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ScanCommand

The Scan 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 FilterExpression operation.

If the total size of scanned items exceeds the maximum dataset size limit of 1 MB, the scan completes and results are returned to the user. The LastEvaluatedKey value is also returned and the requestor can use the LastEvaluatedKey to continue the scan in a subsequent operation. Each scan response also includes number of items that were scanned (ScannedCount) as part of the request. If using a FilterExpression, a scan result can result in no items meeting the criteria and the Count will result in zero. If you did not use a FilterExpression in the scan request, then Count is the same as ScannedCount.

Count and ScannedCount only return the count of items specific to a single scan request and, unless the table is less than 1MB, do not represent the total number of items in the table.

A single Scan operation first reads up to the maximum number of items set (if using the Limit parameter) or a maximum of 1 MB of data and then applies any filtering to the results if a FilterExpression is provided. If LastEvaluatedKey is present in the response, pagination is required to complete the full table scan. For more information, see Paginating the Results in the Amazon DynamoDB Developer Guide.

Scan operations proceed sequentially; however, for faster performance on a large table or secondary index, applications can request a parallel Scan operation by providing the Segment and TotalSegments parameters. For more information, see Parallel Scan in the Amazon DynamoDB Developer Guide.

By default, a Scan uses eventually consistent reads when accessing the items in a table. Therefore, the results from an eventually consistent Scan may not include the latest item changes at the time the scan iterates through each item in the table. If you require a strongly consistent read of each item as the scan iterates through the items in the table, you can set the ConsistentRead parameter to true. Strong consistency only relates to the consistency of the read at the item level.

DynamoDB does not provide snapshot isolation for a scan operation when the ConsistentRead parameter is set to true. Thus, a DynamoDB scan operation does not guarantee that all reads in a scan see a consistent snapshot of the table when the scan operation was requested.

Example Syntax

Use a bare-bones client and the command you need to make an API call.

import { DynamoDBClient, ScanCommand } from "@aws-sdk/client-dynamodb"; // ES Modules import
// const { DynamoDBClient, ScanCommand } = require("@aws-sdk/client-dynamodb"); // CommonJS import
const client = new DynamoDBClient(config);
const input = { // ScanInput
  TableName: "STRING_VALUE", // required
  IndexName: "STRING_VALUE",
  AttributesToGet: [ // AttributeNameList
    "STRING_VALUE",
  ],
  Limit: Number("int"),
  Select: "ALL_ATTRIBUTES" || "ALL_PROJECTED_ATTRIBUTES" || "SPECIFIC_ATTRIBUTES" || "COUNT",
  ScanFilter: { // FilterConditionMap
    "<keys>": { // Condition
      AttributeValueList: [ // AttributeValueList
        { // AttributeValue Union: only one key present
          S: "STRING_VALUE",
          N: "STRING_VALUE",
          B: new Uint8Array(), // e.g. Buffer.from("") or new TextEncoder().encode("")
          SS: [ // StringSetAttributeValue
            "STRING_VALUE",
          ],
          NS: [ // NumberSetAttributeValue
            "STRING_VALUE",
          ],
          BS: [ // BinarySetAttributeValue
            new Uint8Array(), // e.g. Buffer.from("") or new TextEncoder().encode("")
          ],
          M: { // MapAttributeValue
            "<keys>": {//  Union: only one key present
              S: "STRING_VALUE",
              N: "STRING_VALUE",
              B: new Uint8Array(), // e.g. Buffer.from("") or new TextEncoder().encode("")
              SS: [
                "STRING_VALUE",
              ],
              NS: [
                "STRING_VALUE",
              ],
              BS: [
                new Uint8Array(), // e.g. Buffer.from("") or new TextEncoder().encode("")
              ],
              M: {
                "<keys>": "<AttributeValue>",
              },
              L: [ // ListAttributeValue
                "<AttributeValue>",
              ],
              NULL: true || false,
              BOOL: true || false,
            },
          },
          L: [
            "<AttributeValue>",
          ],
          NULL: true || false,
          BOOL: true || false,
        },
      ],
      ComparisonOperator: "EQ" || "NE" || "IN" || "LE" || "LT" || "GE" || "GT" || "BETWEEN" || "NOT_NULL" || "NULL" || "CONTAINS" || "NOT_CONTAINS" || "BEGINS_WITH", // required
    },
  },
  ConditionalOperator: "AND" || "OR",
  ExclusiveStartKey: { // Key
    "<keys>": "<AttributeValue>",
  },
  ReturnConsumedCapacity: "INDEXES" || "TOTAL" || "NONE",
  TotalSegments: Number("int"),
  Segment: Number("int"),
  ProjectionExpression: "STRING_VALUE",
  FilterExpression: "STRING_VALUE",
  ExpressionAttributeNames: { // ExpressionAttributeNameMap
    "<keys>": "STRING_VALUE",
  },
  ExpressionAttributeValues: { // ExpressionAttributeValueMap
    "<keys>": "<AttributeValue>",
  },
  ConsistentRead: true || false,
};
const command = new ScanCommand(input);
const response = await client.send(command);
// { // ScanOutput
//   Items: [ // ItemList
//     { // AttributeMap
//       "<keys>": { // AttributeValue Union: only one key present
//         S: "STRING_VALUE",
//         N: "STRING_VALUE",
//         B: new Uint8Array(),
//         SS: [ // StringSetAttributeValue
//           "STRING_VALUE",
//         ],
//         NS: [ // NumberSetAttributeValue
//           "STRING_VALUE",
//         ],
//         BS: [ // BinarySetAttributeValue
//           new Uint8Array(),
//         ],
//         M: { // MapAttributeValue
//           "<keys>": {//  Union: only one key present
//             S: "STRING_VALUE",
//             N: "STRING_VALUE",
//             B: new Uint8Array(),
//             SS: [
//               "STRING_VALUE",
//             ],
//             NS: [
//               "STRING_VALUE",
//             ],
//             BS: [
//               new Uint8Array(),
//             ],
//             M: {
//               "<keys>": "<AttributeValue>",
//             },
//             L: [ // ListAttributeValue
//               "<AttributeValue>",
//             ],
//             NULL: true || false,
//             BOOL: true || false,
//           },
//         },
//         L: [
//           "<AttributeValue>",
//         ],
//         NULL: true || false,
//         BOOL: true || false,
//       },
//     },
//   ],
//   Count: Number("int"),
//   ScannedCount: Number("int"),
//   LastEvaluatedKey: { // Key
//     "<keys>": "<AttributeValue>",
//   },
//   ConsumedCapacity: { // ConsumedCapacity
//     TableName: "STRING_VALUE",
//     CapacityUnits: Number("double"),
//     ReadCapacityUnits: Number("double"),
//     WriteCapacityUnits: Number("double"),
//     Table: { // Capacity
//       ReadCapacityUnits: Number("double"),
//       WriteCapacityUnits: Number("double"),
//       CapacityUnits: Number("double"),
//     },
//     LocalSecondaryIndexes: { // SecondaryIndexesCapacityMap
//       "<keys>": {
//         ReadCapacityUnits: Number("double"),
//         WriteCapacityUnits: Number("double"),
//         CapacityUnits: Number("double"),
//       },
//     },
//     GlobalSecondaryIndexes: {
//       "<keys>": {
//         ReadCapacityUnits: Number("double"),
//         WriteCapacityUnits: Number("double"),
//         CapacityUnits: Number("double"),
//       },
//     },
//   },
// };

Example Usage

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ScanCommand Input

See ScanCommandInput for more details

Parameter	Type	Description
`TableName` Required	`string \| undefined`	The name of the table containing the requested items or if you provide `IndexName`, the name of the table to which that index belongs. You can also provide the Amazon Resource Name (ARN) of the table in this parameter.
`AttributesToGet`	`string[] \| undefined`	This is a legacy parameter. Use `ProjectionExpression` instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide.
`ConditionalOperator`	`ConditionalOperator \| undefined`	This is a legacy parameter. Use `FilterExpression` instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.
`ConsistentRead`	`boolean \| undefined`	A Boolean value that determines the read consistency model during the scan: If `ConsistentRead` is `false`, then the data returned from `Scan` might not contain the results from other recently completed write operations (`PutItem`, `UpdateItem`, or `DeleteItem`). If `ConsistentRead` is `true`, then all of the write operations that completed before the `Scan` began are guaranteed to be contained in the `Scan` response. The default setting for `ConsistentRead` is `false`. The `ConsistentRead` parameter is not supported on global secondary indexes. If you scan a global secondary index with `ConsistentRead` set to true, you will receive a `ValidationException`.
`ExclusiveStartKey`	`Record<string, AttributeValue> \| undefined`	The primary key of the first item that this operation will evaluate. Use the value that was returned for `LastEvaluatedKey` in the previous operation. The data type for `ExclusiveStartKey` must be String, Number or Binary. No set data types are allowed. In a parallel scan, a `Scan` request that includes `ExclusiveStartKey` must specify the same segment whose previous `Scan` returned the corresponding value of `LastEvaluatedKey`.
`ExpressionAttributeNames`	`Record<string, string> \| undefined`	One or more substitution tokens for attribute names in an expression. The following are some use cases for using `ExpressionAttributeNames`: To access an attribute whose name conflicts with a DynamoDB reserved word. To create a placeholder for repeating occurrences of an attribute name in an expression. To prevent special characters in an attribute name from being misinterpreted in an expression. Use the # character in an expression to dereference an attribute name. For example, consider the following attribute name: `Percentile` The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see Reserved Words in the Amazon DynamoDB Developer Guide). To work around this, you could specify the following for `ExpressionAttributeNames`: `{"#P":"Percentile"}` You could then use this substitution in an expression, as in this example: `#P = :val` Tokens that begin with the : character are expression attribute values, which are placeholders for the actual value at runtime. For more information on expression attribute names, see Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
`ExpressionAttributeValues`	`Record<string, AttributeValue> \| undefined`	One or more values that can be substituted in an expression. Use the : (colon) character in an expression to dereference an attribute value. For example, suppose that you wanted to check whether the value of the `ProductStatus` attribute was one of the following: `Available \| Backordered \| Discontinued` You would first need to specify `ExpressionAttributeValues` as follows: `{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"}, ":disc":{"S":"Discontinued"} }` You could then use these values in an expression, such as this: `ProductStatus IN (:avail, :back, :disc)` For more information on expression attribute values, see Condition Expressions in the Amazon DynamoDB Developer Guide.
`FilterExpression`	`string \| undefined`	A string that contains conditions that DynamoDB applies after the `Scan` operation, but before the data is returned to you. Items that do not satisfy the `FilterExpression` criteria are not returned. A `FilterExpression` is applied after the items have already been read; the process of filtering does not consume any additional read capacity units. For more information, see Filter Expressions in the Amazon DynamoDB Developer Guide.
`IndexName`	`string \| undefined`	The name of a secondary index to scan. This index can be any local secondary index or global secondary index. Note that if you use the `IndexName` parameter, you must also provide `TableName`.
`Limit`	`number \| undefined`	The maximum number of items to evaluate (not necessarily the number of matching items). If DynamoDB processes the number of items up to the limit while processing the results, it stops the operation and returns the matching values up to that point, and a key in `LastEvaluatedKey` to apply in a subsequent operation, so that you can pick up where you left off. Also, if the processed dataset size exceeds 1 MB before DynamoDB reaches this limit, it stops the operation and returns the matching values up to the limit, and a key in `LastEvaluatedKey` to apply in a subsequent operation to continue the operation. For more information, see Working with Queries in the Amazon DynamoDB Developer Guide.
`ProjectionExpression`	`string \| undefined`	A string that identifies one or more attributes to retrieve from the specified table or index. These attributes can include scalars, sets, or elements of a JSON document. The attributes in the expression must be separated by commas. If no attribute names are specified, then all attributes will be returned. If any of the requested attributes are not found, they will not appear in the result. For more information, see Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
`ReturnConsumedCapacity`	`ReturnConsumedCapacity \| undefined`	Determines the level of detail about either provisioned or on-demand throughput consumption that is returned in the response: `INDEXES` - The response includes the aggregate `ConsumedCapacity` for the operation, together with `ConsumedCapacity` for each table and secondary index that was accessed. Note that some operations, such as `GetItem` and `BatchGetItem`, do not access any indexes at all. In these cases, specifying `INDEXES` will only return `ConsumedCapacity` information for table(s). `TOTAL` - The response includes only the aggregate `ConsumedCapacity` for the operation. `NONE` - No `ConsumedCapacity` details are included in the response.
`ScanFilter`	`Record<string, Condition> \| undefined`	This is a legacy parameter. Use `FilterExpression` instead. For more information, see ScanFilter in the Amazon DynamoDB Developer Guide.
`Segment`	`number \| undefined`	For a parallel `Scan` request, `Segment` identifies an individual segment to be scanned by an application worker. Segment IDs are zero-based, so the first segment is always 0. For example, if you want to use four application threads to scan a table or an index, then the first thread specifies a `Segment` value of 0, the second thread specifies 1, and so on. The value of `LastEvaluatedKey` returned from a parallel `Scan` request must be used as `ExclusiveStartKey` with the same segment ID in a subsequent `Scan` operation. The value for `Segment` must be greater than or equal to 0, and less than the value provided for `TotalSegments`. If you provide `Segment`, you must also provide `TotalSegments`.
`Select`	`Select \| undefined`	The attributes to be returned in the result. You can retrieve all item attributes, specific item attributes, the count of matching items, or in the case of an index, some or all of the attributes projected into the index. `ALL_ATTRIBUTES` - Returns all of the item attributes from the specified table or index. If you query a local secondary index, then for each matching item in the index, DynamoDB fetches the entire item from the parent table. If the index is configured to project all item attributes, then all of the data can be obtained from the local secondary index, and no fetching is required. `ALL_PROJECTED_ATTRIBUTES` - Allowed only when querying an index. Retrieves all attributes that have been projected into the index. If the index is configured to project all attributes, this return value is equivalent to specifying `ALL_ATTRIBUTES`. `COUNT` - Returns the number of matching items, rather than the matching items themselves. Note that this uses the same quantity of read capacity units as getting the items, and is subject to the same item size calculations. `SPECIFIC_ATTRIBUTES` - Returns only the attributes listed in `ProjectionExpression`. This return value is equivalent to specifying `ProjectionExpression` without specifying any value for `Select`. If you query or scan a local secondary index and request only attributes that are projected into that index, the operation reads only the index and not the table. If any of the requested attributes are not projected into the local secondary index, DynamoDB fetches each of these attributes from the parent table. This extra fetching incurs additional throughput cost and latency. If you query or scan a global secondary index, you can only request attributes that are projected into the index. Global secondary index queries cannot fetch attributes from the parent table. If neither `Select` nor `ProjectionExpression` are specified, DynamoDB defaults to `ALL_ATTRIBUTES` when accessing a table, and `ALL_PROJECTED_ATTRIBUTES` when accessing an index. You cannot use both `Select` and `ProjectionExpression` together in a single request, unless the value for `Select` is `SPECIFIC_ATTRIBUTES`. (This usage is equivalent to specifying `ProjectionExpression` without any value for `Select`.) If you use the `ProjectionExpression` parameter, then the value for `Select` can only be `SPECIFIC_ATTRIBUTES`. Any other value for `Select` will return an error.
`TotalSegments`	`number \| undefined`	For a parallel `Scan` request, `TotalSegments` represents the total number of segments into which the `Scan` operation will be divided. The value of `TotalSegments` corresponds to the number of application workers that will perform the parallel scan. For example, if you want to use four application threads to scan a table or an index, specify a `TotalSegments` value of 4. The value for `TotalSegments` must be greater than or equal to 1, and less than or equal to 1000000. If you specify a `TotalSegments` value of 1, the `Scan` operation will be sequential rather than parallel. If you specify `TotalSegments`, you must also specify `Segment`.

ScanCommand Output

See ScanCommandOutput for details

Parameter	Type	Description
`$metadata` Required	`ResponseMetadata`	Metadata pertaining to this request.
`ConsumedCapacity`	`ConsumedCapacity \| undefined`	The capacity units consumed by the `Scan` operation. The data returned includes the total provisioned throughput consumed, along with statistics for the table and any indexes involved in the operation. `ConsumedCapacity` is only returned if the `ReturnConsumedCapacity` parameter was specified. For more information, see Capacity unit consumption for read operations in the Amazon DynamoDB Developer Guide.
`Count`	`number \| undefined`	The number of items in the response. If you set `ScanFilter` in the request, then `Count` is the number of items returned after the filter was applied, and `ScannedCount` is the number of matching items before the filter was applied. If you did not use a filter in the request, then `Count` is the same as `ScannedCount`.
`Items`	`Record<string, AttributeValue>[] \| undefined`	An array of item attributes that match the scan criteria. Each element in this array consists of an attribute name and the value for that attribute.
`LastEvaluatedKey`	`Record<string, AttributeValue> \| undefined`	The primary key of the item where the operation stopped, inclusive of the previous result set. Use this value to start a new operation, excluding this value in the new request. If `LastEvaluatedKey` is empty, then the "last page" of results has been processed and there is no more data to be retrieved. If `LastEvaluatedKey` is not empty, it does not necessarily mean that there is more data in the result set. The only way to know when you have reached the end of the result set is when `LastEvaluatedKey` is empty.
`ScannedCount`	`number \| undefined`	The number of items evaluated, before any `ScanFilter` is applied. A high `ScannedCount` value with few, or no, `Count` results indicates an inefficient `Scan` operation. For more information, see Count and ScannedCount in the Amazon DynamoDB Developer Guide. If you did not use a filter in the request, then `ScannedCount` is the same as `Count`.

Throws

Name	Fault	Details
InternalServerError	server	An error occurred on the server side.
InvalidEndpointException	client
ProvisionedThroughputExceededException	client	Your request rate is too high. The Amazon Web Services SDKs for DynamoDB automatically retry requests that receive this exception. Your request is eventually successful, unless your retry queue is too large to finish. Reduce the frequency of requests and use exponential backoff. For more information, go to Error Retries and Exponential Backoff in the Amazon DynamoDB Developer Guide.
RequestLimitExceeded	client	Throughput exceeds the current throughput quota for your account. Please contact Amazon Web ServicesSupport to request a quota increase.
ResourceNotFoundException	client	The operation tried to access a nonexistent table or index. The resource might not be specified correctly, or its status might not be `ACTIVE`.
DynamoDBServiceException		Base exception class for all service exceptions from DynamoDB service.

Getting Started

References