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![Multikeys
{“tags”:
[“mongodb”,
“indexing”],
...}
db.posts.ensureIndex({“tags”:
1})](https://image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-15-2048.jpg)
![When is an Index Used?
Index
on
{a:
1}
db.collection.find({a:
0})
db.collection.find({a:
{$in:
[0,
2]}})
db.collection.find({a:
{$gt:
5}})
db.collection.count({a:
0})
db.collection.find().sort({a:
-‐1})
Partially:
db.collection.find({b:
0}).sort({a:
-‐1})](https://image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-19-2048.jpg)
![Explain
db.collection.find(query).explain();
{
"cursor"
:
"BasicCursor",
"indexBounds"
:
[
],
"nscanned"
:
57594,
"nscannedObjects"
:
57594,
"n"
:
3
,
"millis"
:
108
}](https://image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-25-2048.jpg)
![Explain
{
"cursor"
:
"BtreeCursor
x_1",
"indexBounds"
:
[
],
"nscanned"
:
123,
"nscannedObjects"
:
123,
"n"
:
10
,
"millis"
:
4
}](https://image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-26-2048.jpg)
![Multikeys
{“tags”:
[“mongodb”,
“indexing”],
...}
db.posts.ensureIndex({“tags”:
1})](https://crownmelresort.com/image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-15-2048.jpg)
![When is an Index Used?
Index
on
{a:
1}
db.collection.find({a:
0})
db.collection.find({a:
{$in:
[0,
2]}})
db.collection.find({a:
{$gt:
5}})
db.collection.count({a:
0})
db.collection.find().sort({a:
-‐1})
Partially:
db.collection.find({b:
0}).sort({a:
-‐1})](https://crownmelresort.com/image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-19-2048.jpg)
![Explain
db.collection.find(query).explain();
{
"cursor"
:
"BasicCursor",
"indexBounds"
:
[
],
"nscanned"
:
57594,
"nscannedObjects"
:
57594,
"n"
:
3
,
"millis"
:
108
}](https://crownmelresort.com/image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-25-2048.jpg)
![Explain
{
"cursor"
:
"BtreeCursor
x_1",
"indexBounds"
:
[
],
"nscanned"
:
123,
"nscannedObjects"
:
123,
"n"
:
10
,
"millis"
:
4
}](https://crownmelresort.com/image.slidesharecdn.com/indexing-100921142822-phpapp02/75/Indexing-26-2048.jpg)
Uploaded byMike Dirolf
Indexing
Indexing in MongoDB works similarly to indexing in relational databases. An index is a data structure that can make certain queries more efficient by maintaining a sorted order of documents. Indexes are created using the ensureIndex() method and take up additional space and slow down writes. The explain() method is used to determine whether a query is using an index.
More Related Content
Indexing
- 1. Indexing Mike Dirolf -‐ @mdirolf -‐ 10gen, Inc. http://www.mongodb.org
- 2. What’s Easy About MongoDBIndexing? It’s almost the same as in your RDBMS
- 3. What’s Hard About MongoDBIndexing? It’s almost the same as in your RDBMS
- 4. What is anIndex? Magic scaling sauce?
- 5. What is anIndex? A data structure that can be used to make certain queries more efficient.
- 6. Indexes Maintain Order Index on {a: 1} {a: 0, b: 9} {a: 2, b: 0} {a: 3, b: 2} {a: 3, b: 7} {a: 3, b: 5} {a: 7, b: 1} {a: 9, b: 1}
- 7. Indexes Maintain Order Index on {a: 1, b: -‐1} {a: 0, b: 9} {a: 2, b: 0} {a: 3, b: 7} {a: 3, b: 5} {a: 3, b: 2} {a: 7, b: 1} {a: 9, b: 1}
- 8. B-tree Structure Index on {a: 1} [-∞, 5) [5, 10) [10, ∞) [-∞, 5) buckets [5, 7) [7, 9) [9, 10) [10, ∞) buckets {...} {...} {...} {...} {...} {...} {...} {...} {...} {...} {...}
- 9. Query for {a:7} Index [-∞, 5) [5, 10) [10, ∞) [-∞, 5) buckets [5, 7) [7, 9) [9, 10) [10, ∞) buckets {...} {...} {...} {...} {...} {...} {...} {...} {...} {...} {...} Scan
- 10. Creating Indexes An index on _id is automatic. For more, ensureIndex: db.posts.ensureIndex({“name”: 1})
- 11. Compound Indexes db.posts.ensureIndex({name: 1, date: -‐1})
- 12. Unique Indexes db.posts.ensureIndex({title: 1}, {unique: true})
- 13.
- 14. Indexing Embedded Documents db.posts.ensureIndex({“comments.author”: 1})
- 15. Multikeys {“tags”: [“mongodb”, “indexing”], ...} db.posts.ensureIndex({“tags”: 1})
- 16.
- 17.
- 18.
- 19. When is anIndex Used? Index on {a: 1} db.collection.find({a: 0}) db.collection.find({a: {$in: [0, 2]}}) db.collection.find({a: {$gt: 5}}) db.collection.count({a: 0}) db.collection.find().sort({a: -‐1}) Partially: db.collection.find({b: 0}).sort({a: -‐1})
- 20. When isn’t anIndex Used? Index on {a: 1, b: -‐1} db.collection.find({b: 0}) As a rule: try imagining how the sorted representation could help the server with your query.
- 21. Picking an Index find({x: 10, y: “foo”}) scan terminate index on x index on y remember
- 22. When are Indexes Needed? Frequently used queries Low response time
- 23. Indexes Take Up Space db.collection.totalIndexSize()
- 24. Indexes Slow Down Writes
- 25. Explain db.collection.find(query).explain(); { "cursor" : "BasicCursor", "indexBounds" : [ ], "nscanned" : 57594, "nscannedObjects" : 57594, "n" : 3 , "millis" : 108 }
- 26. Explain { "cursor" : "BtreeCursor x_1", "indexBounds" : [ ], "nscanned" : 123, "nscannedObjects" : 123, "n" : 10 , "millis" : 4 }
- 27.