Hi everyone
I was trying to retrieve all occurrences of a headline field in my collection but I got only an array of my headlines. Could you tell me if it is possible to get an string of this array?
Below my pipeline:
[{$match: {
dtNews:{$gt: "2019-10-01"}
}}, {$project: {
str_title:1
}}, {$group: {
_id: null,
tex: {
$addToSet: "$str_title"
}
}}]
Ezequias.
Could you please give us an sample document?
[{
$match: {
dtNews: {
$gt: "2019-10-01"
}
}
} {
"$group": {
"_id": {
"__alias_0": "$str_title"
},
"__alias_1": {
"$sum": 1
}
}
},
{
"$project": {
"_id": 0,
"__alias_0": "$_id.__alias_0",
"__alias_1": 1
}
},
{
"$project": {
"text": "$__alias_0",
"size": "$__alias_1",
"_id": 0
}
}
]I have sample news documents like this:
{ _id: 1, title: "hello world", content: "some content 1" },
{ _id: 2, title: "Hello World", content: "some content 2" },
{ _id: 3, title: "Wonderful World", content: "some content 3" },
{ _id: 4, title: "Lovely World", content: "some content 4" }
and, using this aggregation query:
db.news.aggregate( [
{
$group: {
_id: null,
titlesArr: { $push: "$title" }
}
},
{
$project: {
_id: 0,
tex: {
$reduce: {
input: "$titlesArr",
initialValue: "",
in: {
$concat : ["$$value", "$$this", " "]
}
}
}
}
}
] )
I get this result:
{ "tex" : "hello world Hello World Wonderful World Lovely World " }
I think I misunderstood you before, looks like you are looking for distinct values;
db.getCollection("news").distinct("title");
result:
[
"Hello World",
"Lovely World",
"Wonderful World",
"hello world"
]
Is this the output you are looking for?
Thank you so much. It worked perfectly.
Dear @Prasad_Saya
Your solution was perfect. I don’t know if it is appropriate to ask here but I would like to know why this concatenation does not appears in MongoDB Compass Agregation tab (not even in a view).
Could you give me some advice?
I meant with large dataset. With your data sample it appears ok but with more information the presentation at Compass does not show full data.
I can only see it at console mode.
Sincerely
Ezequias Rocha
With a larger data set (about 10,000 documents) I found that in the Compass’s Aggregation, the $group stage output showed all data. But, the $project stage’s result view showed only first few words of the text, as in the attached picture.
I am using MongoDB version 4.2 and Compass 1.19.
Have you try disabling the “SAMPLE MODE” and “AUTO PREVIEW” options. May be it does that to make building the pipeline more responsive.
I am using 1.20.5 and the visualization isn’t also not so ok.
I noticed that if I create a view of this agregation I could see it in the second type of visualization as you can see below:
I think it is a solution but it would wrap text if it gets over 200 columns.
Sincerely
Ezequias Rocha
Thank you @coderkid I was trying to get only one string with all words collected. I already get the correct agregation.
Best regards
Ezequias
If you look at the screenshot of Prasad_Saya you will see two options at the right almost at the top.
