Use operações de contador atômico no DynamoDB com um SDK AWS

Demonstre as operações do contador atômico usando AWS SDK for Java 2.x.

import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
import software.amazon.awssdk.services.dynamodb.model.GetItemRequest;
import software.amazon.awssdk.services.dynamodb.model.GetItemResponse;
import software.amazon.awssdk.services.dynamodb.model.ReturnValue;
import software.amazon.awssdk.services.dynamodb.model.UpdateItemRequest;
import software.amazon.awssdk.services.dynamodb.model.UpdateItemResponse;

import java.util.HashMap;
import java.util.Map;

    /**
     * Increments a counter using the ADD operation.
     *
     * <p>This method demonstrates how to use the ADD operation to atomically
     * increment a counter attribute.
     *
     * @param dynamoDbClient The DynamoDB client
     * @param tableName The name of the DynamoDB table
     * @param key The key of the item to update
     * @param counterName The name of the counter attribute
     * @param incrementValue The value to increment by
     * @return The response from DynamoDB
     * @throws DynamoDbException if an error occurs during the operation
     */
    public static UpdateItemResponse incrementCounterWithAdd(
        DynamoDbClient dynamoDbClient,
        String tableName,
        Map<String, AttributeValue> key,
        String counterName,
        int incrementValue) {

        // Define the update parameters
        UpdateItemRequest request = UpdateItemRequest.builder()
            .tableName(tableName)
            .key(key)
            .updateExpression("ADD #counterName :increment")
            .expressionAttributeNames(Map.of("#counterName", counterName))
            .expressionAttributeValues(Map.of(
                ":increment",
                AttributeValue.builder().n(String.valueOf(incrementValue)).build()))
            .returnValues(ReturnValue.UPDATED_NEW)
            .build();

        // Perform the update operation
        return dynamoDbClient.updateItem(request);
    }

    /**
     * Increments a counter using the SET operation.
     *
     * <p>This method demonstrates how to use the SET operation with an expression
     * to increment a counter attribute.
     *
     * @param dynamoDbClient The DynamoDB client
     * @param tableName The name of the DynamoDB table
     * @param key The key of the item to update
     * @param counterName The name of the counter attribute
     * @param incrementValue The value to increment by
     * @return The response from DynamoDB
     * @throws DynamoDbException if an error occurs during the operation
     */
    public static UpdateItemResponse incrementCounterWithSet(
        DynamoDbClient dynamoDbClient,
        String tableName,
        Map<String, AttributeValue> key,
        String counterName,
        int incrementValue) {

        // Define the update parameters
        UpdateItemRequest request = UpdateItemRequest.builder()
            .tableName(tableName)
            .key(key)
            .updateExpression("SET #counterName = #counterName + :increment")
            .expressionAttributeNames(Map.of("#counterName", counterName))
            .expressionAttributeValues(Map.of(
                ":increment",
                AttributeValue.builder().n(String.valueOf(incrementValue)).build()))
            .returnValues(ReturnValue.UPDATED_NEW)
            .build();

        // Perform the update operation
        return dynamoDbClient.updateItem(request);
    }

    /**
     * Increments a counter safely, handling the case where the counter doesn't exist yet.
     *
     * <p>This method demonstrates how to use if_not_exists to safely increment a counter
     * that may not exist yet.
     *
     * @param dynamoDbClient The DynamoDB client
     * @param tableName The name of the DynamoDB table
     * @param key The key of the item to update
     * @param counterName The name of the counter attribute
     * @param incrementValue The value to increment by
     * @return The response from DynamoDB
     * @throws DynamoDbException if an error occurs during the operation
     */
    public static UpdateItemResponse incrementCounterSafely(
        DynamoDbClient dynamoDbClient,
        String tableName,
        Map<String, AttributeValue> key,
        String counterName,
        int incrementValue) {

        // Define the update parameters
        UpdateItemRequest request = UpdateItemRequest.builder()
            .tableName(tableName)
            .key(key)
            .updateExpression("SET #counterName = if_not_exists(#counterName, :zero) + :increment")
            .expressionAttributeNames(Map.of("#counterName", counterName))
            .expressionAttributeValues(Map.of(
                ":increment",
                    AttributeValue.builder().n(String.valueOf(incrementValue)).build(),
                ":zero", AttributeValue.builder().n("0").build()))
            .returnValues(ReturnValue.UPDATED_NEW)
            .build();

        // Perform the update operation
        return dynamoDbClient.updateItem(request);
    }

    /**
     * Decrements a counter safely, ensuring it doesn't go below zero.
     *
     * <p>This method demonstrates how to use a condition expression to safely
     * decrement a counter without going below zero.
     *
     * @param dynamoDbClient The DynamoDB client
     * @param tableName The name of the DynamoDB table
     * @param key The key of the item to update
     * @param counterName The name of the counter attribute
     * @param decrementValue The value to decrement by
     * @return The response from DynamoDB
     * @throws DynamoDbException if an error occurs during the operation or if the counter would go below zero
     */
    public static UpdateItemResponse decrementCounterSafely(
        DynamoDbClient dynamoDbClient,
        String tableName,
        Map<String, AttributeValue> key,
        String counterName,
        int decrementValue) {

        // Define the update parameters
        UpdateItemRequest request = UpdateItemRequest.builder()
            .tableName(tableName)
            .key(key)
            .updateExpression("SET #counterName = #counterName - :decrement")
            .conditionExpression("#counterName >= :decrement")
            .expressionAttributeNames(Map.of("#counterName", counterName))
            .expressionAttributeValues(Map.of(
                ":decrement",
                AttributeValue.builder().n(String.valueOf(decrementValue)).build()))
            .returnValues(ReturnValue.UPDATED_NEW)
            .build();

        // Perform the update operation
        return dynamoDbClient.updateItem(request);
    }

    /**
     * Compares the ADD and SET approaches for incrementing counters.
     *
     * <p>This method demonstrates the differences between using ADD and SET
     * for incrementing counters in DynamoDB.
     *
     * @param dynamoDbClient The DynamoDB client
     * @param tableName The name of the DynamoDB table
     * @param key The key of the item to update
     * @return Map containing the comparison results
     */
    public static Map<String, Object> compareAddVsSet(
        DynamoDbClient dynamoDbClient, String tableName, Map<String, AttributeValue> key) {

        Map<String, Object> results = new HashMap<>();

        try {
            // Reset counters to ensure a fair comparison
            UpdateItemRequest resetRequest = UpdateItemRequest.builder()
                .tableName(tableName)
                .key(key)
                .updateExpression("SET AddCounter = :zero, SetCounter = :zero")
                .expressionAttributeValues(
                    Map.of(":zero", AttributeValue.builder().n("0").build()))
                .build();

            dynamoDbClient.updateItem(resetRequest);

            // Increment with ADD
            long addStartTime = System.nanoTime();
            UpdateItemResponse addResponse = incrementCounterWithAdd(dynamoDbClient, tableName, key, "AddCounter", 1);
            long addEndTime = System.nanoTime();
            long addDuration = addEndTime - addStartTime;

            // Increment with SET
            long setStartTime = System.nanoTime();
            UpdateItemResponse setResponse = incrementCounterWithSet(dynamoDbClient, tableName, key, "SetCounter", 1);
            long setEndTime = System.nanoTime();
            long setDuration = setEndTime - setStartTime;

            // Record results
            results.put("addResponse", addResponse);
            results.put("setResponse", setResponse);
            results.put("addDuration", addDuration);
            results.put("setDuration", setDuration);
            results.put("success", true);

        } catch (DynamoDbException e) {
            results.put("success", false);
            results.put("error", e.getMessage());
        }

        return results;
    }

    /**
     * Gets the current value of a counter attribute.
     *
     * <p>Helper method to retrieve the current value of a counter attribute.
     *
     * @param dynamoDbClient The DynamoDB client
     * @param tableName The name of the DynamoDB table
     * @param key The key of the item to get
     * @param counterName The name of the counter attribute
     * @return The counter value or null if not found
     * @throws DynamoDbException if an error occurs during the operation
     */
    public static Integer getCounterValue(
        DynamoDbClient dynamoDbClient, String tableName, Map<String, AttributeValue> key, String counterName) {

        // Define the get parameters
        GetItemRequest request = GetItemRequest.builder()
            .tableName(tableName)
            .key(key)
            .projectionExpression(counterName)
            .build();

        // Perform the get operation
        GetItemResponse response = dynamoDbClient.getItem(request);

        // Return the counter value if it exists, otherwise null
        if (response.item() != null && response.item().containsKey(counterName)) {
            return Integer.parseInt(response.item().get(counterName).n());
        }

        return null;
    }

Exemplo de uso de operações de contador atômico com AWS SDK for Java 2.x.

    public static void exampleUsage(DynamoDbClient dynamoDbClient, String tableName) {
        // Example key
        Map<String, AttributeValue> key = new HashMap<>();
        key.put("ProductId", AttributeValue.builder().s("P12345").build());

        System.out.println("Demonstrating atomic counter operations in DynamoDB");

        try {
            // Example 1: Increment a counter using ADD
            System.out.println("\nExample 1: Incrementing a counter using ADD");
            UpdateItemResponse addResponse = incrementCounterWithAdd(dynamoDbClient, tableName, key, "ViewCount", 1);

            System.out.println("Updated counter: " + addResponse.attributes());

            // Example 2: Increment a counter using SET
            System.out.println("\nExample 2: Incrementing a counter using SET");
            UpdateItemResponse setResponse = incrementCounterWithSet(dynamoDbClient, tableName, key, "LikeCount", 1);

            System.out.println("Updated counter: " + setResponse.attributes());

            // Example 3: Increment a counter safely
            System.out.println("\nExample 3: Incrementing a counter safely");
            UpdateItemResponse safeResponse = incrementCounterSafely(dynamoDbClient, tableName, key, "ShareCount", 1);

            System.out.println("Updated counter: " + safeResponse.attributes());

            // Example 4: Decrement a counter safely
            System.out.println("\nExample 4: Decrementing a counter safely");
            try {
                UpdateItemResponse decrementResponse =
                    decrementCounterSafely(dynamoDbClient, tableName, key, "InventoryCount", 1);

                System.out.println("Updated counter: " + decrementResponse.attributes());
            } catch (DynamoDbException e) {
                if (e.getMessage().contains("ConditionalCheckFailed")) {
                    System.out.println("Cannot decrement counter below zero");
                } else {
                    throw e;
                }
            }

            // Example 5: Compare ADD vs SET
            System.out.println("\nExample 5: Comparing ADD vs SET");
            Map<String, Object> comparison = compareAddVsSet(dynamoDbClient, tableName, key);

            if ((boolean) comparison.get("success")) {
                System.out.println("ADD duration: " + comparison.get("addDuration") + " ns");
                System.out.println("SET duration: " + comparison.get("setDuration") + " ns");
                System.out.println("ADD response: " + comparison.get("addResponse"));
                System.out.println("SET response: " + comparison.get("setResponse"));
            } else {
                System.out.println("Comparison failed: " + comparison.get("error"));
            }

            // Explain atomic counter operations
            System.out.println("\nKey points about DynamoDB atomic counter operations:");
            System.out.println("1. Both ADD and SET can be used for atomic counters");
            System.out.println("2. ADD is more concise for simple increments");
            System.out.println("3. SET with an expression is more flexible for complex operations");
            System.out.println("4. Use if_not_exists to handle the case where the counter doesn't exist yet");
            System.out.println("5. Use condition expressions to prevent counters from going below zero");
            System.out.println("6. Atomic operations are guaranteed to be isolated from other writes");
            System.out.println("7. ADD can only be used with number and set data types");

        } catch (DynamoDbException e) {
            System.err.println("Error: " + e.getMessage());
            e.printStackTrace();
        }
    }

Demonstre as operações do contador atômico usando AWS SDK para JavaScript.

const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");
const { 
  DynamoDBDocumentClient, 
  UpdateCommand,
  GetCommand
} = require("@aws-sdk/lib-dynamodb");

/**
 * Increment a counter using the ADD operation.
 * 
 * This function demonstrates using the ADD operation for atomic increments.
 * The ADD operation is atomic and is the recommended way to increment counters.
 * 
 * @param {Object} config - AWS configuration object
 * @param {string} tableName - The name of the DynamoDB table
 * @param {Object} key - The key of the item to update
 * @param {string} counterName - The name of the counter attribute
 * @param {number} incrementValue - The value to increment by
 * @returns {Promise<Object>} - The response from DynamoDB
 */
async function incrementCounterWithAdd(
  config,
  tableName,
  key,
  counterName,
  incrementValue
) {
  // Initialize the DynamoDB client
  const client = new DynamoDBClient(config);
  const docClient = DynamoDBDocumentClient.from(client);
  
  // Define the update parameters using ADD
  const params = {
    TableName: tableName,
    Key: key,
    UpdateExpression: `ADD ${counterName} :increment`,
    ExpressionAttributeValues: {
      ":increment": incrementValue
    },
    ReturnValues: "UPDATED_NEW"
  };
  
  // Perform the update operation
  const response = await docClient.send(new UpdateCommand(params));
  
  return response;
}

/**
 * Increment a counter using the SET operation with an expression.
 * 
 * This function demonstrates using the SET operation with an expression for increments.
 * While this approach works, it's less idiomatic for simple increments than using ADD.
 * 
 * @param {Object} config - AWS configuration object
 * @param {string} tableName - The name of the DynamoDB table
 * @param {Object} key - The key of the item to update
 * @param {string} counterName - The name of the counter attribute
 * @param {number} incrementValue - The value to increment by
 * @returns {Promise<Object>} - The response from DynamoDB
 */
async function incrementCounterWithSet(
  config,
  tableName,
  key,
  counterName,
  incrementValue
) {
  // Initialize the DynamoDB client
  const client = new DynamoDBClient(config);
  const docClient = DynamoDBDocumentClient.from(client);
  
  // Define the update parameters using SET with an expression
  const params = {
    TableName: tableName,
    Key: key,
    UpdateExpression: `SET ${counterName} = ${counterName} + :increment`,
    ExpressionAttributeValues: {
      ":increment": incrementValue
    },
    ReturnValues: "UPDATED_NEW"
  };
  
  // Perform the update operation
  const response = await docClient.send(new UpdateCommand(params));
  
  return response;
}

/**
 * Increment a counter safely, handling the case where the counter might not exist.
 * 
 * This function demonstrates using the if_not_exists function with SET to safely
 * increment a counter that might not exist yet.
 * 
 * @param {Object} config - AWS configuration object
 * @param {string} tableName - The name of the DynamoDB table
 * @param {Object} key - The key of the item to update
 * @param {string} counterName - The name of the counter attribute
 * @param {number} incrementValue - The value to increment by
 * @param {number} defaultValue - The default value if the counter doesn't exist
 * @returns {Promise<Object>} - The response from DynamoDB
 */
async function incrementCounterSafely(
  config,
  tableName,
  key,
  counterName,
  incrementValue,
  defaultValue = 0
) {
  // Initialize the DynamoDB client
  const client = new DynamoDBClient(config);
  const docClient = DynamoDBDocumentClient.from(client);
  
  // Define the update parameters using SET with if_not_exists
  const params = {
    TableName: tableName,
    Key: key,
    UpdateExpression: `SET ${counterName} = if_not_exists(${counterName}, :default) + :increment`,
    ExpressionAttributeValues: {
      ":increment": incrementValue,
      ":default": defaultValue
    },
    ReturnValues: "UPDATED_NEW"
  };
  
  // Perform the update operation
  const response = await docClient.send(new UpdateCommand(params));
  
  return response;
}

/**
 * Increment a counter with optimistic locking to prevent race conditions.
 * 
 * This function demonstrates using a condition expression to implement optimistic
 * locking, which prevents race conditions when multiple processes try to update
 * the same counter.
 * 
 * @param {Object} config - AWS configuration object
 * @param {string} tableName - The name of the DynamoDB table
 * @param {Object} key - The key of the item to update
 * @param {string} counterName - The name of the counter attribute
 * @param {number} incrementValue - The value to increment by
 * @param {number} expectedValue - The expected current value of the counter
 * @returns {Promise<Object>} - The response from DynamoDB
 */
async function incrementCounterWithLocking(
  config,
  tableName,
  key,
  counterName,
  incrementValue,
  expectedValue
) {
  // Initialize the DynamoDB client
  const client = new DynamoDBClient(config);
  const docClient = DynamoDBDocumentClient.from(client);
  
  // Define the update parameters with a condition expression
  const params = {
    TableName: tableName,
    Key: key,
    UpdateExpression: `SET ${counterName} = ${counterName} + :increment`,
    ConditionExpression: `${counterName} = :expected`,
    ExpressionAttributeValues: {
      ":increment": incrementValue,
      ":expected": expectedValue
    },
    ReturnValues: "UPDATED_NEW"
  };
  
  try {
    // Perform the update operation
    const response = await docClient.send(new UpdateCommand(params));
    return {
      success: true,
      data: response
    };
  } catch (error) {
    // Check if the error is due to the condition check failing
    if (error.name === "ConditionalCheckFailedException") {
      return {
        success: false,
        error: "Optimistic locking failed: the counter value has changed"
      };
    }
    // Re-throw other errors
    throw error;
  }
}

/**
 * Get the current value of a counter.
 * 
 * Helper function to retrieve the current value of a counter attribute.
 * 
 * @param {Object} config - AWS configuration object
 * @param {string} tableName - The name of the DynamoDB table
 * @param {Object} key - The key of the item to get
 * @param {string} counterName - The name of the counter attribute
 * @returns {Promise<number|null>} - The current counter value or null if not found
 */
async function getCounterValue(
  config,
  tableName,
  key,
  counterName
) {
  // Initialize the DynamoDB client
  const client = new DynamoDBClient(config);
  const docClient = DynamoDBDocumentClient.from(client);
  
  // Define the get parameters
  const params = {
    TableName: tableName,
    Key: key
  };
  
  // Perform the get operation
  const response = await docClient.send(new GetCommand(params));
  
  // Return the counter value if it exists, otherwise null
  return response.Item && counterName in response.Item
    ? response.Item[counterName]
    : null;
}

Exemplo de uso de operações de contador atômico com AWS SDK para JavaScript.

/**
 * Example of how to use the atomic counter operations.
 */
async function exampleUsage() {
  // Example parameters
  const config = { region: "us-west-2" };
  const tableName = "Products";
  const key = { ProductId: "P12345" };
  const counterName = "ViewCount";
  const incrementValue = 1;
  
  console.log("Demonstrating different approaches to increment counters in DynamoDB");
  
  try {
    // Example 1: Using ADD operation (recommended for simple increments)
    console.log("\nExample 1: Incrementing counter with ADD operation");
    const response1 = await incrementCounterWithAdd(
      config,
      tableName,
      key,
      counterName,
      incrementValue
    );
    
    console.log(`Counter incremented to: ${response1.Attributes[counterName]}`);
    
    // Example 2: Using SET operation with an expression
    console.log("\nExample 2: Incrementing counter with SET operation");
    const response2 = await incrementCounterWithSet(
      config,
      tableName,
      key,
      counterName,
      incrementValue
    );
    
    console.log(`Counter incremented to: ${response2.Attributes[counterName]}`);
    
    // Example 3: Safely incrementing a counter that might not exist
    console.log("\nExample 3: Safely incrementing counter that might not exist");
    const newKey = { ProductId: "P67890" };
    const response3 = await incrementCounterSafely(
      config,
      tableName,
      newKey,
      counterName,
      incrementValue,
      0
    );
    
    console.log(`Counter initialized and incremented to: ${response3.Attributes[counterName]}`);
    
    // Example 4: Incrementing with optimistic locking
    console.log("\nExample 4: Incrementing with optimistic locking");
    
    // First, get the current counter value
    const currentValue = await getCounterValue(config, tableName, key, counterName);
    console.log(`Current counter value: ${currentValue}`);
    
    // Then, try to increment with optimistic locking
    const response4 = await incrementCounterWithLocking(
      config,
      tableName,
      key,
      counterName,
      incrementValue,
      currentValue
    );
    
    if (response4.success) {
      console.log(`Counter successfully incremented to: ${response4.data.Attributes[counterName]}`);
    } else {
      console.log(response4.error);
    }
    
    // Explain the differences between ADD and SET
    console.log("\nKey differences between ADD and SET for counter operations:");
    console.log("1. ADD is more concise and idiomatic for simple increments");
    console.log("2. SET with expressions is more flexible for complex operations");
    console.log("3. Both operations are atomic and safe for concurrent updates");
    console.log("4. SET with if_not_exists is required when the attribute might not exist");
    console.log("5. Optimistic locking can be added to either approach for additional safety");
    
  } catch (error) {
    console.error("Error:", error);
  }
}

Demonstre as operações do contador atômico usando AWS SDK para Python (Boto3).

import boto3
from botocore.exceptions import ClientError
from typing import Any, Dict, Union


def increment_counter_with_add(
    table_name: str, key: Dict[str, Any], counter_name: str, increment_value: int = 1
) -> Dict[str, Any]:
    """
    Increment a counter attribute using the ADD operation.

    This function demonstrates the atomic ADD operation, which is ideal for
    incrementing counters without the risk of race conditions.

    Args:
        table_name (str): The name of the DynamoDB table.
        key (Dict[str, Any]): The primary key of the item to update.
        counter_name (str): The name of the counter attribute.
        increment_value (int, optional): The value to increment by. Defaults to 1.

    Returns:
        Dict[str, Any]: The response from DynamoDB containing the updated attribute values.
    """
    # Initialize the DynamoDB resource
    dynamodb = boto3.resource("dynamodb")
    table = dynamodb.Table(table_name)

    # Use the ADD operation to atomically increment the counter
    response = table.update_item(
        Key=key,
        UpdateExpression="ADD #counter :increment",
        ExpressionAttributeNames={"#counter": counter_name},
        ExpressionAttributeValues={":increment": increment_value},
        ReturnValues="UPDATED_NEW",
    )

    return response


def increment_counter_with_set(
    table_name: str, key: Dict[str, Any], counter_name: str, increment_value: int = 1
) -> Dict[str, Any]:
    """
    Increment a counter attribute using the SET operation with an expression.

    This function demonstrates using SET with an expression to increment a counter.
    While this works, it's generally recommended to use ADD for simple increments.

    Args:
        table_name (str): The name of the DynamoDB table.
        key (Dict[str, Any]): The primary key of the item to update.
        counter_name (str): The name of the counter attribute.
        increment_value (int, optional): The value to increment by. Defaults to 1.

    Returns:
        Dict[str, Any]: The response from DynamoDB containing the updated attribute values.
    """
    # Initialize the DynamoDB resource
    dynamodb = boto3.resource("dynamodb")
    table = dynamodb.Table(table_name)

    # Use the SET operation with an expression to increment the counter
    response = table.update_item(
        Key=key,
        UpdateExpression="SET #counter = #counter + :increment",
        ExpressionAttributeNames={"#counter": counter_name},
        ExpressionAttributeValues={":increment": increment_value},
        ReturnValues="UPDATED_NEW",
    )

    return response


def increment_counter_safely(
    table_name: str,
    key: Dict[str, Any],
    counter_name: str,
    increment_value: int = 1,
    initial_value: int = 0,
) -> Dict[str, Any]:
    """
    Increment a counter attribute safely, handling the case where it might not exist.

    This function demonstrates a best practice for incrementing counters by using
    the if_not_exists function to handle the case where the counter doesn't exist yet.

    Args:
        table_name (str): The name of the DynamoDB table.
        key (Dict[str, Any]): The primary key of the item to update.
        counter_name (str): The name of the counter attribute.
        increment_value (int, optional): The value to increment by. Defaults to 1.
        initial_value (int, optional): The initial value if the counter doesn't exist. Defaults to 0.

    Returns:
        Dict[str, Any]: The response from DynamoDB containing the updated attribute values.
    """
    # Initialize the DynamoDB resource
    dynamodb = boto3.resource("dynamodb")
    table = dynamodb.Table(table_name)

    # Use SET with if_not_exists to safely increment the counter
    response = table.update_item(
        Key=key,
        UpdateExpression="SET #counter = if_not_exists(#counter, :initial) + :increment",
        ExpressionAttributeNames={"#counter": counter_name},
        ExpressionAttributeValues={":increment": increment_value, ":initial": initial_value},
        ReturnValues="UPDATED_NEW",
    )

    return response


def atomic_conditional_increment(
    table_name: str,
    key: Dict[str, Any],
    counter_name: str,
    condition_attribute: str,
    condition_value: Any,
    increment_value: int = 1,
) -> Union[Dict[str, Any], None]:
    """
    Atomically increment a counter only if a condition is met.

    This function demonstrates combining atomic counter operations with
    conditional expressions for more complex update scenarios.

    Args:
        table_name (str): The name of the DynamoDB table.
        key (Dict[str, Any]): The primary key of the item to update.
        counter_name (str): The name of the counter attribute.
        condition_attribute (str): The attribute to check in the condition.
        condition_value (Any): The value to compare against.
        increment_value (int, optional): The value to increment by. Defaults to 1.

    Returns:
        Optional[Dict[str, Any]]: The response from DynamoDB if successful, None if condition failed.
    """
    # Initialize the DynamoDB resource
    dynamodb = boto3.resource("dynamodb")
    table = dynamodb.Table(table_name)

    try:
        # Use ADD with a condition expression
        response = table.update_item(
            Key=key,
            UpdateExpression="ADD #counter :increment",
            ConditionExpression="#condition = :value",
            ExpressionAttributeNames={"#counter": counter_name, "#condition": condition_attribute},
            ExpressionAttributeValues={":increment": increment_value, ":value": condition_value},
            ReturnValues="UPDATED_NEW",
        )
        return response
    except ClientError as e:
        if e.response["Error"]["Code"] == "ConditionalCheckFailedException":
            # Condition was not met
            return None
        else:
            # Other error occurred
            raise

Exemplo de uso de operações de contador atômico com AWS SDK para Python (Boto3).

def example_usage():
    """Example of how to use the atomic counter operations functions."""
    # Example parameters
    table_name = "GameScores"
    key = {"UserId": "user123", "GameId": "game456"}
    counter_name = "Score"

    print("Example 1: Incrementing a counter with ADD operation")
    try:
        response = increment_counter_with_add(
            table_name=table_name, key=key, counter_name=counter_name, increment_value=10
        )
        print(
            f"Counter incremented successfully. New value: {response.get('Attributes', {}).get(counter_name)}"
        )
    except Exception as e:
        print(f"Error incrementing counter with ADD: {e}")

    print("\nExample 2: Incrementing a counter with SET operation")
    try:
        response = increment_counter_with_set(
            table_name=table_name, key=key, counter_name=counter_name, increment_value=5
        )
        print(
            f"Counter incremented successfully. New value: {response.get('Attributes', {}).get(counter_name)}"
        )
    except Exception as e:
        print(f"Error incrementing counter with SET: {e}")

    print("\nExample 3: Safely incrementing a counter that might not exist")
    try:
        new_key = {"UserId": "newuser789", "GameId": "game456"}
        response = increment_counter_safely(
            table_name=table_name,
            key=new_key,
            counter_name=counter_name,
            increment_value=15,
            initial_value=100,
        )
        print(
            f"Counter safely incremented. New value: {response.get('Attributes', {}).get(counter_name)}"
        )
    except Exception as e:
        print(f"Error safely incrementing counter: {e}")

    print("\nExample 4: Conditional counter increment")
    try:
        # Fix for mypy: Handle the case where response might be None
        result = atomic_conditional_increment(
            table_name=table_name,
            key=key,
            counter_name="Achievements",
            condition_attribute="Level",
            condition_value=5,
            increment_value=1,
        )

        if result is not None:
            print(
                f"Conditional increment succeeded. New value: {result.get('Attributes', {}).get('Achievements')}"
            )
        else:
            print("Conditional increment failed because condition was not met.")
        if response:
            print(
                f"Conditional increment succeeded. New value: {response.get('Attributes', {}).get('Achievements')}"
            )
        else:
            print("Conditional increment failed because condition was not met.")
    except Exception as e:
        print(f"Error with conditional increment: {e}")

    print("\nComparison of ADD vs SET for counter operations:")
    print("1. ADD is specifically designed for atomic numeric increments and set operations")
    print("2. SET with an expression can be used for more complex calculations")
    print("3. Both operations are atomic, preventing race conditions")
    print("4. ADD is more concise for simple increments")
    print("5. SET with if_not_exists() is recommended when the attribute might not exist")
    print("6. For counters, ADD is generally preferred for clarity and simplicity")