Moved from GitHub dgraph/5335
Posted by MichelDiz:
Experience Report
What you wanted to do
I would like to use loops in queries and upsert blocks. In this case something similar to “foreach”.
What you actually did
There’s nothing similar to this in Dgraph right now.
Why that wasn’t great, with examples
A loop like foreach would be very useful. There are situations that we want to iterate over objects in a query. Whether to display a particular form structure in the response or to create specific mutations in the upsert block. Which is not currently supported in Dgraph.
Syntax
I believe that Syntax from foreach would be very similar to the K-shortest path.
More examples
I think a “foreach” func would be the solution for almost all the things like “groupby value”.
Ref of a DB doing something similar to it:
A foreach loop could solve this issue #4779 in a blink of an eye (eliminating the misuse of an extra block). I gonna add a comment there with an example using “foreach”.
see Bug with multi-level (nested bocks) in Upsert Block · Issue #4779 · dgraph-io/dgraph · GitHub
In this link FOREACH func in DQL (loops in Bulk Upsert) I have other use cases. Most of them related to upsert block, issues with Facets bad responses (e.g: #4160), and so on.
Pay attention that this link is a little old. I used different syntax just to illustrate.
Reference for the group by issue: Groupby does not support predicate of list type · Issue #4170 · dgraph-io/dgraph · GitHub
e.g: “for each group found in groupby create a new object to use in response”.
foreach(in: PARAM1, title: PARAM2).
> For each UID in PARAM1, create a new object in the response with the title in PARAM2
{
var(func: has(kind)) @groupby(kind) {
T as count(uid)
}
foreach(func: foreach(in: T, title: kind)) {
name
age
total : val(T)
}
}
Desirable Result
{
"data": {
"q": [
{
"dog": [
{
"total": 1
},
{
"uid": "0x1",
"name": "Bingo",
"age": "3"
}
]
},
{
"animal": [
{
"total": 2
},
{
"uid": "0x1",
"name": "Bingo",
"age": "3"
},
{
"uid": "0x3",
"name": "Angry Purr",
"age": "1"
}
]
},
{
"cat": [
{
"total": 1
},
{
"uid": "0x3",
"name": "Angry Purr",
"age": "1"
}
]
}
]
}
