MongoDB aggregation Frameworkt to Map-Reduce
I'm trying to use Map-Reduce instead of aggregation Framework but I'm really struggling with it I can't find any good tutorials on how to deal with it. Let's say I have an aggregation that return average weight and height of people distinct for female and male.
db.people.aggregate
(
$group:
_id:"$sex",
avgHeight: $avg: $toDouble:"$height",
avgWeight: $avg: $toDouble:"$weight",
)
So i assume that i need to make map fucntion that emits: sex, height and weight so it looks like this:
var mapFunction1 = function()
emit(this.sex, this.height, this.weight);
;
Then a reduce function that return averege height:
var reduceFunction1 = function(keySex, valuesHeight)
return Array.avg(valuesHeight);
;
And second reduce function for weight:
var reduceFunction2 = function(keySex, valuesWeight)
return Array.avg(valuesWeight);
;
And finally I call everything out:
db.people.mapReduce(
mapFunction1,
reduceFunction1,
reduceFunction2,
out: "map_reduce_example"
)
and when I try to run it I get error
2018-11-13T17:34:03.372+0100 E QUERY [js] TypeError: c.out is undefined :
DBCollection.prototype.mapReduce@src/mongo/shell/collection.js:1135:1
@przyklad.js:12:1
failed to load: przyklad.js
mongodb mapreduce aggregation-framework
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
add a comment |
I'm trying to use Map-Reduce instead of aggregation Framework but I'm really struggling with it I can't find any good tutorials on how to deal with it. Let's say I have an aggregation that return average weight and height of people distinct for female and male.
db.people.aggregate
(
$group:
_id:"$sex",
avgHeight: $avg: $toDouble:"$height",
avgWeight: $avg: $toDouble:"$weight",
)
So i assume that i need to make map fucntion that emits: sex, height and weight so it looks like this:
var mapFunction1 = function()
emit(this.sex, this.height, this.weight);
;
Then a reduce function that return averege height:
var reduceFunction1 = function(keySex, valuesHeight)
return Array.avg(valuesHeight);
;
And second reduce function for weight:
var reduceFunction2 = function(keySex, valuesWeight)
return Array.avg(valuesWeight);
;
And finally I call everything out:
db.people.mapReduce(
mapFunction1,
reduceFunction1,
reduceFunction2,
out: "map_reduce_example"
)
and when I try to run it I get error
2018-11-13T17:34:03.372+0100 E QUERY [js] TypeError: c.out is undefined :
DBCollection.prototype.mapReduce@src/mongo/shell/collection.js:1135:1
@przyklad.js:12:1
failed to load: przyklad.js
mongodb mapreduce aggregation-framework
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
You cannot have more than one reduce function. All your work needs to be done in a single reducer. There also really is no value in doing this outside of a learning exercise. If you were paying attention to what is happening over the past few MongoDB releases, you should realize that ALL server-side JavaScript execution is slowly but surely being removed anyway. So it's not really something "new" worth learning
– Neil Lunn
Nov 14 '18 at 0:00
add a comment |
I'm trying to use Map-Reduce instead of aggregation Framework but I'm really struggling with it I can't find any good tutorials on how to deal with it. Let's say I have an aggregation that return average weight and height of people distinct for female and male.
db.people.aggregate
(
$group:
_id:"$sex",
avgHeight: $avg: $toDouble:"$height",
avgWeight: $avg: $toDouble:"$weight",
)
So i assume that i need to make map fucntion that emits: sex, height and weight so it looks like this:
var mapFunction1 = function()
emit(this.sex, this.height, this.weight);
;
Then a reduce function that return averege height:
var reduceFunction1 = function(keySex, valuesHeight)
return Array.avg(valuesHeight);
;
And second reduce function for weight:
var reduceFunction2 = function(keySex, valuesWeight)
return Array.avg(valuesWeight);
;
And finally I call everything out:
db.people.mapReduce(
mapFunction1,
reduceFunction1,
reduceFunction2,
out: "map_reduce_example"
)
and when I try to run it I get error
2018-11-13T17:34:03.372+0100 E QUERY [js] TypeError: c.out is undefined :
DBCollection.prototype.mapReduce@src/mongo/shell/collection.js:1135:1
@przyklad.js:12:1
failed to load: przyklad.js
mongodb mapreduce aggregation-framework
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
I'm trying to use Map-Reduce instead of aggregation Framework but I'm really struggling with it I can't find any good tutorials on how to deal with it. Let's say I have an aggregation that return average weight and height of people distinct for female and male.
db.people.aggregate
(
$group:
_id:"$sex",
avgHeight: $avg: $toDouble:"$height",
avgWeight: $avg: $toDouble:"$weight",
)
So i assume that i need to make map fucntion that emits: sex, height and weight so it looks like this:
var mapFunction1 = function()
emit(this.sex, this.height, this.weight);
;
Then a reduce function that return averege height:
var reduceFunction1 = function(keySex, valuesHeight)
return Array.avg(valuesHeight);
;
And second reduce function for weight:
var reduceFunction2 = function(keySex, valuesWeight)
return Array.avg(valuesWeight);
;
And finally I call everything out:
db.people.mapReduce(
mapFunction1,
reduceFunction1,
reduceFunction2,
out: "map_reduce_example"
)
and when I try to run it I get error
2018-11-13T17:34:03.372+0100 E QUERY [js] TypeError: c.out is undefined :
DBCollection.prototype.mapReduce@src/mongo/shell/collection.js:1135:1
@przyklad.js:12:1
failed to load: przyklad.js
mongodb mapreduce aggregation-framework
mongodb mapreduce aggregation-framework
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
edited Nov 13 '18 at 16:39
Bartek Wiszenko
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
asked Nov 13 '18 at 15:46
Bartek WiszenkoBartek Wiszenko
12
12
You cannot have more than one reduce function. All your work needs to be done in a single reducer. There also really is no value in doing this outside of a learning exercise. If you were paying attention to what is happening over the past few MongoDB releases, you should realize that ALL server-side JavaScript execution is slowly but surely being removed anyway. So it's not really something "new" worth learning
– Neil Lunn
Nov 14 '18 at 0:00
add a comment |
You cannot have more than one reduce function. All your work needs to be done in a single reducer. There also really is no value in doing this outside of a learning exercise. If you were paying attention to what is happening over the past few MongoDB releases, you should realize that ALL server-side JavaScript execution is slowly but surely being removed anyway. So it's not really something "new" worth learning
– Neil Lunn
Nov 14 '18 at 0:00
You cannot have more than one reduce function. All your work needs to be done in a single reducer. There also really is no value in doing this outside of a learning exercise. If you were paying attention to what is happening over the past few MongoDB releases, you should realize that ALL server-side JavaScript execution is slowly but surely being removed anyway. So it's not really something "new" worth learning
– Neil Lunn
Nov 14 '18 at 0:00
You cannot have more than one reduce function. All your work needs to be done in a single reducer. There also really is no value in doing this outside of a learning exercise. If you were paying attention to what is happening over the past few MongoDB releases, you should realize that ALL server-side JavaScript execution is slowly but surely being removed anyway. So it's not really something "new" worth learning
– Neil Lunn
Nov 14 '18 at 0:00
add a comment |
0
active
oldest
votes
Your Answer
StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53284621%2fmongodb-aggregation-frameworkt-to-map-reduce%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
0
active
oldest
votes
0
active
oldest
votes
active
oldest
votes
active
oldest
votes
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53284621%2fmongodb-aggregation-frameworkt-to-map-reduce%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
You cannot have more than one reduce function. All your work needs to be done in a single reducer. There also really is no value in doing this outside of a learning exercise. If you were paying attention to what is happening over the past few MongoDB releases, you should realize that ALL server-side JavaScript execution is slowly but surely being removed anyway. So it's not really something "new" worth learning
– Neil Lunn
Nov 14 '18 at 0:00