[
https://issues.apache.org/jira/browse/FLINK-8790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16493578#comment-16493578
]
ASF GitHub Bot commented on FLINK-8790:
---------------------------------------
Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/5582#discussion_r191446316
--- Diff:
flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java
---
@@ -718,70 +718,63 @@ void restore(Collection<KeyedStateHandle>
restoreStateHandles) throws Exception
boolean hasExtraKeys = (restoreStateHandles.size() > 1
||
!Objects.equals(restoreStateHandles.iterator().next().getKeyGroupRange(),
stateBackend.keyGroupRange));
- if (hasExtraKeys) {
- stateBackend.createDB();
- }
-
- for (KeyedStateHandle rawStateHandle :
restoreStateHandles) {
-
- if (rawStateHandle instanceof
IncrementalKeyedStateHandle) {
-
restoreInstance((IncrementalKeyedStateHandle) rawStateHandle, hasExtraKeys);
- } else if (rawStateHandle instanceof
IncrementalLocalKeyedStateHandle) {
- Preconditions.checkState(!hasExtraKeys,
"Cannot recover from local state after rescaling.");
-
restoreInstance((IncrementalLocalKeyedStateHandle) rawStateHandle);
- } else {
- throw new
IllegalStateException("Unexpected state handle type, " +
- "expected " +
IncrementalKeyedStateHandle.class +
- ", but found " +
rawStateHandle.getClass());
- }
+ if (!hasExtraKeys) {
+
restoreFromSingleHandle(restoreStateHandles.iterator().next());
--- End diff --
This new (and also the old code before) look like there could be a
potential bug: if `restoreStateHandles.size() > 1` is false, how can we be sure
that `restoreStateHandles.iterator().next()` exists? Even if it works from some
hidden assumption, it does not look so clean.
> Improve performance for recovery from incremental checkpoint
> ------------------------------------------------------------
>
> Key: FLINK-8790
> URL: https://issues.apache.org/jira/browse/FLINK-8790
> Project: Flink
> Issue Type: Improvement
> Components: State Backends, Checkpointing
> Affects Versions: 1.5.0
> Reporter: Sihua Zhou
> Assignee: Sihua Zhou
> Priority: Major
> Fix For: 1.6.0
>
>
> When there are multi state handle to be restored, we can improve the
> performance as follow:
> 1. Choose the best state handle to init the target db
> 2. Use the other state handles to create temp db, and clip the db according
> to the target key group range (via rocksdb.deleteRange()), this can help use
> get rid of the `key group check` in
> `data insertion loop` and also help us get rid of traversing the useless
> record.
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