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Type:
Bug
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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: None
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Query Integration
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Minor Change
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ALL
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v7.0
When running an aggregation with a $documents stage, the query shape comes from a rewritten query that is unique each time the query runs. The pipeline in the query shape looks like this, with different UUIDs each time the query runs:
{
"$queue" : "?array<?object>"
},
{
"$project" : {
"_id" : true,
"03e7f159-305d-4009-9eb8-37f849cb26cb" : "?array<?object>"
}
},
{
"$unwind" : {
"path" : "$03e7f159-305d-4009-9eb8-37f849cb26cb"
}
},
{
"$replaceRoot" : {
"newRoot" : "$03e7f159-305d-4009-9eb8-37f849cb26cb"
}
}
The script below runs such a query twice (run with ./mongo --nodb example.js or using resmoke.py). After running it, search in the output for Query Stats: and notice that there are two entries with distinct query shapes.
const options = {setParameter: {internalQueryStatsRateLimit: -1}}; const conn = MongoRunner.runMongod(options); const testDB = conn.getDB("test"); const coll = testDB.coll; assert.commandWorked(coll.insert([{v: 1, y: -3}, {v: 2, y: -2}])); { const pipeline = [ {$documents: [{v:1}, {v:2}]}, {$lookup: { from: coll.getName(), as: "lookedUp", localField: "v", foreignField: "v"} }, ]; const cmd = { aggregate: 1, pipeline: pipeline, cursor: {}, }; // Run twice to see if the query shape differs each time assert.commandWorked(testDB.runCommand(cmd)); assert.commandWorked(testDB.runCommand(cmd)); const result = conn.adminCommand({ aggregate: 1, pipeline: [ {$queryStats: {}}, {$sort: {key: 1}}, {$match: {"key.client.application.name": "MongoDB Shell"}} ], cursor: {} }); assert.commandWorked(result); print("Query Stats: " + tojson(result.cursor.firstBatch)); } MongoRunner.stopMongod(conn);