Iterating Firestore Android collection on basis of ID or attribute

Question

I want to iterate a collection which starts at collection document ID.

Is there any method like below which let us read data start at an id or an attribute id?

 db.collection("questions").startReadingDocumentAt("02cubnmO1wqyz6yKg571 ").limit(10).get()

or

db.collection("questions").startReadingWhereEqualTo("questionID","02cubnmO1wqyz6yKg571 ").limit(10).get()

I know I can read that DocumentSnapShot on basis of Id and can then start iterating with lastVisible item. but it cost me two read operation. Can it be done in one.

Firestore-root
    |
    --- questions (collections)
    |     |
    |     --- 02cubnmO1wqyz6yKg571 (questionId document) // myID and my questionID is same
    |            |
    |            --- questionId: "02cubnmO1wqyz6yKg571"
    |            |
    |            --- title: "Question Title"
    |            |
    |            --- date: August 27, 2018 at 6:16:58 PM UTC+3
    |            |

I already have gone through this

Explanation

I don't want to do RecyclerView pagination. I want to load next 10 question each time an Activity starts. So I call the query in the same manner but it requires me to save the DocumentSnapShot. So I decided to save the questionID and read data on basis of it...

score 1 · Accepted Answer · answered Aug 29 '18 at 08:39

1

There is no:

startReadingDocumentAt("02cubnmO1wqyz6yKg571")

nor

startReadingWhereEqualTo("questionID","02cubnmO1wqyz6yKg571")

In firestore but according to your database schema, to solve this, you can use the following query:

db.collection("questions").
    whereGreaterThanOrEqualTo("questionID","02cubnmO1wqyz6yKg571")
    .limit(10)
    .get()
    addOnCompleteListener.(/* ... */)

More informations here:

Creates and returns a new Query with the additional filter that documents must contain the specified field and the value should be greater than or equal to the specified value.

answered Aug 29 '18 at 08:39

Alex Mamo

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yes I appreciate but one issue is remaining in https://stackoverflow.com/a/52040609/3496570 – Zar E Ahmer Aug 30 '18 at 11:31
@XarEAhmer Which is? I already commented on your last comment. – Alex Mamo Aug 30 '18 at 11:32

score 1 · Answer 2 · answered Sep 24 '18 at 21:25

1

You can do this using query cursors. E.g.:

db.collection("questions")
    .orderBy("questionID")
    .startAt("02cubnmO1wqyz6yKg571")
    .limit(10)
    .get()

answered Sep 24 '18 at 21:25

Michael Lehenbauer

16,031
1
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Iterating Firestore Android collection on basis of ID or attribute

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