android - Paging 3 - Does Room drop pages even if maxSize is MAX_SIZE_UNBOUNDED?

Question

I'm using Paging 3 with Room and RemoteMediator. I haven't set a maxSize in the PagingConfig which means that we shouldn't drop pages no matter how far we scroll.

fun getSearchResults(query: String): Flow<PagingData<NewsArticle>> =
        Pager(
            config = PagingConfig(pageSize = 50),
            remoteMediator = SearchNewsRemoteMediator(query, newsArticleDatabase, newsApi),
            pagingSourceFactory = { newsArticleDao.getSearchResultArticlesPaged(query) }
        ).flow

However, I noticed that Room still drops pages when I scroll far enough. I observed that in logcat via an AdapterDataObserver.

onItemRangeRemoved start: 100 count: 100 end: 199

My question is: Is this expected behavior, or a bug, or some error on my side? If it's expected behavior, what is the maxSize attribute for? I observed my data with a maxSize value set but it never removed any entries from the database.

Edit: I now also noticed that Room does not drop pages if we are looking at cached offline data. Why? I would expect it to behave exactly the same.

question from:https://stackoverflow.com/questions/65898009/paging-3-does-room-drop-pages-even-if-maxsize-is-max-size-unbounded

Answer 1

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