api_op_GetItem.go

// Code generated by smithy-go-codegen DO NOT EDIT.

package dynamodb

import (
	"context"
	"fmt"
	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
	internalEndpointDiscovery "github.com/aws/aws-sdk-go-v2/service/internal/endpoint-discovery"
	"github.com/aws/smithy-go/middleware"
	smithyhttp "github.com/aws/smithy-go/transport/http"
)

// The GetItem operation returns a set of attributes for the item with the given
// primary key. If there is no matching item, GetItem does not return any data and
// there will be no Item element in the response.
//
// GetItem provides an eventually consistent read by default. If your application
// requires a strongly consistent read, set ConsistentRead to true . Although a
// strongly consistent read might take more time than an eventually consistent
// read, it always returns the last updated value.
func (c *Client) GetItem(ctx context.Context, params *GetItemInput, optFns ...func(*Options)) (*GetItemOutput, error) {
	if params == nil {
		params = &GetItemInput{}
	}

	result, metadata, err := c.invokeOperation(ctx, "GetItem", params, optFns, c.addOperationGetItemMiddlewares)
	if err != nil {
		return nil, err
	}

	out := result.(*GetItemOutput)
	out.ResultMetadata = metadata
	return out, nil
}

// Represents the input of a GetItem operation.
type GetItemInput struct {

	// A map of attribute names to AttributeValue objects, representing the primary
	// key of the item to retrieve.
	//
	// For the primary key, you must provide all of the attributes. For example, with
	// a simple primary key, you only need to provide a value for the partition key.
	// For a composite primary key, you must provide values for both the partition key
	// and the sort key.
	//
	// This member is required.
	Key map[string]types.AttributeValue

	// The name of the table containing the requested item. You can also provide the
	// Amazon Resource Name (ARN) of the table in this parameter.
	//
	// This member is required.
	TableName *string

	// This is a legacy parameter. Use ProjectionExpression instead. For more
	// information, see [AttributesToGet]in the Amazon DynamoDB Developer Guide.
	//
	// [AttributesToGet]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html
	AttributesToGet []string

	// Determines the read consistency model: If set to true , then the operation uses
	// strongly consistent reads; otherwise, the operation uses eventually consistent
	// reads.
	ConsistentRead *bool

	// 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.
	//
	// [Reserved Words]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html
	// [Specifying Item Attributes]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html
	ExpressionAttributeNames map[string]string

	// A string that identifies one or more attributes to retrieve from the table.
	// 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 are returned. If any
	// of the requested attributes are not found, they do not appear in the result.
	//
	// For more information, see [Specifying Item Attributes] in the Amazon DynamoDB Developer Guide.
	//
	// [Specifying Item Attributes]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html
	ProjectionExpression *string

	// 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.
	ReturnConsumedCapacity types.ReturnConsumedCapacity

	noSmithyDocumentSerde
}

// Represents the output of a GetItem operation.
type GetItemOutput struct {

	// The capacity units consumed by the GetItem 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 [Provisioned Throughput]in the Amazon DynamoDB Developer Guide.
	//
	// [Provisioned Throughput]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ProvisionedThroughput.html#ItemSizeCalculations.Reads
	ConsumedCapacity *types.ConsumedCapacity

	// A map of attribute names to AttributeValue objects, as specified by
	// ProjectionExpression .
	Item map[string]types.AttributeValue

	// Metadata pertaining to the operation's result.
	ResultMetadata middleware.Metadata

	noSmithyDocumentSerde
}

func (c *Client) addOperationGetItemMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsAwsjson10_serializeOpGetItem{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsAwsjson10_deserializeOpGetItem{}, middleware.After)
	if err != nil {
		return err
	}
	if err := addProtocolFinalizerMiddlewares(stack, options, "GetItem"); err != nil {
		return fmt.Errorf("add protocol finalizers: %v", err)
	}

	if err = addlegacyEndpointContextSetter(stack, options); err != nil {
		return err
	}
	if err = addSetLoggerMiddleware(stack, options); err != nil {
		return err
	}
	if err = addClientRequestID(stack); err != nil {
		return err
	}
	if err = addComputeContentLength(stack); err != nil {
		return err
	}
	if err = addResolveEndpointMiddleware(stack, options); err != nil {
		return err
	}
	if err = addComputePayloadSHA256(stack); err != nil {
		return err
	}
	if err = addRetry(stack, options); err != nil {
		return err
	}
	if err = addRawResponseToMetadata(stack); err != nil {
		return err
	}
	if err = addRecordResponseTiming(stack); err != nil {
		return err
	}
	if err = addClientUserAgent(stack, options); err != nil {
		return err
	}
	if err = smithyhttp.AddErrorCloseResponseBodyMiddleware(stack); err != nil {
		return err
	}
	if err = smithyhttp.AddCloseResponseBodyMiddleware(stack); err != nil {
		return err
	}
	if err = addOpGetItemDiscoverEndpointMiddleware(stack, options, c); err != nil {
		return err
	}
	if err = addSetLegacyContextSigningOptionsMiddleware(stack); err != nil {
		return err
	}
	if err = addOpGetItemValidationMiddleware(stack); err != nil {
		return err
	}
	if err = stack.Initialize.Add(newServiceMetadataMiddleware_opGetItem(options.Region), middleware.Before); err != nil {
		return err
	}
	if err = addRecursionDetection(stack); err != nil {
		return err
	}
	if err = addRequestIDRetrieverMiddleware(stack); err != nil {
		return err
	}
	if err = addResponseErrorMiddleware(stack); err != nil {
		return err
	}
	if err = addValidateResponseChecksum(stack, options); err != nil {
		return err
	}
	if err = addAcceptEncodingGzip(stack, options); err != nil {
		return err
	}
	if err = addRequestResponseLogging(stack, options); err != nil {
		return err
	}
	if err = addDisableHTTPSMiddleware(stack, options); err != nil {
		return err
	}
	return nil
}

func addOpGetItemDiscoverEndpointMiddleware(stack *middleware.Stack, o Options, c *Client) error {
	return stack.Finalize.Insert(&internalEndpointDiscovery.DiscoverEndpoint{
		Options: []func(*internalEndpointDiscovery.DiscoverEndpointOptions){
			func(opt *internalEndpointDiscovery.DiscoverEndpointOptions) {
				opt.DisableHTTPS = o.EndpointOptions.DisableHTTPS
				opt.Logger = o.Logger
			},
		},
		DiscoverOperation:            c.fetchOpGetItemDiscoverEndpoint,
		EndpointDiscoveryEnableState: o.EndpointDiscovery.EnableEndpointDiscovery,
		EndpointDiscoveryRequired:    false,
		Region:                       o.Region,
	}, "ResolveEndpointV2", middleware.After)
}

func (c *Client) fetchOpGetItemDiscoverEndpoint(ctx context.Context, region string, optFns ...func(*internalEndpointDiscovery.DiscoverEndpointOptions)) (internalEndpointDiscovery.WeightedAddress, error) {
	input := getOperationInput(ctx)
	in, ok := input.(*GetItemInput)
	if !ok {
		return internalEndpointDiscovery.WeightedAddress{}, fmt.Errorf("unknown input type %T", input)
	}
	_ = in

	identifierMap := make(map[string]string, 0)
	identifierMap["sdk#Region"] = region

	key := fmt.Sprintf("DynamoDB.%v", identifierMap)

	if v, ok := c.endpointCache.Get(key); ok {
		return v, nil
	}

	discoveryOperationInput := &DescribeEndpointsInput{}

	opt := internalEndpointDiscovery.DiscoverEndpointOptions{}
	for _, fn := range optFns {
		fn(&opt)
	}

	go c.handleEndpointDiscoveryFromService(ctx, discoveryOperationInput, region, key, opt)
	return internalEndpointDiscovery.WeightedAddress{}, nil
}

func newServiceMetadataMiddleware_opGetItem(region string) *awsmiddleware.RegisterServiceMetadata {
	return &awsmiddleware.RegisterServiceMetadata{
		Region:        region,
		ServiceID:     ServiceID,
		OperationName: "GetItem",
	}
}