MongoDB $size OperatorWhat is the $size operator in MongoDB?MongoDB provides a variety of array expression operators, and the $size operator is one of those operators. The $size operator is used to find the total number of elements present in the given array, and it is also used in the aggregation pipeline stages. Syntax of the $size operator:Important points:
Examples:In the following examples, we are working with: >db.students.find().pretty() { "_id" : 1, "name" : "Jonny", "class" : "X", "rollNo" : 401, "age" : 18, "marks" : [ 55, 60, 70, 45, 95, 68 ], "extraMarks" : { "practical" : [ 21, 18, 25, 30 ], "attendance" : [ 5, 9 ] } "gender" : "Male", "bloodgroup" : "A+" } { "_id" : 2, "name" : "Carry", "class" : "IX", "rollNo" : 35, "age" : 17, "marks" : [ 85, 40, 90, 75, 85, 77 ], "gender" : "Male", "bloodgroup" : "B+" } { "_id" : 3, "name" : "Jin", "class" : "IX", "rollNo" : 49, "age" : 17, "marks" : [ 85, 70, 80, 95, 94, 81 ], "gender" : "Female", "bloodgroup" : "O+" } { "_id" : 4, "name" : "Thomas", "class" : "X", "rollNo" : 61, "age" : 18, "marks" : [ 91, 65, 71, 63, 98, 76 ], "extraMarks" : { "practical" : [ 26, 28, 25, 29 ], "attendance" : [ 8, 8 ] } "gender" : "Male", "bloodgroup" : "A+" } { "_id" : 5, "name" : "Mia", "class" : "IX", "rollNo" : 308, "age" : 17, "marks" : [ 97, 98, 95, 98 ], "gender" : "Female", "bloodgroup" : "B+" } { "_id" : 6, "name" : "Oats", "class" : "IX", "rollNo" : 75, "age" : 18, "marks" : [ 99, 98, 98, 95, 96 ], "gender" : "Male", "bloodgroup" : "A+" } Example 1: Using $size operator In this example, we are going to find the total size of the "marks" field using the $size operator. Output: { "name" : "Carry", "class" : "IX", "rollNo" : 35, "marks" : [ 85, 40, 90, 75, 85, 77 ], "gender" : "Male", "markssize" : 6 } { "name" : "Jin", "class" : "IX", "rollNo" : 49, "marks" : [ 85, 70, 80, 95, 94, 81 ], "gender" : "Female", "markssize" : 6 } { "name" : "Mia", "class" : "IX", "rollNo" : 308, "marks" : [ 97, 98, 95, 98 ], "gender" : "Female", "markssize" : 4 } { "name" : "Oats", "class" : "IX", "rollNo" : 75, "marks" : [ 99, 98, 98, 95, 96 ], "gender" : "Male", "markssize" : 5 } Example 2: Using $size operator in the embedded document In this example, we are going to find the total size of the extraMarks.practical field using the $size operator. Output: { "name" : "Jonny", "class" : "X", "rollNo" : 401, "marks" : [ 55, 60, 70, 45, 95, 68 ], "extraMarks" : { "practical" : [ 21, 18, 25, 30 ], "attendance" : [ 5, 9 ] } "gender" : "Male", "result" : 4 } { "name" : "Thomas", "class" : "X", "rollNo" : 61, "marks" : [ 91, 65, 71, 63, 98, 76 ], "extraMarks" : { "practical" : [ 26, 28, 25, 29 ], "attendance" : [ 8, 8 ] } "gender" : "Male", "result" : 4 } Next TopicMongoDB $rename operator |