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Type:
New Feature
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Resolution: Fixed
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: Aggregation Framework
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Labels:
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Fully Compatible
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Query Execution 2021-02-22, Query Execution 2021-03-08, Query Execution 2021-03-22
The changes from 7d915a6 as part of SERVER-49895 made it so including {$_requestReshardingResumeToken: true} in the aggregation request would cause a {postBatchResumeToken: {ts: <latestOplogEntryTimestamp>}} to be included in the cursor response. However, the plumbing was only done in CollectionScan and therefore only applies when the pipeline can be entirely optimized away. PlanExecutorPipeline::_latestOplogTimestamp is only updated when PlanExecutorPipeline::_isChangeStream == true. This makes including {$_requestReshardingResumeToken: true} not useful when running more complex aggregations such as the one resharding is using to fetch donor shard's oplog entries.
Steps to reproduce
python buildscripts/resmoke.py run --suite=sharding jstests/sharding/resharding_oplog_sync_agg_resume_token.js
diff --git a/jstests/sharding/resharding_oplog_sync_agg_resume_token.js b/jstests/sharding/resharding_oplog_sync_agg_resume_token.js index 047a01abc8..3dbeb5d4d3 100644 --- a/jstests/sharding/resharding_oplog_sync_agg_resume_token.js +++ b/jstests/sharding/resharding_oplog_sync_agg_resume_token.js @@ -28,7 +28,9 @@ const localDb = rst.getPrimary().getDB("local"); jsTest.log("Run aggregation pipeline on oplog with $_requestReshardingResumeToken set"); const resEnabled = localDb.runCommand({ aggregate: "oplog.rs", - pipeline: [{$match: {ts: {$gte: Timestamp(0, 0)}}}], + // The $addFields prevents the pipeline from being optimized away as a simple plan executor. + // This is necessary to force the pipeline to be evaluated using PlanExecutorPipeline. + pipeline: [{$match: {ts: {$gte: Timestamp(0, 0)}}}, {$addFields: {extra: {$literal: "hi"}}}], $_requestReshardingResumeToken: true, cursor: {batchSize: 1} });
- is depended on by
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SERVER-49897 Insert no-op entries into oplog buffer collections for resharding so resuming is less wasteful
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- Closed
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- is related to
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- Closed
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SERVER-54857 Re-examine disposal approach of the inner PlanExecutor of DocumentSourceCursor
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- Closed
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