"myview": {
"map": "function(doc) {if(doc.type == 'call') {emit([doc.from_user, doc.to_user], doc.type);} }",
"reduce": "function (key, values) {return values;}"
}
POST request with group = true
{
"keys":[["123456"], ["123456"]]
}
How can I get unique doc based on value exists in either in from_user or to_user?
Emit the values of doc.from_user and doc.to_user as single keys.
e.g.
emit(doc.from_user, doc.type);
emit(doc.to_user, doc.type);
Every row of the view result includes the doc._id and you can also get the doc in the view result by using the query param include_docs=true.
Finally you request your view with the query param ?key="your_value" and you will get every row with that value as key.
If you want to know whether the value is from doc.from_user or doc.to_user just emit that information as part of the value or build as multi key like
emit([doc.from_user, 'from_user'], doc.type);
emit([doc.to_user, 'to_user'], doc.type);
Then you can request
?startkey=["your_value","from_user"]&endkey=["your_value","to_user"]
Related
I have this document in couchdb, I wish to write a view which can emit key combination of original "_id" and the id within "Body" with the value as the body itself.
basically if "doc" is the json:
key [ _id, "key in Body" ]
value [ doc['_id']['Body'][key in Body]
json Document
CouchDB has a detailed guide to views.
A views map function can emit multiple key-value pairs per document, so in your case you would emit each doc.Body entry.
function(doc) {
if (doc.Body) {
// get an array of own property names in doc.Body
var bodies = Object.keys(doc.Body);
// loop over all the Body entries
bodies.forEach(function (body) {
// emit key-value for each entry
emit([doc._id, body], bodies[body].body);
});
}
}
To get all bodies from doc._id = "123":
http://my.couch.host/my-db/_design/docname/_view/viewname?startkey=["123"]&endkey=["123",{}]
To get the body of doc.Body.abc from doc._id = "123":
http://my.couch.host/my-db/_design/docname/_view/viewname?startkey=["123","abc"]&endkey=["123","abc"]
See views collation and complex keys for more information.
I need to store user's info in DynamoDB and send a mail to the same user if it doesn't already exist in DynamoDB table. I am doing this in for loop. The list contains only 2 records. The issue is only the second record gets inserted in table and the mail is sent twice to the same user. Here is the code:
module.exports.AddUser = function(req, res, usersList, departmentId) {
var _emailId = "";
var _userName = "";
var _departmentId = departmentId;
for (var i = 0; i < usersList.length; i++) {
_emailId = usersList[i].emailId;
_userName = usersList[i].userName;
var params = {
TableName: "UsersTable",
Key: {
"emailId": _emailId,
"departmentId": _departmentId
}
};
docClient.get(params, function(err, data) {
if (!err) {
if (!data.items)
AddUserAndSendEmail("UsersTable", _emailId, _userName);
//The above function is being called twice but for the same user.
//It has a check so not inserting the same record twice but
//sending two mails to the same user.
}
});
}
res.end("success");
}
function AddUserAndSendEmail(tableName, emailId, _userName) {
var params = {
TableName: tableName,
Item: {
"emailId": emailId,
"departmentId": 101//Default Department
}
};
docClient.put(params, function(err, data) {
if (!err) {
//Send Email Code Here
} else {
console.log("error");
}
});
}
What could be the reason for this strange behavior? Really frustrated, I am about to give up on this.
1) Please note that DynamoDB is eventually consistent. If you insert the item and check whether the item exists immediately, it may not always find the item in the database.
This means the second iteration of the loop may not always find the first item inserted into the table.
2) If the item already exists in the table, the Put api will update the item and give successful response.
This means the Put will be successful for the same email id and department id in the second iteration because it updates the record if it is already present.
GetItem – The GetItem operation returns a set of Attributes for an
item that matches the primary key. The GetItem operation provides an
eventually consistent read by default. If eventually consistent reads
are not acceptable for your application, use ConsistentRead.
PutItem – Creates a new item, or replaces an old item with a new item
(including all the attributes). If an item already exists in the
specified table with the same primary key, the new item completely
replaces the existing item. You can also use conditional operators to
replace an item only if its attribute values match certain conditions,
or to insert a new item only if that item doesn’t already exist.
Based on the above points, there is a possibility to get two emails if you have same email id and department id in the array.
I need to create a view that lists the values for an attribute of a doc field.
Sample Doc:
{
"_id": "003e5a9742e04ce7a6791aa845405c17",
"title", "testdoc",
"samples": [
{
"confidence": "high",
"handle": "joetest"
}
]
}
Example using that doc, I want a view that will return the values for "handle"
I found this example with the heading - Get contents of an object with specific attributes e.g. doc.objects.[0].attribute. But when I fill in the attribute name, e.g. "handle" and replace doc.objects with doc.samples, I get no results:
Toggle line numbers
// map
function(doc) {
for (var idx in doc.objects) {
emit(doc.objects[idx], attribute)
}
}
That will create an array of key-value-pairs where the key is alway the value of handle. Replace null with a value you want e.g. doc.title. If you want to get the doc attached to every row use the query parameter ?include_docs=true while requesting the view.
// map
function (doc) {
var samples = doc.samples
for(var i = 0, sample; sample = samples[i++];) {
emit(sample.handle, null)
}
}
Like this ->
function(doc) {
for (var i in doc.samples) {
emit(doc._id, doc.samples[i].handle)
}
}
It will produce a result based on the doc._id field as the key. Or, if you want your key to be based on the .handle field you reverse the parameters in emit so you can search by startKey=, endKey=.
In my CouchDB database, all keys have the form "A_xxxxxxxx" where xxxxxxxx is zero-padded decimal number (e.g. "A_00000001" or "A_12345678")
I want to get only the number of keys in a given key range.
For example, to get the keys from A_10000000 to A_30000000, I can query something like:
GET DATABASE/_all_docs?startkey="A_00001000"&endkey="A_30000000"&include_docs=false
But the result contains all keys, and I need to count the elements in "docs" field of the output.
Since the number of keys in my query will be huge, and all I want to know is the number of keys, not the actual list of the keys.
The range start and range end value can be vary, which is not fixed.
Is is possible to get only the number of keys of the given range, without retrieving actual key list?
Thanks,
You cannot get the number of keys in a given key range using the built-in _all_docs view. But you can get the desired result using a custom map reduce view such as this one described in the CouchDB Definitive Guide
map.js
function(doc) {
emit(doc._id, 1);
}
reduce.js
function(keys, values, rereduce) {
return sum(values)
}
You can add these views to your CouchDB database using the Futon admin utility by creating a new document with these contents:
{
"_id": "_design/test",
"views": {
"count": {
"map": "function(doc) {\n emit(doc._id, 1);\n}",
"reduce": "function(keys, values, rereduce) {\n return sum(values)\n}"
}
}
}
_design/test/count can then be queried like instead of _all_docs and will return the number of documents between the start and end keys.
When I run this query again my database without a start and end key I get this result:
{
"rows":[
{
"key": null,
"value": 185
}
]
}
Running the query again with the start and end keys populated I get this result:
{
"rows":[
{
"key": null,
"value": 11
}
]
}
I am attempting to get a count of unique events for an object (lets say a video):
Here are my documents:
{
"type":"View",
"video_id": "12300",
"user_id": 3
}
{
"type":"View",
"video_id": "12300",
"user_id": 1
}
{
"type":"View",
"video_id": "45600",
"user_id": 3
}
I'm trying to get a unique (by user_id) count of views for each video
I assume I want to map my data like so:
function(doc) {
if (doc.type === 'View') {
emit([doc.video_id, doc.user_id], 1);
}
},
But I don't understand how to reduce it down to unique users per video, or am I going about this wrong.
You should look at the group_level view parameter. It will allow you to change what field(s) the grouping occurs on.
By using group_level = 1, in this case it will group by video_id. Using group_level = 2, it will group on both video_id and user_id.
Add ?group=true after the request URL. That groups identical keys together as input for the reduce function:
function(keys, values, rereduce){
return sum(values);
}
That should do it.
Note that keys and values are unzipped lists of keys and their values. With grouping on the keys are all identical for each call of the reduce.