當我嘗試聚合時
我正在使用這個 MongoDB 版本（“版本”：“5.0.4”）
{
$project: {
_id: 1,
feeling: 1,
updated_date: 1,
created_date: 1,
activity_type: 1,
activityCount: { $size: "$activity" },
activity_count: 1,
activity_tipped_count: 1,
activity_upvote_count: 1,
activity: { $last: "$activity" },
product: 1,
property: 1,
shared_post: 1,
post: 1,
user: 1,
rss_delete: 1,
},
},
它給出了這個錯誤
MongoError: Unrecognized expression '$last'
at Connection.<anonymous> (/Users/mac/Documents/WORK DISK/A PROJECTS/OutSourcing/Revstance-node-v3 /revstancev3/node_modules/mongodb/lib/core/connection/pool.js:453:61)
at Connection.emit (node:events:390:28)
at Connection.emit (node:domain:475:12)
at processMessage (/Users/mac/Documents/WORK DISK/A PROJECTS/OutSourcing/Revstance-node-v3 /revstancev3/node_modules/mongodb/lib/core/connection/connection.js:456:10)
at Socket.<anonymous> (/Users/mac/Documents/WORK DISK/A PROJECTS/OutSourcing/Revstance-node-v3 /revstancev3/node_modules/mongodb/lib/core/connection/connection.js:625:15)
at Socket.emit (node:events:390:28)
at Socket.emit (node:domain:475:12)
at addChunk (node:internal/streams/readable:315:12)
at readableAddChunk (node:internal/streams/readable:289:9)
at Socket.Readable.push (node:internal/streams/readable:228:10)
at TCP.onStreamRead (node:internal/stream_base_commons:199:23) {
ok: 0,
code: 168,
codeName: 'InvalidPipelineOperator'
}
在此先感謝任何幫助對我來說意義重大
uj5u.com熱心網友回復：
我猜這是驅動程式未能區分 $last 聚合累加器和 $arrayElemAt(-1) 的 $last 別名。根據https://docs.mongodb.com/manual/reference/operator/aggregation/last/上的檔案，累積運算子在 $project 階段無效。
也許嘗試用這個替換它：
activity: { $arrayElemAt: [ "$activity", -1 ] }
轉載請註明出處，本文鏈接：https://www.uj5u.com/gongcheng/424007.html
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