IssueTracker

Hi,

This looks really bad but w/o a repro app, we really cannot do anything about it. Is it possible for you to provide a sample app that reproduces your problem ?

Attached is a simple testing app. It inserts 10000 items into the db when activity starts and then displays them using paging. The db is also updated every 1 second. On the screen, if you drag the fast scroll bar up and down quickly a few times, it will eventually crash with this IndexOutOfBoundsException error.

Thanks for the great repro case, tracked it down, investigating a fix.

Problematic behavior:
1) AsyncPagedListDiffer receives new list, takes snapshot for diffing (ui thread)
2) At roughly the same time:
   2a) Diff snapshot of old snapshot vs new snapshot (bg thread)
   2b) New data arrives in new list, way earlier in the list, so the list is essentially: new page, lots of empty pages, initial load
3) AsyncPagedListDiffer updates lastLoad position with diffutil position mapping

In 3, we try to map the lastLoad position from old snapshot to new snapshot, but fail to distinguish between new list vs new snapshot. Because of all the empty pages, that's a huge discrepancy. This is why the huge scrollbar + lots of swaps triggers this well - there are lots of swaps to new PagedLists while loads are happening very far away from initial load positions.

Will need to account for pages loaded in between time of snapshot, and time of swap.

Fixed with https://android-review.googlesource.com/c/platform/frameworks/support/+/758685

Unfortunately, I don't have a workaround, will try and get this released shortly.

Awesome! Can not wait for the fix to drop.

I saw a new WorkManager version was dropped today but no new paging. Any ideas when this fix will be released? Days or weeks? Thanks.

no promises but it is already scheduled so should be days hopefully.

Released with Paging 2.0.0

Thanks for the update. Is 2.1.0-alpha02 around the corner?

Project: platform/frameworks/support
Branch: androidx-master-dev

commit 8e46b9ca1f55b040a18dd86833880b5106d103b2
Author: Daniel Santiago Rivera <danysantiago@google.com>
Date:   Wed Oct 10 19:17:50 2018

    Update Room's ANTLR Parser to 4.7.1
   
    Updating to the latest ANTLR version fixes the performance issue
    described in https://github.com/antlr/antlr4/issues/1398 which affects
    Room's SQL Parser since it contains left-recursive rules. Specifically
    SQLite.g4 has multiple recursions to describe an expression as defined
    in https://www.sqlite.org/lang_expr.html, meaning if a user has certain
    queries that causes the parser to use the adaptivePredict algorithm
    then the build time increases significantly due to Room's query
    parsing.
   
    Also bumped Room's version to 2.1.0-alpha02
   
    Bug: 117401230
    Test: ./gradlew room:integration-tests:testapp:cC
    Change-Id: I4d0799a11ccee816ab209cbf74e7dcf2b2ce1a18

M       buildSrc/src/main/kotlin/androidx/build/LibraryVersions.kt
M       buildSrc/src/main/kotlin/androidx/build/dependencies/Dependencies.kt
M       room/integration-tests/testapp/src/androidTest/java/androidx/room/integration/testapp/dao/UserDao.java

https://android-review.googlesource.com/786077
https://goto.google.com/android-sha1/8e46b9ca1f55b040a18dd86833880b5106d103b2

No concrete date on 2.1.0-alpha02, I want to get a few more bugs in before making the next alpha release. So maybe by the end of the month.

Thanks.

On Tue, Oct 16, 2018, 4:52 AM <buganizer-system@google.com> wrote:

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- Ankit