Solving Common MongoDB Errors: Pitfalls for Beginners to Avoid

This article summarizes common mistakes and pitfalls for MongoDB beginners, with core content as follows: **1. Connection Issues**: Connection refusals often stem from the service not starting (use `systemctl` on Linux/Mac, or manually start on Windows), port occupation (default 27017; check with `netstat`), or incorrect connection strings (format: `mongodb://[host]:[port]/[database name]`). **2. Data Insertion**: Explicitly specify the collection (either use `use [database name]` or directly `db.[collection name].insertOne()`); avoid manually setting the `_id` to prevent duplicates, and rely on MongoDB's auto-generated unique keys. **3. Queries and Updates**: Ensure query condition types match (e.g., use string values for string fields); always include filter conditions in updates to avoid overwriting entire collections. **4. Data Types**: Despite "schema-less" design, maintain consistent field types (e.g., use `true/false` for booleans, `Date` type for dates) and avoid mixing numbers and strings. **5. Indexes and Other**: Repeated index creation wastes performance; use `getIndexes()` to check existing indexes. Version compatibility is critical (e.g., `$expr` requires MongoDB 3.2+).