{
  "id": "mongodb/index-build-failed-due-to-duplicate-keys",
  "signature": "MongoServerError: Index build failed: collection mydb.mycoll has duplicate keys for index 'unique_idx'",
  "signature_zh": "MongoServerError: 索引构建失败：集合 mydb.mycoll 在索引 'unique_idx' 上存在重复键",
  "regex": "Index build failed.*has duplicate keys for index",
  "domain": "mongodb",
  "category": "data_error",
  "subcategory": null,
  "root_cause": "An attempt to create a unique index failed because the collection contains documents with duplicate values for the indexed field(s).",
  "root_cause_type": "generic",
  "root_cause_zh": "尝试创建唯一索引失败，因为集合包含索引字段的重复值。",
  "versions": [
    {
      "version": "MongoDB 6.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "MongoDB 7.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "MongoDB 8.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "The same duplicates still exist in the collection.",
      "fail_rate": 1.0,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "dropDups is removed in MongoDB 4.0+; in older versions, it deletes arbitrary duplicates.",
      "fail_rate": 0.9,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Sparse indexes still enforce uniqueness on non-null values, so duplicates remain.",
      "fail_rate": 0.8,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Identify duplicate documents using aggregation: db.mycoll.aggregate([ { $group: { _id: '$field', count: { $sum: 1 } } }, { $match: { count: { $gt: 1 } } } ]). Then delete or update duplicates.",
      "success_rate": 0.9,
      "how": "Identify duplicate documents using aggregation: db.mycoll.aggregate([ { $group: { _id: '$field', count: { $sum: 1 } } }, { $match: { count: { $gt: 1 } } } ]). Then delete or update duplicates.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Use db.collection.createIndex() with { unique: true, partialFilterExpression: { field: { $exists: true } } } to skip documents missing the field if duplicates are only on missing values.",
      "success_rate": 0.85,
      "how": "Use db.collection.createIndex() with { unique: true, partialFilterExpression: { field: { $exists: true } } } to skip documents missing the field if duplicates are only on missing values.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Create a non-unique index first, then manually deduplicate data and rebuild the unique index.",
      "success_rate": 0.8,
      "how": "Create a non-unique index first, then manually deduplicate data and rebuild the unique index.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Identify duplicate documents using aggregation: db.mycoll.aggregate([ { $group: { _id: '$field', count: { $sum: 1 } } }, { $match: { count: { $gt: 1 } } } ]). Then delete or update duplicates.",
    "Use db.collection.createIndex() with { unique: true, partialFilterExpression: { field: { $exists: true } } } to skip documents missing the field if duplicates are only on missing values.",
    "Create a non-unique index first, then manually deduplicate data and rebuild the unique index."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": null,
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.87,
  "fix_success_rate": 0.9,
  "resolvable": "true",
  "first_seen": "2023-06-05",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}