Firestore Composite Index Sort Not Modifying Order

Question

Issue

The order of the data returned is not changing using a Firestore multiple attribute composite index sort. This is compared to the original sort performed on one attribute. Currently, the data is returned being only sorted by timestamp with and without the composite index applied.

Expected

The data should sort in terms of the qualityScore attribute when using the composite index of the timestamp and qualityScore.

Implementation

The query results are consumed by the FirestorePagingOptions.Builder<Content>() method setQuery().

val options: FirestorePagingOptions<Content> = FirestorePagingOptions.Builder<Content>()
            .setLifecycleOwner(this)
            .setQuery(viewModel.contentFeedQuery, config, Content::class.java).build()

I'm reading the results from the onBindViewHolder of the FirestorePagingAdapter.

override fun onBindViewHolder(viewHolder: ViewHolder, position: Int, content: Content) {
            println("QUALITY_SCORE: " + content.timestamp + " " + content.qualityScore)
            viewHolder.bind(content)
        }

Original Sort

return FirestoreCollections.contentCollection
.collection(ALL_COLLECTION)
.orderBy(TIMESTAMP, DESCENDING)
.whereGreaterThanOrEqualTo(TIMESTAMP,getTimeframe(WEEK))  

Result

2018-08-26 01:15:08.548 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 15:17:26 PDT 2018 17.0
2018-08-26 01:15:08.574 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 13:30:44 PDT 2018 17.0
2018-08-26 01:15:11.698 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 11:16:47 PDT 2018 16.0
2018-08-26 01:15:11.728 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 08:09:52 PDT 2018 18.0
2018-08-26 01:15:11.777 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 07:38:36 PDT 2018 21.0
2018-08-26 01:15:11.804 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 06:16:23 PDT 2018 20.0
2018-08-26 01:15:11.849 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Thu Aug 23 15:39:59 PDT 2018 15.0
2018-08-26 01:15:11.890 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Thu Aug 23 07:23:51 PDT 2018 1.0
2018-08-26 01:15:11.915 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Wed Aug 22 16:15:02 PDT 2018 5.0
2018-08-26 01:15:11.947 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Wed Aug 22 08:00:12 PDT 2018 22.0
2018-08-26 01:15:12.000 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Tue Aug 21 17:28:03 PDT 2018 19.0
2018-08-26 01:15:12.050 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Tue Aug 21 08:59:06 PDT 2018 6.0
2018-08-26 01:15:12.115 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Tue Aug 21 08:17:53 PDT 2018 7.0
2018-08-26 01:15:12.167 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Mon Aug 20 22:40:56 PDT 2018 9.0
2018-08-26 01:15:12.235 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Mon Aug 20 06:58:18 PDT 2018 10.0
2018-08-26 01:15:12.318 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Mon Aug 20 04:07:27 PDT 2018 12.0
2018-08-26 01:15:12.367 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Sun Aug 19 21:08:31 PDT 2018 8.0
2018-08-26 01:15:12.410 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Sun Aug 19 15:11:37 PDT 2018 14.0
2018-08-26 01:15:12.449 27668-27668/app.carpecoin I/System.out: QUALITY_SCORE: Sun Aug 19 03:35:52 PDT 2018 200.0

Composite Index Sort

return FirestoreCollections.contentCollection
.collection(ALL_COLLECTION)
.orderBy(TIMESTAMP, DESCENDING)
.orderBy(QUALITY_SCORE, DESCENDING)
.whereGreaterThanOrEqualTo(TIMESTAMP,getTimeframe(WEEK))  

Result

2018-08-26 01:13:54.549 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 15:17:26 PDT 2018 17.0
2018-08-26 01:13:54.579 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 13:30:44 PDT 2018 17.0
2018-08-26 01:13:58.110 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 11:16:47 PDT 2018 16.0
2018-08-26 01:13:58.205 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 08:09:52 PDT 2018 18.0
2018-08-26 01:13:58.339 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 07:38:36 PDT 2018 21.0
2018-08-26 01:13:58.420 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Fri Aug 24 06:16:23 PDT 2018 20.0
2018-08-26 01:13:58.590 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Thu Aug 23 15:39:59 PDT 2018 15.0
2018-08-26 01:13:58.840 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Thu Aug 23 07:23:51 PDT 2018 1.0
2018-08-26 01:13:58.940 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Wed Aug 22 16:15:02 PDT 2018 5.0
2018-08-26 01:13:59.041 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Wed Aug 22 08:00:12 PDT 2018 22.0
2018-08-26 01:13:59.183 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Tue Aug 21 17:28:03 PDT 2018 19.0
2018-08-26 01:13:59.360 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Tue Aug 21 08:59:06 PDT 2018 6.0
2018-08-26 01:13:59.427 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Tue Aug 21 08:17:53 PDT 2018 7.0
2018-08-26 01:13:59.467 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Mon Aug 20 22:40:56 PDT 2018 9.0
2018-08-26 01:13:59.517 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Mon Aug 20 06:58:18 PDT 2018 10.0
2018-08-26 01:13:59.567 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Mon Aug 20 04:07:27 PDT 2018 12.0
2018-08-26 01:13:59.633 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Sun Aug 19 21:08:31 PDT 2018 8.0
2018-08-26 01:13:59.703 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Sun Aug 19 15:11:37 PDT 2018 14.0
2018-08-26 01:13:59.769 26943-26943/app.carpecoin I/System.out: QUALITY_SCORE: Sun Aug 19 03:35:52 PDT 2018 200.0

Composite Index Setup

I setup 2 composite indexes as I was testing various combinations in order to achieve a result of the data being returned sorted by qualityScore after a specific timestamp.

Answer 1

You call .orderBy(TIMESTAMP, DESCENDING).orderBy(QUALITY_SCORE, DESCENDING). This means that the documents are first ordered by descending timestamp, and when those are the same, they are ordered by descending quality score.

Since all documents in the result set have a unique timestamp, that is the only visible result. Only when multiple documents have the same value for the first sort field, does the second sort field become relevant.