { $search: "coffee" } } )
4. db.articles.find( { $text: { $search: "leche", $language: "es" } } )
   • stop words (a, the, and, etc)
5. db.articles.find( { $text: { $search: "bake coffee cake" } } )
6. db.articles.find( { $text: { $search: "\"coffee cake\"" } } )
7. db.articles.find( { $text: { $search: "bake coffee -cake" } } )
8. db.articles.find( { $text: { $search: "cake" } }, { score: { $meta: "textScore" } } )

db.articles.find(
   { $text: { $search: "cake" } },
   { score: { $meta: "textScore" } }
).sort( { score: { $meta: "textScore" } } )

Explain replication

1. Writes sent to secondary DBs asynchonously
2. Reads can happen on secondaries
   • although data may be stale
3. If primary goes down, a secondary is chosen to be new primary

Explain sharding

1. split data across multiple servers