Indexing & query optimization

Indexing & Query Optimization ,[object Object]

Overview ,[object Object],[object Object],[object Object],[object Object]

Ack! My queries are slow! http://michaelprescott.typepad.com/.a/6a00d83451574c69e20134858a87a2970c-800wi

Index FTW! http://musformation.com/pics/excited.jpg

Why did that happen? Magic More Magic

Table scans 1 2 3 4 5 6 7 Looked at 7 objects Find where x equals 7

Tree Lookup 7 6 5 4 3 2 1 Looked at 3 objects Find where x equals 7

O(n) vs. O(log n) Table scan Index Number of records Number of comparisons

Using the Profiler ,[object Object],[object Object],[object Object],[object Object]

Profiler Output ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Use explain ,[object Object],[object Object],{ "cursor" : " BasicCursor ", "indexBounds" : [ ], "nscanned" : 57594, "nscannedObjects" : 57594, "n" : 3, "millis" : 108 }

Index a field ,[object Object],[object Object],[object Object]

Compound indexes ,[object Object]

Unique Indexes ,[object Object]

Embedded documents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Multikeys ,[object Object],[object Object]

Covered Indexes ,[object Object],[object Object],[object Object],db.posts.ensureIndex({“title”: 1}) db.posts.find({“title”: “My blog post:}, {title: 1, _id:0}))

Listing indexes db.posts.getIndexes()

Dropping indexes db.posts.dropIndex({“tags”: 1})

Background building db.posts.ensureIndex(..., {background: true})

Picking an Index scan Index on x Index on y Remember Terminate

Review ,[object Object],[object Object],[object Object],[object Object]

Indexing & query optimization

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Indexing & query optimization