MQE: fix issue where a query with a common subexpression could return incorrect results #11989
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lamida
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Jul 7, 2025
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… incorrect results (#11989) #### What this PR does This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results. The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling `Remove` for the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values. #### Which issue(s) this PR fixes or relates to #11189 #### Checklist - [x] Tests updated. - [n/a] Documentation added. - [covered by #10067] `CHANGELOG.md` updated - the order of entries should be `[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry is not needed, please add the `changelog-not-needed` label to the PR. - [n/a] [`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md) updated with experimental features. (cherry picked from commit 8c9ffff)
mimir-github-bot bot
pushed a commit
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Jul 7, 2025
… incorrect results (#11989) #### What this PR does This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results. The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling `Remove` for the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values. #### Which issue(s) this PR fixes or relates to #11189 #### Checklist - [x] Tests updated. - [n/a] Documentation added. - [covered by #10067] `CHANGELOG.md` updated - the order of entries should be `[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry is not needed, please add the `changelog-not-needed` label to the PR. - [n/a] [`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md) updated with experimental features. (cherry picked from commit 8c9ffff)
mimir-github-bot bot
pushed a commit
that referenced
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Jul 7, 2025
… incorrect results (#11989) #### What this PR does This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results. The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling `Remove` for the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values. #### Which issue(s) this PR fixes or relates to #11189 #### Checklist - [x] Tests updated. - [n/a] Documentation added. - [covered by #10067] `CHANGELOG.md` updated - the order of entries should be `[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry is not needed, please add the `changelog-not-needed` label to the PR. - [n/a] [`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md) updated with experimental features. (cherry picked from commit 8c9ffff)
mimir-github-bot bot
pushed a commit
that referenced
this pull request
Jul 7, 2025
… incorrect results (#11989) #### What this PR does This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results. The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling `Remove` for the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values. #### Which issue(s) this PR fixes or relates to #11189 #### Checklist - [x] Tests updated. - [n/a] Documentation added. - [covered by #10067] `CHANGELOG.md` updated - the order of entries should be `[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry is not needed, please add the `changelog-not-needed` label to the PR. - [n/a] [`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md) updated with experimental features. (cherry picked from commit 8c9ffff)
mimir-github-bot bot
pushed a commit
that referenced
this pull request
Jul 7, 2025
… incorrect results (#11989) #### What this PR does This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results. The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling `Remove` for the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values. #### Which issue(s) this PR fixes or relates to #11189 #### Checklist - [x] Tests updated. - [n/a] Documentation added. - [covered by #10067] `CHANGELOG.md` updated - the order of entries should be `[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry is not needed, please add the `changelog-not-needed` label to the PR. - [n/a] [`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md) updated with experimental features. (cherry picked from commit 8c9ffff)
mimir-github-bot bot
pushed a commit
that referenced
this pull request
Jul 7, 2025
… incorrect results (#11989) #### What this PR does This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results. The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling `Remove` for the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values. #### Which issue(s) this PR fixes or relates to #11189 #### Checklist - [x] Tests updated. - [n/a] Documentation added. - [covered by #10067] `CHANGELOG.md` updated - the order of entries should be `[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry is not needed, please add the `changelog-not-needed` label to the PR. - [n/a] [`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md) updated with experimental features. (cherry picked from commit 8c9ffff)
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The backport to To backport manually, run these commands in your terminal: # Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-11989-to-release-2.17 origin/release-2.17
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 8c9fffff376a6433f9d5713cdf88ee757ab4397e
# Push it to GitHub
git push --set-upstream origin backport-11989-to-release-2.17
git switch main
# Remove the local backport branch
git branch -D backport-11989-to-release-2.17Then, create a pull request where the |
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Backport to 2.17 isn't necessary, as the release is based on the r350 branch and this fix was already backported there. |
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What this PR does
This PR fixes an issue where common subexpression elimination (CSE) can cause a query to return incorrect query results.
The issue would occur if the ring buffer used to buffer data was in a state where the head of the buffer is at the end of the slice, and the tail was at the beginning of the slice. In this case, calling
Removefor the item at the end of the slice would return the correct value, as would the subsequent call for the item at the beginning of the slice, but all following calls would return incorrect values.Which issue(s) this PR fixes or relates to
#11189
Checklist
CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX]. If changelog entry is not needed, please add thechangelog-not-neededlabel to the PR.about-versioning.mdupdated with experimental features.