only set MinSafeTS to 0 when all stores' are 0 #1284
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Signed-off-by: zyguan <[email protected]>
cfzjywxk
reviewed
Apr 10, 2024
| minSafeTS = safeTS | ||
| } | ||
| } else { | ||
| minSafeTS = 0 | ||
| } | ||
| } | ||
| // if minSafeTS is still math.MaxUint64, that means all store safe ts are 0, then we set minSafeTS to 0. | ||
| if minSafeTS == math.MaxUint64 { | ||
| minSafeTS = 0 |
There was a problem hiding this comment.
Or could we set it to something like safepoint ts ?
There was a problem hiding this comment.
Sound reasonable, let me think about if it would break some constraints.
There was a problem hiding this comment.
It seem minSafeTS=0 and minSafeTS=safepoint are somehow equivalent here. The minSafeTS is exported by KVStore.GetMinSafeTS and used for reading history data (stale read & flashback in tidb). safepoint <= read ts < min safe ts is required for this usage. So:
- if we set min safe ts to 0 constantly,
read ts < min safe tscannot be satisfied, which should lead to errors like 'invalid read ts' or 'wait timeout'. - if we set min safe ts to safepoint,
safepoint <= read ts < min safe tsare also always false, then the read should be forbidden as well.
IMO, it's ok to set it to 0, since setting it to safepoint doesn't make any difference.
Defined2014
approved these changes
Apr 10, 2024
you06
reviewed
Apr 10, 2024
cfzjywxk
approved these changes
Apr 18, 2024
Signed-off-by: zyguan <[email protected]>
Merged
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
#1277 introduce a regression: there might be a store whose safe ts is 0 for a long time, in this case, flashback will be blocked (ref: tikv/tikv#13675). We should
setMinSafeTS(0)only when all (NOT any) ofstore.safe_ts = 0.