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Description

This error occurs in MongoDB when an aggregation pipeline stage contains an operator that is not recognized or is used incorrectly. It typically indicates a syntax error, a misspelled operator name, or an attempt to use an operator not supported in the current MongoDB version or context.

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Error Message

Invalid Pipeline Operator

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Known Causes

4 known causes

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Misspelled Operator Name

A common cause is a typo or misspelling of an aggregation pipeline operator, leading MongoDB to not recognize it.

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Non-existent or Deprecated Operator

The pipeline includes an operator that does not exist in the current MongoDB version or has been deprecated and removed.

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Incorrect Operator Context

An operator is used in an aggregation stage where it is not valid, such as using a document operator directly in a top-level stage.

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Invalid Operator Syntax

While the operator name might be correct, its arguments or structure violate the expected syntax, making it invalid.

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Solutions

4 solutions available

1. Correcting Typographical Errors in Aggregation Pipeline Operators easy

Identify and fix simple typos in your aggregation pipeline stages.

1

Carefully review the aggregation pipeline code for any spelling mistakes in the operator names. Common errors include missing letters, extra letters, or incorrect capitalization.

db.collection.aggregate([
  { $match: { status: 'active' } },
  { $group: { _id: '$category', count: { $sum: 1 } } }, // Ensure '$sum' is spelled correctly
  { $sort: { count: -1 } } // Ensure '$sort' is spelled correctly
]);

2

Compare the operator names in your code against the official MongoDB aggregation pipeline operator documentation to ensure accuracy. Pay close attention to the '$' prefix.

Example: Instead of `$grop`, use `$group`. Instead of `$sum: 1`, ensure it's exactly `$sum: 1`.

2. Verifying Supported Aggregation Operators for MongoDB Version medium

Ensure the aggregation operators you are using are supported by your MongoDB version.

1

Determine the exact version of your MongoDB deployment. You can find this by running `db.version()` in the mongo shell or checking your deployment configuration.

db.version();

2

Consult the official MongoDB documentation for your specific version to verify the availability of the aggregation pipeline operators you are using. Newer operators might not be available in older versions.

Navigate to the MongoDB documentation website and select the version corresponding to your deployment. Search for 'Aggregation Pipeline' and review the list of available operators.

3

If an operator is not supported in your version, consider upgrading your MongoDB deployment or refactoring your aggregation pipeline to use alternative operators that are compatible with your current version.

For example, if you are using a newer operator in MongoDB 4.0 and your deployment is on 3.6, you might need to find an older way to achieve the same result.

3. Checking for Incorrect Operator Usage or Syntax medium

Identify and correct syntax errors or improper usage of aggregation operators.

1

Examine the arguments and structure of each aggregation operator. Some operators require specific data types or nested structures.

Incorrect: `{ $project: { fullName: '$firstName' + ' ' + '$lastName' } }`
Correct: `{ $project: { fullName: { $concat: ['$firstName', ' ', '$lastName'] } } }`

2

Ensure that field names are correctly referenced using the '$' prefix (e.g., '$fieldName').

Incorrect: `{ $match: { status: 'active' } }` (if 'status' is a field name)
Correct: `{ $match: { '$status': 'active' } }` (if 'status' is a field name)

3

Validate that nested operators are correctly placed and have the expected arguments. For instance, `$sum` within `$group` should be a field accumulator.

Incorrect: `{ $group: { _id: '$category', count: '$sum' } }`
Correct: `{ $group: { _id: '$category', count: { $sum: 1 } } }`

4

Use the MongoDB shell's auto-completion and syntax highlighting to help identify potential issues as you type your aggregation queries.

Type `$match` and press Tab to see available options.

4. Ensuring Correct Field Names and Data Types for Operators medium

Verify that the fields you are referencing in your pipeline exist and have the expected data types.

1

Inspect the schema or sample documents of your collection to confirm the exact names of the fields you are using in your aggregation pipeline.

Use `db.collection.findOne()` to view a sample document and identify field names and their types.

2

Check if the data type of a field matches what the aggregation operator expects. For example, a `$sum` operator typically expects numeric values.

If you are trying to sum a field that is stored as a string, you might need to use `$toInt` or `$toDouble` within your pipeline.

3

If you are using a `$lookup` stage, ensure that the `localField` and `foreignField` names are correct and that the fields exist in both the local and foreign collections.

db.collection.aggregate([
  { $lookup: {
      from: 'orders',
      localField: 'customerId',
      foreignField: '_id',
      as: 'customerOrders'
    } }
]);

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Related Errors

5 related errors

MongoDB Error 168: Invalid Pipeline Operator