Amazon DynamoDB Query and Scan Iteration


This library provides utilities for automatically iterating over all DynamoDB
records returned by a query or scan operation using async iterables.
Each iterator and paginator included in this package automatically tracks
DynamoDB metadata and supports resuming iteration from any point within a full
query or scan.

Paginators

Paginators are asynchronous iterables that yield each page of results returned
by a DynamoDB query or scan operation. For sequential paginators, each
invocation of the next method corresponds to an invocation of the underlying
API operation until all no more pages are available.

$3

Retrieves all pages of a DynamoDB query in order.

#### Example usage

``typescript
import { QueryPaginator } from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const paginator = new QueryPaginator(
new DynamoDB({region: 'us-west-2'}),
{
TableName: 'my_table',
KeyConditionExpression: 'partitionKey = :value',
ExpressionAttributeValues: {
':value': {S: 'foo'}
},
ReturnConsumedCapacity: 'INDEXES'
}
);

for await (const page of paginator) {
// do something with page
}

// Inspect the total number of items yielded
console.log(paginator.count);

// Inspect the total number of items scanned by this operation
console.log(paginator.scannedCount);

// Inspect the capacity consumed by this operation
// This will only be available if ReturnConsumedCapacity was set on the input
console.log(paginator.consumedCapacity);
`

#### Suspending and resuming queries

You can suspend any running query from within the for loop by using the
break keyword. If there are still pages that have not been fetched, the
lastEvaluatedKey property of paginator will be defined. This can be provided
as the ExclusiveStartKey for another QueryPaginator instance:

`typescript
import { QueryPaginator } from '@aws/dynamodb-query-iterator';
import { QueryInput } from 'aws-sdk/clients/dynamodb';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const dynamoDb = new DynamoDB({region: 'us-west-2'});
const input: QueryInput = {
TableName: 'my_table',
KeyConditionExpression: 'partitionKey = :value',
ExpressionAttributeValues: {
':value': {S: 'foo'}
},
ReturnConsumedCapacity: 'INDEXES'
};

const paginator = new QueryPaginator(dynamoDb, input);

for await (const page of paginator) {
// do something with the first page of results
break
}

for await (const page of new QueryPaginator(dynamoDb, {
...input,
ExclusiveStartKey: paginator.lastEvaluatedKey
})) {
// do something with the remaining pages
}
`

Suspending and resuming the same paginator instance is not supported.

$3

Retrieves all pages of a DynamoDB scan in order.

#### Example usage

`typescript
import { ScanPaginator } from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const paginator = new ScanPaginator(
new DynamoDB({region: 'us-west-2'}),
{
TableName: 'my_table',
ReturnConsumedCapacity: 'INDEXES'
}
);

for await (const page of paginator) {
// do something with page
}

// Inspect the total number of items yielded
console.log(paginator.count);

// Inspect the total number of items scanned by this operation
console.log(paginator.scannedCount);

// Inspect the capacity consumed by this operation
// This will only be available if ReturnConsumedCapacity was set on the input
console.log(paginator.consumedCapacity);
`

#### Suspending and resuming scans

You can suspend any running scan from within the for loop by using the break
keyword. If there are still pages that have not been fetched, the
lastEvaluatedKey property of paginator will be defined. This can be provided
as the ExclusiveStartKey for another ScanPaginator instance:

`typescript
import { ScanPaginator } from '@aws/dynamodb-query-iterator';
import { ScanInput } from 'aws-sdk/clients/dynamodb';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const dynamoDb = new DynamoDB({region: 'us-west-2'});
const input: ScanInput = {
TableName: 'my_table',
ReturnConsumedCapacity: 'INDEXES'
};

const paginator = new ScanPaginator(dynamoDb, input);

for await (const page of paginator) {
// do something with the first page of results
break
}

for await (const page of new ScanPaginator(dynamoDb, {
...input,
ExclusiveStartKey: paginator.lastEvaluatedKey
})) {
// do something with the remaining pages
}
`

Suspending and resuming the same paginator instance is not supported.

$3

Retrieves all pages of a DynamoDB scan utilizing a configurable number of scan
segments that operate in parallel. When performing a parallel scan, you must
specify the total number of segments you wish to use, and neither an
ExclusiveStartKey nor a Segment identifier may be included with the input
provided.

#### Example usage

`typescript
import { ParallelScanPaginator } from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const paginator = new ParallelScanPaginator(
new DynamoDB({region: 'us-west-2'}),
{
TableName: 'my_table',
TotalSegments: 4,
ReturnConsumedCapacity: 'INDEXES'
}
);

for await (const page of paginator) {
// do something with page
}

// Inspect the total number of items yielded
console.log(paginator.count);

// Inspect the total number of items scanned by this operation
console.log(paginator.scannedCount);

// Inspect the capacity consumed by this operation
// This will only be available if ReturnConsumedCapacity was set on the input
console.log(paginator.consumedCapacity);
`

#### Suspending and resuming parallel scans

You can suspend any running scan from within the for loop by using the break
keyword. If there are still pages that have not been fetched, the scanState
property of interrupted paginator can be provided to the constructor of another
ParallelScanPaginator instance:

`typescript
import {
ParallelScanInput,
ParallelScanPaginator,
} from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const client = new DynamoDB({region: 'us-west-2'});
const input: ParallelScanInput = {
TableName: 'my_table',
TotalSegments: 4,
ReturnConsumedCapacity: 'INDEXES'
};

const paginator = new ParallelScanPaginator(client, input);

for await (const page of paginator) {
// do something with the first page of results
break
}

for await (const page of new ParallelScanPaginator(
client,
input,
paginator.scanState
)) {
// do something with the remaining pages
}
`

Suspending and resuming the same paginator instance is not supported.

Iterators

Iterators are asynchronous iterables that yield each of record returned by a
DynamoDB query or scan operation. Each invocation of the next method may
invoke the underlying API operation until all no more pages are available.

$3

Retrieves all records of a DynamoDB query in order.

#### Example usage

`typescript
import { QueryIterator } from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const iterator = new QueryIterator(
new DynamoDB({region: 'us-west-2'}),
{
TableName: 'my_table',
KeyConditionExpression: 'partitionKey = :value',
ExpressionAttributeValues: {
':value': {S: 'foo'}
},
ReturnConsumedCapacity: 'INDEXES'
},
['partitionKey']
);

for await (const record of iterator) {
// do something with record
}

// Inspect the total number of items yielded
console.log(iterator.count);

// Inspect the total number of items scanned by this operation
console.log(iterator.scannedCount);

// Inspect the capacity consumed by this operation
// This will only be available if ReturnConsumedCapacity was set on the input
console.log(iterator.consumedCapacity);
`

$3

Retrieves all records of a DynamoDB scan in order.

#### Example usage

`typescript
import { ScanIterator } from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const iterator = new ScanIterator(
new DynamoDB({region: 'us-west-2'}),
{
TableName: 'my_table',
ReturnConsumedCapacity: 'INDEXES'
},
['partitionKey', 'sortKey']
);

for await (const record of iterator) {
// do something with record
}

// Inspect the total number of items yielded
console.log(iterator.count);

// Inspect the total number of items scanned by this operation
console.log(iterator.scannedCount);

// Inspect the capacity consumed by this operation
// This will only be available if ReturnConsumedCapacity was set on the input
console.log(iterator.consumedCapacity);
`

$3

Retrieves all pages of a DynamoDB scan utilizing a configurable number of scan
segments that operate in parallel. When performing a parallel scan, you must
specify the total number of segments you wish to use, and neither an
ExclusiveStartKey nor a Segment identifier may be included with the input
provided.

#### Example usage

`typescript
import { ParallelScanIterator} from '@aws/dynamodb-query-iterator';
import DynamoDB = require('aws-sdk/clients/dynamodb');

const iterator = new ParallelScanIterator(
new DynamoDB({region: 'us-west-2'}),
{
TableName: 'my_table',
TotalSegments: 4,
ReturnConsumedCapacity: 'INDEXES'
},
['partitionKey']
);

for await (const record of iterator) {
// do something with record
}

// Inspect the total number of items yielded
console.log(iterator.count);

// Inspect the total number of items scanned by this operation
console.log(iterator.scannedCount);

// Inspect the capacity consumed by this operation
// This will only be available if ReturnConsumedCapacity was set on the input
console.log(iterator.consumedCapacity);
``