When checking for possible bucket rollover in `determineRolloverReason()`, we check for schema incompatibility, in particular for cases where we have
timeseriesBucketsMayHaveMixedSchemaData: false
We also have a check that can keep a bucket open for large measurements:
if (keepBucketOpenForLargeMeasurements) { if (bucket.size + sizesToBeAdded.total() > absoluteMaxSize) { if (absoluteMaxSize != Bucket::kLargeMeasurementsMaxBucketSize) { return RolloverReason::kCachePressure; } return RolloverReason::kSize; } // There's enough space to add this measurement and we're still below the large // measurement threshold. if (!bucket.keptOpenDueToLargeMeasurements) { // Only increment this metric once per bucket. bucket.keptOpenDueToLargeMeasurements = true; stats.incNumBucketsKeptOpenDueToLargeMeasurements(); } return RolloverReason::kNone; } else {
This check bails out of the rollover determination with RolloverReason::kNone immediately, which results in skipping remaining schema incompatibility checks. This was the cause of SERVER-105854, where a document with a mixed schema (different canonical type for the same field) was missed because the measurements are very large.
REMEDIATION AND WORKAROUNDS
If impacted, upgrade to a fixed version and set the timeseriesBucketsMayHaveMixedSchemaData to true for each affected collection to ensure that future queries on the collection return correct results.
For example:
db.runCommand({ collMod: coll, timeseriesBucketsMayHaveMixedSchemaData: true });
Please see the remediation steps provided in our support-tools repo for a complete step-by-step guide on how to resolve the impacted collections.
- is depended on by
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SERVER-105854 "Mixed schema" error while attempting to delete docs from a time series bucket
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- Closed
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- is related to
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- Closed
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- related to
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SERVER-111007 Validation should distinguish between root causes when finding mixed schema data
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- In Code Review
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- Closed
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SERVER-107377 Add jstests to exercise mixed schema data bucket rollover in timeseries
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- Closed
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