@aws-sdk/client-dynamodb/commands/ScanCommand.ts

AWS SDK for JavaScript Dynamodb Client for Node.js, Browser and React Native

import { DynamoDBClientResolvedConfig, ServiceInputTypes, ServiceOutputTypes } from "../DynamoDBClient";
import { ScanInput, ScanOutput } from "../models/models_0";
import { deserializeAws_json1_0ScanCommand, serializeAws_json1_0ScanCommand } from "../protocols/Aws_json1_0";
import { getSerdePlugin } from "@aws-sdk/middleware-serde";
import { HttpRequest as __HttpRequest, HttpResponse as __HttpResponse } from "@aws-sdk/protocol-http";
import { Command as $Command } from "@aws-sdk/smithy-client";
import {
  FinalizeHandlerArguments,
  Handler,
  HandlerExecutionContext,
  MiddlewareStack,
  HttpHandlerOptions as __HttpHandlerOptions,
  MetadataBearer as __MetadataBearer,
  SerdeContext as __SerdeContext,
} from "@aws-sdk/types";

export type ScanCommandInput = ScanInput;
export type ScanCommandOutput = ScanOutput & __MetadataBearer;

/**
 * <p>The <code>Scan</code> operation returns one or more items and item attributes by accessing every
 *       item in a table or a secondary index. To have DynamoDB return fewer items, you can provide a <code>FilterExpression</code> operation.</p>
 *          <p>If the total number of scanned items exceeds the maximum dataset size limit of 1 MB, the
 *             scan stops and results are returned to the user as a <code>LastEvaluatedKey</code> value
 *             to continue the scan in a subsequent operation. The results also include the number of
 *             items exceeding the limit. A scan can result in no table data meeting the filter
 *             criteria. </p>
 *          <p>A single <code>Scan</code> operation reads up to the maximum number of items set (if
 *             using the <code>Limit</code> parameter) or a maximum of 1 MB of data and then apply any
 *             filtering to the results using <code>FilterExpression</code>. If
 *                 <code>LastEvaluatedKey</code> is present in the response, you need to paginate the
 *             result set. For more information, see <a href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Scan.html#Scan.Pagination">Paginating the
 *                 Results</a> in the <i>Amazon DynamoDB Developer Guide</i>. </p>
 *          <p>
 *             <code>Scan</code> operations proceed sequentially; however, for faster performance on
 *             a large table or secondary index, applications can request a parallel <code>Scan</code>
 *             operation by providing the <code>Segment</code> and <code>TotalSegments</code>
 *             parameters. For more information, see <a href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Scan.html#Scan.ParallelScan">Parallel
 *                 Scan</a> in the <i>Amazon DynamoDB Developer Guide</i>.</p>
 *          <p>
 *             <code>Scan</code> uses eventually consistent reads when accessing the data in a
 *             table; therefore, the result set might not include the changes to data in the table
 *             immediately before the operation began. If you need a consistent copy of the data, as of
 *             the time that the <code>Scan</code> begins, you can set the <code>ConsistentRead</code>
 *             parameter to <code>true</code>.</p>
 */
export class ScanCommand extends $Command<ScanCommandInput, ScanCommandOutput, DynamoDBClientResolvedConfig> {
  private resolved = false;
  // Start section: command_properties
  // End section: command_properties

  constructor(readonly input: ScanCommandInput) {
    // Start section: command_constructor
    super();
    // End section: command_constructor
  }

  /**
   * @internal
   */
  resolveMiddleware(
    clientStack: MiddlewareStack<ServiceInputTypes, ServiceOutputTypes>,
    configuration: DynamoDBClientResolvedConfig,
    options?: __HttpHandlerOptions
  ): Handler<ScanCommandInput, ScanCommandOutput> {
    if (!this.resolved) {
      this.middlewareStack.use(getSerdePlugin(configuration, this.serialize, this.deserialize));
      this.resolved = true;
    }

    const stack = clientStack.concat(this.middlewareStack);

    const { logger } = configuration;
    const clientName = "DynamoDBClient";
    const commandName = "ScanCommand";
    const handlerExecutionContext: HandlerExecutionContext = {
      logger,
      clientName,
      commandName,
      inputFilterSensitiveLog: ScanInput.filterSensitiveLog,
      outputFilterSensitiveLog: ScanOutput.filterSensitiveLog,
    };
    const { requestHandler } = configuration;
    return stack.resolve(
      (request: FinalizeHandlerArguments<any>) =>
        requestHandler.handle(request.request as __HttpRequest, options || {}),
      handlerExecutionContext
    );
  }

  private serialize(input: ScanCommandInput, context: __SerdeContext): Promise<__HttpRequest> {
    return serializeAws_json1_0ScanCommand(input, context);
  }

  private deserialize(output: __HttpResponse, context: __SerdeContext): Promise<ScanCommandOutput> {
    return deserializeAws_json1_0ScanCommand(output, context);
  }

  // Start section: command_body_extra
  // End section: command_body_extra
}