The document discusses various options for processing and aggregating data in MongoDB, including the Aggregation Framework, MapReduce, and connecting MongoDB to external systems like Hadoop. The Aggregation Framework is described as a flexible way to query and transform data in MongoDB using a JSON-like syntax and pipeline stages. MapReduce is presented as more versatile but also more complex to implement. Connecting to external systems like Hadoop allows processing large amounts of data across clusters.

1. Principal Solutions Architect, MongoDB, Inc.
Asya Kamsky
Data Processing and
Aggregation Options
#BigDataCamp @MongoDB @asya999

2. Applications and data
Store
Process
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3. Big Data
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4. Big Data in MongoDB
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5. Big Data in MongoDB
• An ideal operational database
• High performance for storage and
retrieval at large scale
• Robust query interface for intelligent
operations
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6. MongoDB data processing
options
Data Processing andAggregation Options in MongoDB / Asya
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7. Big Data in MongoDB
Pre-aggregate in MongoDB for real-time queries
Process in MongoDB using Aggregation
Framework
Process in MongoDB using Map/Reduce
Process outside MongoDB using Hadoop and
other external tools
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8. Aggregation Framework
Data Processing andAggregation Options in MongoDB / Asya
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9. Aggregation Framework
• Declared in JSON, executes in C++
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10. Aggregation Framework
• Declared in JSON, executes in C++
• Flexible, functional, and simple
Data Processing andAggregation Options in MongoDB / Asya
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11. Aggregation Framework
• Declared in JSON, executes in C++
• Flexible, functional, and simple
• Plays nice with sharding
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12. Pipeline
ps ax | grep mongod | head 1
Piping command line operations
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13. Pipeline
$match $group | $sort|
Piping aggregation operations
Stream of documents Result document
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14. Pipeline Operators
• $match
• $project
• $group
• $unwind
• $sort/$skip/$limit
• $redact
• $geoNear
• $out
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15. $match
• Filter documents
• Uses existing query syntax
• 2.4 added support for geospatial operations
• 2.6 added support for full text search indexes
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16. { $match : { state : "NY" } }
{
city: “SAN FRANCISCO",
loc: [-122.4614, 37.781],
state: ”CA"
}
{
city: "NEW YORK",
loc: [ -73.989, 40.731],
state: "NY"
}
{
city: “PALO ALTO",
loc: [ -122.127, 37.418],
state: ”CA"
}

17. { $match : { loc : { $geoWithin:
{$centerSphere : [ [ -122.4, 37.79 ], 20/3959 ] }
{
city: “SAN FRANCISCO",
loc: [-122.4614, 37.781],
state: ”CA"
}
{
city: "NEW YORK",
loc: [ -73.989, 40.731],
state: "NY"
}
{
city: “PALO ALTO",
loc: [ -122.127, 37.418],
state: ”CA"
}

18. $project
• Reshape documents
• Include, exclude or rename fields
• Inject computed fields
• Create sub-document fields
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19. {
loc: [-122.3892, 37.7864],
state: ”CA"
}
{
_id: "94105",
city: “SAN FRANCISCO",
loc: [-122.3892, 37.7864],
state: ”CA"
}
Selecting and Excluding
Fields
$project: { _id: 0, loc: 1, state: 1 }

20. {
zip: "94105",
cityState: ”SAN FRANCISCO,
CA"
}
{
_id: "94105",
city: “SAN FRANCISCO",
loc: [-122.3892, 37.7864],
state: ”CA"
}
$project:{zip:"$_id",cityState: {$concat:["$city", ", ", "$state" ]},_id:0}
Renaming and Computing
Fields

21. {
zip: "94105",
cityState: ”SAN FRANCISCO,
CA"
}
{
_id: "94105",
city: “SAN FRANCISCO",
loc: [-122.3892, 37.7864],
state: ”CA"
}
$project:{zip:"$_id",cityState: {$concat:["$city", ", ", "$state" ]},_id:0}
Renaming and Computing
Fields
New Field Operation

22. {
dt : {
y : 2012,
m : 9,
d : 1
},
totalprice: 123350.97,
status: "F"
}
{
_id : 6694,
cname : "Cust#000060209",
status" : "F",
totalprice : 123350.97,
orderdate : ISODate("2012-09-
01T13:11:31Z"),
lineitems: [
{ ... },
{ ... },
{ ... }
]
}
Renaming and Computing
Fields
$project : { dt: { y : { "$year" : "$orderdate" },
m : { "$month" : "$orderdate" },
d : { "$dayOfMonth" : "$orderdate" } },
totalprice : 1, status : 1, _id : 0 }

23. $group
• Group documents by an ID
– Field reference, object, constant
• Other output fields are computed
– $max, $min, $avg, $sum
– $addToSet, $push
– $first, $last
• Processes all data in memory
– can utilize external disk-based sort in 2.6
Data Processing andAggregation Options in MongoDB / Asya
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24. Find the smallest cities
within twenty miles of San
Francisco{ _id: "94306",
city: “PALO ALTO",
loc: [ -122.127, 37.418],
pop: 24309 }
{ _id: "10280",
city: "NEW YORK",
loc: [ -74.016, 40.710],
pop: 5574 }
{ _id: "94124",
city: “SAN FRANCISCO",
loc: [-122.388, 37.73],
pop: 27239 }

25. {
_id: "WOODACRE",
pop: 1524
}
{
_id: "STINSON BEACH",
pop: 630
}
{ _id: "94306",
city: “PALO ALTO",
loc: [ -122.127, 37.418],
pop: 24309 }
{ _id: "10280",
city: "NEW YORK",
loc: [ -74.016, 40.710],
pop: 5574 }
{ _id: "94124",
city: “SAN FRANCISCO",
loc: [-122.388, 37.73],
pop: 27239 }
{
_id: "BOLINAS",
pop: 1555
}
{ $match : { loc :
{ $geoWithin:
{ $centerSphere : [
[ -122.4, 37.79 ],
20/3959
]
} } }
{ $group : {
_id : "$city",
pop : {$sum:
"$pop"}
}
}
{ $sort : { "pop" : 1 } },
{ $limit : 3 }
Find the smallest cities
within twenty miles of San
Francisco

26. $unwind
• Operate on an array field
• Yield new documents for each array element
– Array replaced by element value
– Missing/empty fields → no output
– Non-array fields → error
• Pipe to $group to aggregate array values
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27. $unwind
{
title: "The Great Gatsby",
ISBN: "9781857150193",
subjects: "Long Island"
}
{ $unwind: "$subjects" }
{
title: "The Great Gatsby",
ISBN: "9781857150193",
subjects: "New York"
}
{
title: "The Great Gatsby",
ISBN: "9781857150193",
subjects: "1920s"
}
{
title: "The Great Gatsby",
ISBN: "9781857150193",
subjects: [
"Long Island",
"New York",
"1920s"
]
}

28. 2.6 Improvements
• Returns a cursor (not a document)
– just like a regular find
• New stages
– $redact
– $out
• New operators:
– set expression operators.
– $let and $map operators to allow for the use of variables.
– $literal operator and $size operator
– $cond expression object
• Integrated $text search
• Performance improvements, "explain" and more
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29. Advantages
• Runs on the server
– Uses indexes
– Uses shards
• Simple to build complex pipelines
• Easy to use from any driver
• Fast -er than other options
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30. Limitations
• Pipeline operator memory limits
– 10% of total system RAM in 2.4 and earlier
– 100MB in 2.6 but can use disk for external sort
• Some data types not allowed
– Code, CodeWithScope, etc.
• Result size limited• Result size limited (in 2.4 and earlier)
– 2.6 returns a cursor or direct output to a new collection
No result size limit!
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31. MapReduce
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32. MapReduce
• Versatile, powerful
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33. MapReduce
• Versatile, powerful
• Intended for complex data
analysis
Data Processing andAggregation Options in MongoDB / Asya
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34. MapReduce
• Versatile, powerful
• Intended for complex data
analysis
• Overkill for simple aggregations
Data Processing andAggregation Options in MongoDB / Asya
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35. MapReduce
Worker thread
calls mapper
Data Set
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36. MapReduce
Workers call Reduce()
Data Set
Output
Worker thread
calls mapper
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37. {
_id: 375,
title: "The Great Gatsby",
ISBN: "9781857150193",
available: true,
pages: 218,
chapters: 9,
subjects: [
"Long Island",
"New York",
"1920s"
],
language: "English"
}
Our Example Data

38. MapReduce
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
function map() {
var key = this.language;
emit ( key, { totalPages : this.pages, numBooks : 1
} )
}

39. MapReduce
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
function reduce(key, values) {
var result = { numBooks : 0, totalPages : 0};
values.forEach(function (value) {
result.numBooks += value.numBooks;
result.totalPages += value.totalPages;
});
return result;
}

40. MapReduce
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
function finalize( key, value ) {
if ( value.numBooks != 0 )
return value.totalPages / value.numBooks;
}

41. MapReduce
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
function finalize( key, value ) {
if ( value.numBooks != 0 )
return value.totalPages / value.numBooks;
}
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )

42. MapReduce
db.books.mapReduce(
map, reduce, {finalize: finalize, out: { inline : 1} } )
"results" : [
{
"_id" : "English",
"value" : 653
},
{
"_id" : "Russian",
"value" : 1440
}
]

43. Advantages
• Map and reduce code can be arbitrarily complex
– JavaScript, helper functions
• Results can be saved into a new collection
– replace, merge or re-reduce
• Incremental MapReduce
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44. Limitations
• Implemented with JavaScript
– Single-threaded
• Slower than Aggregation Framework
– Batch, not real time
• Harder to understand, implement, debug...
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45. Analyzing MongoDB Data in
External Systems

46. Hadoop
Framework that allows for the distributed processing
of large data sets across clusters of computers
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47. Hadoop MongoDB Connector
• MongoDB or BSON files as input/output
• Source data can be filtered with queries
• Hadoop Streaming support
– For jobs written in Python, Ruby, Node.js
• Supports Hadoop tools such as Pig and Hive
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48. Processing Big Data
• Data broken up into smaller pieces
• Process data across multiple nodes
Hadoop Hadoop Hadoop Hadoop
Hadoop Hadoop Hadoop Hadoop Hadoop
Hadoop
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49. Input splits on Non-sharded
Systems
Single Map
Reduce
Hadoop Hadoop Hadoop Hadoop Hadoop
Hadoop Hadoop Hadoop Hadoop Hadoop
Total Dataset
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50. Advantages
• Processing decoupled
from data store
• Parallel processing
• Leverage existing
infrastructure
• Java has rich set of data
processing libraries
– And other languages if
using Hadoop Streaming
• Batch processing
• Requires synchronization
between data store and
processor
• Adds complexity to
infrastructure
Disadvantages
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51. Storm
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52. Storm
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53. Storm MongoDB connector
• Spout for MongoDB oplog or capped collections
– Filtering capabilities
– Threaded and non-blocking
• Output to new or existing documents
– Insert/update bolt
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54. Aggregating MongoDB’s
Data Processing Options

55. Internal Tools
• Storing pre-aggregated data
– An exercise in schema design
• Aggregation Framework
• MapReduce
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56. External Tools
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57. Questions?

58. Principal Solutions Architect, MongoDB Inc.
Asya Kamsky
Thank You
#BigDataCamp @MongoDB @asya999