Scan a DynamoDB table - Amazon DynamoDB

Scan a DynamoDB table

You can perform a scan on a DynamoDB table using the AWS Management Console, the AWS CLI, or an AWS SDK. For more information on scans, see Working with scans in DynamoDB.

Scan a DynamoDB table using an AWS SDK

The following code examples show how to scan a DynamoDB table using an AWS SDK.

.NET
AWS SDK for .NET
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

public static async Task<int> ScanTableAsync( AmazonDynamoDBClient client, string tableName, int startYear, int endYear) { var request = new ScanRequest { TableName = tableName, ExpressionAttributeNames = new Dictionary<string, string> { { "#yr", "year" }, }, ExpressionAttributeValues = new Dictionary<string, AttributeValue> { { ":y_a", new AttributeValue { N = startYear.ToString() } }, { ":y_z", new AttributeValue { N = endYear.ToString() } }, }, FilterExpression = "#yr between :y_a and :y_z", ProjectionExpression = "#yr, title, info.actors[0], info.directors, info.running_time_secs", Limit = 10 // Set a limit to demonstrate using the LastEvaluatedKey. }; // Keep track of how many movies were found. int foundCount = 0; var response = new ScanResponse(); do { response = await client.ScanAsync(request); foundCount += response.Items.Count; response.Items.ForEach(i => DisplayItem(i)); request.ExclusiveStartKey = response.LastEvaluatedKey; } while (response.LastEvaluatedKey.Count > 0); return foundCount; }
  • For API details, see Scan in AWS SDK for .NET API Reference.

Bash
AWS CLI with Bash script
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

############################################################################# # function dynamodb_scan # # This function scans a DynamoDB table. # # Parameters: # -n table_name -- The name of the table. # -f filter_expression -- The filter expression. # -a expression_attribute_names -- Path to JSON file containing the expression attribute names. # -v expression_attribute_values -- Path to JSON file containing the expression attribute values. # [-p projection_expression] -- Optional projection expression. # # Returns: # The items as json output. # And: # 0 - If successful. # 1 - If it fails. ########################################################################### function dynamodb_scan() { local table_name filter_expression expression_attribute_names expression_attribute_values projection_expression response local option OPTARG # Required to use getopts command in a function. # ###################################### # Function usage explanation ####################################### function usage() { echo "function dynamodb_scan" echo "Scan a DynamoDB table." echo " -n table_name -- The name of the table." echo " -f filter_expression -- The filter expression." echo " -a expression_attribute_names -- Path to JSON file containing the expression attribute names." echo " -v expression_attribute_values -- Path to JSON file containing the expression attribute values." echo " [-p projection_expression] -- Optional projection expression." echo "" } while getopts "n:f:a:v:p:h" option; do case "${option}" in n) table_name="${OPTARG}" ;; f) filter_expression="${OPTARG}" ;; a) expression_attribute_names="${OPTARG}" ;; v) expression_attribute_values="${OPTARG}" ;; p) projection_expression="${OPTARG}" ;; h) usage return 0 ;; \?) echo "Invalid parameter" usage return 1 ;; esac done export OPTIND=1 if [[ -z "$table_name" ]]; then errecho "ERROR: You must provide a table name with the -n parameter." usage return 1 fi if [[ -z "$filter_expression" ]]; then errecho "ERROR: You must provide a filter expression with the -f parameter." usage return 1 fi if [[ -z "$expression_attribute_names" ]]; then errecho "ERROR: You must provide expression attribute names with the -a parameter." usage return 1 fi if [[ -z "$expression_attribute_values" ]]; then errecho "ERROR: You must provide expression attribute values with the -v parameter." usage return 1 fi if [[ -z "$projection_expression" ]]; then response=$(aws dynamodb scan \ --table-name "$table_name" \ --filter-expression "$filter_expression" \ --expression-attribute-names file://"$expression_attribute_names" \ --expression-attribute-values file://"$expression_attribute_values") else response=$(aws dynamodb scan \ --table-name "$table_name" \ --filter-expression "$filter_expression" \ --expression-attribute-names file://"$expression_attribute_names" \ --expression-attribute-values file://"$expression_attribute_values" \ --projection-expression "$projection_expression") fi local error_code=${?} if [[ $error_code -ne 0 ]]; then aws_cli_error_log $error_code errecho "ERROR: AWS reports scan operation failed.$response" return 1 fi echo "$response" return 0 }

The utility functions used in this example.

############################################################################### # function errecho # # This function outputs everything sent to it to STDERR (standard error output). ############################################################################### function errecho() { printf "%s\n" "$*" 1>&2 } ############################################################################## # function aws_cli_error_log() # # This function is used to log the error messages from the AWS CLI. # # See https://docs.aws.amazon.com/cli/latest/topic/return-codes.html#cli-aws-help-return-codes. # # The function expects the following argument: # $1 - The error code returned by the AWS CLI. # # Returns: # 0: - Success. # ############################################################################## function aws_cli_error_log() { local err_code=$1 errecho "Error code : $err_code" if [ "$err_code" == 1 ]; then errecho " One or more S3 transfers failed." elif [ "$err_code" == 2 ]; then errecho " Command line failed to parse." elif [ "$err_code" == 130 ]; then errecho " Process received SIGINT." elif [ "$err_code" == 252 ]; then errecho " Command syntax invalid." elif [ "$err_code" == 253 ]; then errecho " The system environment or configuration was invalid." elif [ "$err_code" == 254 ]; then errecho " The service returned an error." elif [ "$err_code" == 255 ]; then errecho " 255 is a catch-all error." fi return 0 }
  • For API details, see Scan in AWS CLI Command Reference.

C++
SDK for C++
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

//! Scan an Amazon DynamoDB table. /*! \sa scanTable() \param tableName: Name for the DynamoDB table. \param projectionExpression: An optional projection expression, ignored if empty. \param clientConfiguration: AWS client configuration. \return bool: Function succeeded. */ bool AwsDoc::DynamoDB::scanTable(const Aws::String &tableName, const Aws::String &projectionExpression, const Aws::Client::ClientConfiguration &clientConfiguration) { Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration); Aws::DynamoDB::Model::ScanRequest request; request.SetTableName(tableName); if (!projectionExpression.empty()) request.SetProjectionExpression(projectionExpression); // Perform scan on table. const Aws::DynamoDB::Model::ScanOutcome &outcome = dynamoClient.Scan(request); if (outcome.IsSuccess()) { // Reference the retrieved items. const Aws::Vector<Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue>> &items = outcome.GetResult().GetItems(); if (!items.empty()) { std::cout << "Number of items retrieved from scan: " << items.size() << std::endl; // Iterate each item and print. for (const Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> &itemMap: items) { std::cout << "******************************************************" << std::endl; // Output each retrieved field and its value. for (const auto &itemEntry: itemMap) std::cout << itemEntry.first << ": " << itemEntry.second.GetS() << std::endl; } } else { std::cout << "No item found in table: " << tableName << std::endl; } } else { std::cerr << "Failed to Scan items: " << outcome.GetError().GetMessage() << std::endl; } return outcome.IsSuccess(); }
  • For API details, see Scan in AWS SDK for C++ API Reference.

CLI
AWS CLI

To scan a table

The following scan example scans the entire MusicCollection table, and then narrows the results to songs by the artist "No One You Know". For each item, only the album title and song title are returned.

aws dynamodb scan \ --table-name MusicCollection \ --filter-expression "Artist = :a" \ --projection-expression "#ST, #AT" \ --expression-attribute-names file://expression-attribute-names.json \ --expression-attribute-values file://expression-attribute-values.json

Contents of expression-attribute-names.json:

{ "#ST": "SongTitle", "#AT":"AlbumTitle" }

Contents of expression-attribute-values.json:

{ ":a": {"S": "No One You Know"} }

Output:

{ "Count": 2, "Items": [ { "SongTitle": { "S": "Call Me Today" }, "AlbumTitle": { "S": "Somewhat Famous" } }, { "SongTitle": { "S": "Scared of My Shadow" }, "AlbumTitle": { "S": "Blue Sky Blues" } } ], "ScannedCount": 3, "ConsumedCapacity": null }

For more information, see Working with Scans in DynamoDB in the Amazon DynamoDB Developer Guide.

  • For API details, see Scan in AWS CLI Command Reference.

Go
SDK for Go V2
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

// TableBasics encapsulates the Amazon DynamoDB service actions used in the examples. // It contains a DynamoDB service client that is used to act on the specified table. type TableBasics struct { DynamoDbClient *dynamodb.Client TableName string } // Scan gets all movies in the DynamoDB table that were released in a range of years // and projects them to return a reduced set of fields. // The function uses the `expression` package to build the filter and projection // expressions. func (basics TableBasics) Scan(startYear int, endYear int) ([]Movie, error) { var movies []Movie var err error var response *dynamodb.ScanOutput filtEx := expression.Name("year").Between(expression.Value(startYear), expression.Value(endYear)) projEx := expression.NamesList( expression.Name("year"), expression.Name("title"), expression.Name("info.rating")) expr, err := expression.NewBuilder().WithFilter(filtEx).WithProjection(projEx).Build() if err != nil { log.Printf("Couldn't build expressions for scan. Here's why: %v\n", err) } else { scanPaginator := dynamodb.NewScanPaginator(basics.DynamoDbClient, &dynamodb.ScanInput{ TableName: aws.String(basics.TableName), ExpressionAttributeNames: expr.Names(), ExpressionAttributeValues: expr.Values(), FilterExpression: expr.Filter(), ProjectionExpression: expr.Projection(), }) for scanPaginator.HasMorePages() { response, err = scanPaginator.NextPage(context.TODO()) if err != nil { log.Printf("Couldn't scan for movies released between %v and %v. Here's why: %v\n", startYear, endYear, err) break } else { var moviePage []Movie err = attributevalue.UnmarshalListOfMaps(response.Items, &moviePage) if err != nil { log.Printf("Couldn't unmarshal query response. Here's why: %v\n", err) break } else { movies = append(movies, moviePage...) } } } } return movies, err } // Movie encapsulates data about a movie. Title and Year are the composite primary key // of the movie in Amazon DynamoDB. Title is the sort key, Year is the partition key, // and Info is additional data. type Movie struct { Title string `dynamodbav:"title"` Year int `dynamodbav:"year"` Info map[string]interface{} `dynamodbav:"info"` } // GetKey returns the composite primary key of the movie in a format that can be // sent to DynamoDB. func (movie Movie) GetKey() map[string]types.AttributeValue { title, err := attributevalue.Marshal(movie.Title) if err != nil { panic(err) } year, err := attributevalue.Marshal(movie.Year) if err != nil { panic(err) } return map[string]types.AttributeValue{"title": title, "year": year} } // String returns the title, year, rating, and plot of a movie, formatted for the example. func (movie Movie) String() string { return fmt.Sprintf("%v\n\tReleased: %v\n\tRating: %v\n\tPlot: %v\n", movie.Title, movie.Year, movie.Info["rating"], movie.Info["plot"]) }
  • For API details, see Scan in AWS SDK for Go API Reference.

Java
SDK for Java 2.x
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

Scans an Amazon DynamoDB table using DynamoDbClient.

import software.amazon.awssdk.regions.Region; 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.ScanRequest; import software.amazon.awssdk.services.dynamodb.model.ScanResponse; import java.util.Map; import java.util.Set; /** * Before running this Java V2 code example, set up your development * environment, including your credentials. * * For more information, see the following documentation topic: * * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html * * To scan items from an Amazon DynamoDB table using the AWS SDK for Java V2, * its better practice to use the * Enhanced Client, See the EnhancedScanRecords example. */ public class DynamoDBScanItems { public static void main(String[] args) { final String usage = """ Usage: <tableName> Where: tableName - The Amazon DynamoDB table to get information from (for example, Music3). """; if (args.length != 1) { System.out.println(usage); System.exit(1); } String tableName = args[0]; Region region = Region.US_EAST_1; DynamoDbClient ddb = DynamoDbClient.builder() .region(region) .build(); scanItems(ddb, tableName); ddb.close(); } public static void scanItems(DynamoDbClient ddb, String tableName) { try { ScanRequest scanRequest = ScanRequest.builder() .tableName(tableName) .build(); ScanResponse response = ddb.scan(scanRequest); for (Map<String, AttributeValue> item : response.items()) { Set<String> keys = item.keySet(); for (String key : keys) { System.out.println("The key name is " + key + "\n"); System.out.println("The value is " + item.get(key).s()); } } } catch (DynamoDbException e) { e.printStackTrace(); System.exit(1); } } }
  • For API details, see Scan in AWS SDK for Java 2.x API Reference.

JavaScript
SDK for JavaScript (v3)
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

This example uses the document client to simplify working with items in DynamoDB. For API details see ScanCommand.

import { DynamoDBClient } from "@aws-sdk/client-dynamodb"; import { DynamoDBDocumentClient, ScanCommand } from "@aws-sdk/lib-dynamodb"; const client = new DynamoDBClient({}); const docClient = DynamoDBDocumentClient.from(client); export const main = async () => { const command = new ScanCommand({ ProjectionExpression: "#Name, Color, AvgLifeSpan", ExpressionAttributeNames: { "#Name": "Name" }, TableName: "Birds", }); const response = await docClient.send(command); for (const bird of response.Items) { console.log(`${bird.Name} - (${bird.Color}, ${bird.AvgLifeSpan})`); } return response; };
  • For API details, see Scan in AWS SDK for JavaScript API Reference.

SDK for JavaScript (v2)
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

// Load the AWS SDK for Node.js. var AWS = require("aws-sdk"); // Set the AWS Region. AWS.config.update({ region: "REGION" }); // Create DynamoDB service object. var ddb = new AWS.DynamoDB({ apiVersion: "2012-08-10" }); const params = { // Specify which items in the results are returned. FilterExpression: "Subtitle = :topic AND Season = :s AND Episode = :e", // Define the expression attribute value, which are substitutes for the values you want to compare. ExpressionAttributeValues: { ":topic": { S: "SubTitle2" }, ":s": { N: 1 }, ":e": { N: 2 }, }, // Set the projection expression, which are the attributes that you want. ProjectionExpression: "Season, Episode, Title, Subtitle", TableName: "EPISODES_TABLE", }; ddb.scan(params, function (err, data) { if (err) { console.log("Error", err); } else { console.log("Success", data); data.Items.forEach(function (element, index, array) { console.log( "printing", element.Title.S + " (" + element.Subtitle.S + ")" ); }); } });
Kotlin
SDK for Kotlin
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

suspend fun scanItems(tableNameVal: String) { val request = ScanRequest { tableName = tableNameVal } DynamoDbClient { region = "us-east-1" }.use { ddb -> val response = ddb.scan(request) response.items?.forEach { item -> item.keys.forEach { key -> println("The key name is $key\n") println("The value is ${item[key]}") } } } }
  • For API details, see Scan in AWS SDK for Kotlin API reference.

PHP
SDK for PHP
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

$yearsKey = [ 'Key' => [ 'year' => [ 'N' => [ 'minRange' => 1990, 'maxRange' => 1999, ], ], ], ]; $filter = "year between 1990 and 1999"; echo "\nHere's a list of all the movies released in the 90s:\n"; $result = $service->scan($tableName, $yearsKey, $filter); foreach ($result['Items'] as $movie) { $movie = $marshal->unmarshalItem($movie); echo $movie['title'] . "\n"; } public function scan(string $tableName, array $key, string $filters) { $query = [ 'ExpressionAttributeNames' => ['#year' => 'year'], 'ExpressionAttributeValues' => [ ":min" => ['N' => '1990'], ":max" => ['N' => '1999'], ], 'FilterExpression' => "#year between :min and :max", 'TableName' => $tableName, ]; return $this->dynamoDbClient->scan($query); }
  • For API details, see Scan in AWS SDK for PHP API Reference.

Python
SDK for Python (Boto3)
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

class Movies: """Encapsulates an Amazon DynamoDB table of movie data.""" def __init__(self, dyn_resource): """ :param dyn_resource: A Boto3 DynamoDB resource. """ self.dyn_resource = dyn_resource # The table variable is set during the scenario in the call to # 'exists' if the table exists. Otherwise, it is set by 'create_table'. self.table = None def scan_movies(self, year_range): """ Scans for movies that were released in a range of years. Uses a projection expression to return a subset of data for each movie. :param year_range: The range of years to retrieve. :return: The list of movies released in the specified years. """ movies = [] scan_kwargs = { "FilterExpression": Key("year").between( year_range["first"], year_range["second"] ), "ProjectionExpression": "#yr, title, info.rating", "ExpressionAttributeNames": {"#yr": "year"}, } try: done = False start_key = None while not done: if start_key: scan_kwargs["ExclusiveStartKey"] = start_key response = self.table.scan(**scan_kwargs) movies.extend(response.get("Items", [])) start_key = response.get("LastEvaluatedKey", None) done = start_key is None except ClientError as err: logger.error( "Couldn't scan for movies. Here's why: %s: %s", err.response["Error"]["Code"], err.response["Error"]["Message"], ) raise return movies
  • For API details, see Scan in AWS SDK for Python (Boto3) API Reference.

Ruby
SDK for Ruby
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

class DynamoDBBasics attr_reader :dynamo_resource attr_reader :table def initialize(table_name) client = Aws::DynamoDB::Client.new(region: "us-east-1") @dynamo_resource = Aws::DynamoDB::Resource.new(client: client) @table = @dynamo_resource.table(table_name) end # Scans for movies that were released in a range of years. # Uses a projection expression to return a subset of data for each movie. # # @param year_range [Hash] The range of years to retrieve. # @return [Array] The list of movies released in the specified years. def scan_items(year_range) movies = [] scan_hash = { filter_expression: "#yr between :start_yr and :end_yr", projection_expression: "#yr, title, info.rating", expression_attribute_names: {"#yr" => "year"}, expression_attribute_values: { ":start_yr" => year_range[:start], ":end_yr" => year_range[:end]} } done = false start_key = nil until done scan_hash[:exclusive_start_key] = start_key unless start_key.nil? response = @table.scan(scan_hash) movies.concat(response.items) unless response.items.empty? start_key = response.last_evaluated_key done = start_key.nil? end rescue Aws::DynamoDB::Errors::ServiceError => e puts("Couldn't scan for movies. Here's why:") puts("\t#{e.code}: #{e.message}") raise else movies end
  • For API details, see Scan in AWS SDK for Ruby API Reference.

Rust
SDK for Rust
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

pub async fn list_items(client: &Client, table: &str, page_size: Option<i32>) -> Result<(), Error> { let page_size = page_size.unwrap_or(10); let items: Result<Vec<_>, _> = client .scan() .table_name(table) .limit(page_size) .into_paginator() .items() .send() .collect() .await; println!("Items in table (up to {page_size}):"); for item in items? { println!(" {:?}", item); } Ok(()) }
  • For API details, see Scan in AWS SDK for Rust API reference.

SAP ABAP
SDK for SAP ABAP
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

TRY. " Scan movies for rating greater than or equal to the rating specified DATA(lt_attributelist) = VALUE /aws1/cl_dynattributevalue=>tt_attributevaluelist( ( NEW /aws1/cl_dynattributevalue( iv_n = |{ iv_rating }| ) ) ). DATA(lt_filter_conditions) = VALUE /aws1/cl_dyncondition=>tt_filterconditionmap( ( VALUE /aws1/cl_dyncondition=>ts_filterconditionmap_maprow( key = 'rating' value = NEW /aws1/cl_dyncondition( it_attributevaluelist = lt_attributelist iv_comparisonoperator = |GE| ) ) ) ). oo_scan_result = lo_dyn->scan( iv_tablename = iv_table_name it_scanfilter = lt_filter_conditions ). DATA(lt_items) = oo_scan_result->get_items( ). LOOP AT lt_items INTO DATA(lo_item). " You can loop over to get individual attributes. DATA(lo_title) = lo_item[ key = 'title' ]-value. DATA(lo_year) = lo_item[ key = 'year' ]-value. ENDLOOP. DATA(lv_count) = oo_scan_result->get_count( ). MESSAGE 'Found ' && lv_count && ' items' TYPE 'I'. CATCH /aws1/cx_dynresourcenotfoundex. MESSAGE 'The table or index does not exist' TYPE 'E'. ENDTRY.
  • For API details, see Scan in AWS SDK for SAP ABAP API reference.

Swift
SDK for Swift
Note

This is prerelease documentation for an SDK in preview release. It is subject to change.

Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

/// Return an array of `Movie` objects released in the specified range of /// years. /// /// - Parameters: /// - firstYear: The first year of movies to return. /// - lastYear: The last year of movies to return. /// - startKey: A starting point to resume processing; always use `nil`. /// /// - Returns: An array of `Movie` objects describing the matching movies. /// /// > Note: The `startKey` parameter is used by this function when /// recursively calling itself, and should always be `nil` when calling /// directly. /// func getMovies(firstYear: Int, lastYear: Int, startKey: [Swift.String:DynamoDBClientTypes.AttributeValue]? = nil) async throws -> [Movie] { var movieList: [Movie] = [] guard let client = self.ddbClient else { throw MoviesError.UninitializedClient } let input = ScanInput( consistentRead: true, exclusiveStartKey: startKey, expressionAttributeNames: [ "#y": "year" // `year` is a reserved word, so use `#y` instead. ], expressionAttributeValues: [ ":y1": .n(String(firstYear)), ":y2": .n(String(lastYear)) ], filterExpression: "#y BETWEEN :y1 AND :y2", tableName: self.tableName ) let output = try await client.scan(input: input) guard let items = output.items else { return movieList } // Build an array of `Movie` objects for the returned items. for item in items { let movie = try Movie(withItem: item) movieList.append(movie) } // Call this function recursively to continue collecting matching // movies, if necessary. if output.lastEvaluatedKey != nil { let movies = try await self.getMovies(firstYear: firstYear, lastYear: lastYear, startKey: output.lastEvaluatedKey) movieList += movies } return movieList }
  • For API details, see Scan in AWS SDK for Swift API reference.

For more DynamoDB examples, see Code examples for DynamoDB using AWS SDKs.