MongoDB : $match

1. MongoDB $match Aggregation

Definition

The $match stage in MongoDB's aggregation pipeline filters documents based on specified conditions. It acts like a query operator to filter documents before passing them to the next stage. This is typically used as an early stage in the pipeline to reduce the number of documents that need processing.

Algorithm 1: Basic $match Usage :-

Step 1: Select your collection

Step 2: Define match criteria

Step 3: Apply comparison operators if needed

Step 4: Structure the match query

Step 5: Execute the pipeline

Example 1: Simple Match Filtering

// Filter students with high math scores

db.students.aggregate([

  {

    $match: {

      mathScore: { $gte: 90 },

      grade: "A"

    }

  }

])

Algorithm 2: Advanced $match Operations :-

Step 1: Identify complex filter conditions

Step 2: Combine multiple conditions

Step 3: Use logical operators

Step 4: Apply regex or array operators if needed

Step 5: Test the filter results

Example 2: Complex Match Conditions

// Complex matching with multiple conditions

db.orders.aggregate([

  {

    $match: {

      $and: [

        { status: "active" },

        { orderDate: { $gte: ISODate("2023-01-01") } },

        { totalAmount: { $gt: 1000 } },

        { "customer.type": "premium" },

        { tags: { $in: ["electronics", "gadgets"] } }

      ]

    }

  }

])