database config_error ai_generated true

MongoServerError: Cannot create index 'idx_email_unique': a unique index on field 'email' already exists with different options

ID: database/mongodb-cannot-create-index-duplicate-key

Also available as: JSON · Markdown · 中文
90%Fix Rate
85%Confidence
1Evidence
2023-09-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
MongoDB 5.0 active — — —
MongoDB 6.0 active — — —
MongoDB 7.0 active — — —
MongoDB 8.0 active — — —

Root Cause

An existing unique index on the same field has different options (e.g., collation, sparse, partial filter expression) than the new index being created, causing a conflict.

generic

中文

同一字段上已存在的唯一索引与新创建的索引具有不同的选项（例如，排序规则、稀疏、部分过滤器表达式），导致冲突。

Official Documentation

https://www.mongodb.com/docs/manual/reference/method/db.collection.createIndex/

Workarounds

  1. 90% success List existing indexes on the collection: `db.collection.getIndexes()`. Identify the conflicting index and drop it: `db.collection.dropIndex('idx_email_unique')`. Then create the new index with the desired options: `db.collection.createIndex({email: 1}, {unique: true, name: 'idx_email_unique', collation: {locale: 'en', strength: 2}})` 
    List existing indexes on the collection: `db.collection.getIndexes()`. Identify the conflicting index and drop it: `db.collection.dropIndex('idx_email_unique')`. Then create the new index with the desired options: `db.collection.createIndex({email: 1}, {unique: true, name: 'idx_email_unique', collation: {locale: 'en', strength: 2}})`
  2. 85% success If the existing index has different options but you want to keep it, rename the new index to a different name: `db.collection.createIndex({email: 1}, {unique: true, name: 'idx_email_unique_v2'})` 
    If the existing index has different options but you want to keep it, rename the new index to a different name: `db.collection.createIndex({email: 1}, {unique: true, name: 'idx_email_unique_v2'})`

中文步骤

  1. 列出集合上的现有索引：`db.collection.getIndexes()`。识别冲突索引并删除它：`db.collection.dropIndex('idx_email_unique')`。然后使用所需选项创建新索引：`db.collection.createIndex({email: 1}, {unique: true, name: 'idx_email_unique', collation: {locale: 'en', strength: 2}})`
  2. 如果现有索引具有不同选项但您想保留它，将新索引重命名为不同名称：`db.collection.createIndex({email: 1}, {unique: true, name: 'idx_email_unique_v2'})`

Dead Ends

Common approaches that don't work:

  1. Drop the existing index with db.collection.dropIndex() and recreate it with the same name but different options 50% fail

    If the existing index is being used by an application, dropping it may cause query performance degradation or application errors until the new index is created

  2. Create the index with the force: true option 100% fail

    MongoDB does not support a 'force' option for index creation; this will result in a syntax error

  3. Ignore the error and assume the index already exists 60% fail

    The existing index may have different collation or options, leading to unexpected behavior in queries or uniqueness enforcement