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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: None
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Labels:None
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Fully Compatible
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178
Implement the appropriate query rewrite the 2 remaining cases with {+-meta, +ts}. Assuming that we extend the indexes to both (min,max) and (max,min) the rewrites become:
For reference, here's the case we already did in Milestone :2
index({meta.sensorId: 1, meta.sensorId: -1})
db.telemetry.aggregate([
{$sort: {"metadata.sensorId": 1, "timestamp": -1}},
{$group: {
_id: "$metadata.sensorId",
ts: {$first: "$timestamp"},
temp: {$first: "$temp"}
}}
])
translates to:
db.system.buckets.telemetry.explain("executionStats").aggregate([
{$sort: {"meta.sensorId": 1, "control.max.timestamp": -1}},
{$group: {
_id: "$meta.sensorId",
bucket: {$first: "$_id"},
}},
{$lookup: {
from: "system.buckets.telemetry",
foreignField: "_id",
localField: "bucket",
as: "bucket_data",
pipeline:[
{$_internalUnpackBucket: {
timeField:"timestamp",
metaField:"tags",
bucketMaxSpanSeconds:NumberInt("60")
}},
{$sort: {"timestamp": -1}},
{$limit:1}
]
}},
{$unwind: "$bucket_data"},
{$replaceWith:{
_id: "$_id",
timestamp: "$bucket_data.timestamp",
temp: "$bucket_data.temp"
}}
]);
This is adapted as follows:
| milestone | user index | $sort | $group accumulator |
|---|---|---|---|
| 2 (done) | {meta:1, ts:-1} | {meta:1, control.max.timestamp:-1} | $first |
| 3 | {meta:-1, ts:-1} | {meta:-1, control.max.timestamp:-1} | $first |
| 3 | {meta:1, ts:1} | {meta:1, control.max.timestamp:1} | $last |
| 3 | {meta:-1, ts:1} | {meta:-1, control.max.timestamp:1} | $last |
This tickets covers the last two rows above.
- related to
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- Closed
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