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Description

This error indicates that an operation attempted to use data with an incompatible BSON type. It typically occurs when querying, inserting, or updating documents where a field's value does not match the expected or existing data type.

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Error Message

Type Mismatch

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Known Causes

4 known causes

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Mismatched Query Types

Attempting to query a document field using a value of a different BSON data type than stored, leading to comparison failures.

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Inconsistent Data Operations

Inserting or updating a document field with a value whose BSON type differs from the expected or previously stored type.

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Aggregation Pipeline Type Issues

An aggregation pipeline stage receives or produces data types that are incompatible with subsequent operations or expected outputs.

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Schema Validation Violations

An operation attempts to modify or insert data that violates the BSON type constraints specified in a collection's schema validation rules.

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Solutions

4 solutions available

1. Use Correct Type in Query easy

Match data type stored in document

1

Check document structure

db.users.findOne()

2

Query with correct type

// If age is stored as number:
db.users.find({ age: 30 })  // Not { age: "30" }

// If date is stored as Date:
db.users.find({ created: new Date("2024-01-15") })  // Not string

2. Convert Types in Update medium

Fix inconsistent types in existing data

1

Convert string to number

db.users.updateMany(
  { age: { $type: "string" } },
  [{ $set: { age: { $toInt: "$age" } } }]
);

2

Convert string to date

db.events.updateMany(
  { date: { $type: "string" } },
  [{ $set: { date: { $toDate: "$date" } } }]
);

3. Fix Aggregation Type Errors medium

Handle type mismatches in pipeline

1

Use $convert for safe conversion

db.users.aggregate([
  {
    $project: {
      age: {
        $convert: {
          input: "$age",
          to: "int",
          onError: 0,
          onNull: 0
        }
      }
    }
  }
]);

4. Check for Mixed Types easy

Find documents with wrong types

1

Find documents with specific type

// Find where age is string instead of number:
db.users.find({ age: { $type: "string" } })

// BSON type numbers:
// 1 = double, 2 = string, 3 = object, 4 = array
// 9 = date, 10 = null, 16 = int, 18 = long

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Related Errors

5 related errors

MongoDB Error 14: Data Type Mismatch