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merged 4 commits into from
Aug 18, 2025
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refactor(parser): Improve DynamoDB models with examples and descriptions #7146

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4bee949
#7123 Tech debt: Improve documentation of Event model fields in Dynam…
sreejaaryahi18 Aug 10, 2025
4e0e097
refactor(parser): address PR review feedback for DynamoDB models
sreejaaryahi18 Aug 15, 2025
938d4dc
Merge branch 'develop' into docs/dynamodb-model-examples
leandrodamascena Aug 18, 2025
436761d
Addressing changes
leandrodamascena Aug 18, 2025
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118 changes: 88 additions & 30 deletions aws_lambda_powertools/utilities/parser/models/dynamodb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,53 +2,111 @@
from datetime import datetime
from typing import Any, Dict, List, Literal, Optional, Type, Union

from pydantic import BaseModel, field_validator
from pydantic import BaseModel, Field, field_validator

from aws_lambda_powertools.shared.dynamodb_deserializer import TypeDeserializer

_DESERIALIZER = TypeDeserializer()


class DynamoDBStreamChangedRecordModel(BaseModel):
ApproximateCreationDateTime: Optional[datetime] = None
Keys: Dict[str, Any]
NewImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = None
OldImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = None
SequenceNumber: str
SizeBytes: int
StreamViewType: Literal["NEW_AND_OLD_IMAGES", "KEYS_ONLY", "NEW_IMAGE", "OLD_IMAGE"]

# context on why it's commented: https://github.com/aws-powertools/powertools-lambda-python/pull/118
# since both images are optional, they can both be None. However, at least one must
# exist in a legal model of NEW_AND_OLD_IMAGES type
# @root_validator
# def check_one_image_exists(cls, values): # noqa: ERA001
# new_img, old_img = values.get("NewImage"), values.get("OldImage") # noqa: ERA001
# stream_type = values.get("StreamViewType") # noqa: ERA001
# if stream_type == "NEW_AND_OLD_IMAGES" and not new_img and not old_img: # noqa: ERA001
# raise TypeError("DynamoDB streams model failed validation, missing both new & old stream images") # noqa: ERA001,E501
# return values # noqa: ERA001
ApproximateCreationDateTime: Optional[datetime] = Field( # AWS sends this as Unix epoch float
default=None,
description="The approximate date and time when the stream record was created (Unix epoch time).",
examples=[1693997155.0],
)
Keys: Dict[str, Any] = Field(description="Primary key attributes for the item.", examples=[{"Id": {"N": "101"}}])
NewImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = Field(
default=None,
description="The item after modifications, in DynamoDB attribute-value format.",
examples=[{"Message": {"S": "New item!"}, "Id": {"N": "101"}}],
)
OldImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = Field(
default=None,
description="The item before modifications, in DynamoDB attribute-value format.",
examples=[{"Message": {"S": "Old item!"}, "Id": {"N": "100"}}],
)
SequenceNumber: str = Field(description="A unique identifier for the stream record.", examples=["222"])
SizeBytes: int = Field(description="The size of the stream record, in bytes.", examples=[26])
StreamViewType: Literal["NEW_AND_OLD_IMAGES", "KEYS_ONLY", "NEW_IMAGE", "OLD_IMAGE"] = Field(
description="The type of data included in the stream record.",
examples=["NEW_AND_OLD_IMAGES"],
)

@field_validator("Keys", "NewImage", "OldImage", mode="before")
def deserialize_field(cls, value):
return {k: _DESERIALIZER.deserialize(v) for k, v in value.items()}


class UserIdentity(BaseModel):
type: Literal["Service"] # noqa: VNE003, A003
principalId: Literal["dynamodb.amazonaws.com"]
type: Literal["Service"] = Field(
description="The type of identity that made the request, which is always 'Service' for DynamoDB streams.",
examples=["Service"],
)
principalId: Literal["dynamodb.amazonaws.com"] = Field(
description="The unique identifier for the principal that made the request.",
examples=["dynamodb.amazonaws.com"],
)


class DynamoDBStreamRecordModel(BaseModel):
eventID: str
eventName: Literal["INSERT", "MODIFY", "REMOVE"]
eventVersion: float
eventSource: Literal["aws:dynamodb"]
awsRegion: str
eventSourceARN: str
dynamodb: DynamoDBStreamChangedRecordModel
userIdentity: Optional[UserIdentity] = None
eventID: str = Field(description="A unique identifier for the event.", examples=["1"])
eventName: Literal["INSERT", "MODIFY", "REMOVE"] = Field(
description="The type of operation that was performed on the item.",
examples=["INSERT"],
)
eventVersion: float = Field(description="The version of the stream record format.", examples=["1.0"])
eventSource: Literal["aws:dynamodb"] = Field(
description="The source of the event, which is always 'aws:dynamodb' for DynamoDB streams.",
examples=["aws:dynamodb"],
)
awsRegion: str = Field(description="The AWS region where the stream record was generated.", examples=["us-west-2"])
eventSourceARN: str = Field(
description="The Amazon Resource Name (ARN) of the DynamoDB stream.",
examples=["arn:aws:dynamodb:us-west-2:123456789012:table/ExampleTable/stream/2021-01-01T00:00:00.000"],
)
dynamodb: DynamoDBStreamChangedRecordModel = Field(
description="Contains the details of the DynamoDB stream record.",
examples=[
{
"ApproximateCreationDateTime": 1693997155.0,
"Keys": {"Id": {"N": "101"}},
"NewImage": {"Message": {"S": "New item!"}, "Id": {"N": "101"}},
"OldImage": {"Message": {"S": "Old item!"}, "Id": {"N": "100"}},
"SequenceNumber": "222",
"SizeBytes": 26,
"StreamViewType": "NEW_AND_OLD_IMAGES",
},
],
)
userIdentity: Optional[UserIdentity] = Field(
default=None,
description="Information about the identity that made the request.",
examples=[{"type": "Service", "principalId": "dynamodb.amazonaws.com"}],
)


class DynamoDBStreamModel(BaseModel):
Records: List[DynamoDBStreamRecordModel]
Records: List[DynamoDBStreamRecordModel] = Field(
description="A list of records that contain the details of the DynamoDB stream events.",
examples=[
{
"eventID": "1",
"eventName": "INSERT",
"eventVersion": "1.0",
"eventSource": "aws:dynamodb",
"awsRegion": "us-west-2",
"eventSourceARN": "arn:aws:dynamodb:us-west-2:123456789012:table/ExampleTable/stream/2021-01-01T00:00:00.000", # noqa E501
"dynamodb": {
"ApproximateCreationDateTime": 1693997155.0,
"Keys": {"Id": {"N": "101"}},
"NewImage": {"Message": {"S": "New item!"}, "Id": {"N": "101"}},
"OldImage": {"Message": {"S": "Old item!"}, "Id": {"N": "100"}},
"SequenceNumber": "222",
"SizeBytes": 26,
"StreamViewType": "NEW_AND_OLD_IMAGES",
},
"userIdentity": {"type": "Service", "principalId": "dynamodb.amazonaws.com"},
},
],
)
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