API Compatibility

This section describes APIs supported by GeminiDB DynamoDB-Compatible API.

Usage Notes

You can add, delete, and modify tables of GeminiDB DynamoDB-Compatible instances only through DynamoDB APIs. Tables can only be read on the console.
Tables created through non-DynamoDB APIs cannot be used on GeminiDB DynamoDB-Compatible instances.
The current version does not support traffic statistics, traffic control, or transaction functions (TransactWriteItems and TransactGetItems).
The current version does not support the following on-demand backup APIs: CreateBackup, DescribeBackup, DeleteBackup, ListBackups, and RestoreTableFromBackup.
Hash or partition keys determine where items are stored in an internal storage device of a GeminiDB DynamoDB-Compatible instance. Amazon DynamoDB uses a dedicated hash function, while GeminiDB DynamoDB-Compatible API uses the Murmur3 algorithm. As a result, the sequence of data returned by a scan operation is different.
The table or index name cannot contain periods (.).
Due to different encoding methods, the size of each row of data in a table on a GeminiDB DynamoDB-Compatible instance is not strictly limited to 400 KB.
All DDL APIs are synchronous APIs.

Supported Expressions

ConditionExpression of GeminiDB DynamoDB-Compatible API supports the following function syntax:

function ::=
    attribute_exists (path)
    | attribute_not_exists (path)
    | attribute_type (path, type)
    | begins_with (path, substr)
    | contains (path, operand)
operand in contains(path,operand) can only be an attribute value (that is, the value placeholder).

UpdateExpression of GeminiDB DynamoDB-Compatible API supports the following syntax:

update-expression ::=
     [ SET action [, action] ... ]
     [ REMOVE action [, action] ...]
     [ ADD action [, action] ... ]
     [ DELETE action [, action] ...]

 set-action ::=
     path =value

 value ::=
     operand
     | operand '+' operand
     | operand '-' operand

 operand ::=
     path | function

 function ::=
     if_not_exists (path, value)
     | list_append (list1, list2)

 remove-action ::=
     path

 add-action ::=
     path value

 delete-action ::=
     path value
In SET path = operand, operand cannot be set to path.
In SET path = operand1 '+'|'-' operand2, operand1 must be set to path, and operand2 must be an attribute value.
In SET path = if_not_exists (path, value), values of the two path parameters must be the same and must be expression attribute values.
All values can only be placeholders, for example, ':placeholder'.

Compatible APIs

**Table 1** API list
API
CreateTable
UpdateTable
DescribeTable
ListTables
DeleteTable
PutItem
UpdateItem
GetItem
DeleteItem
BatchWriteItem
BatchGetItem
Query
Scan
UpdateTimeToLive
DescribeTimeToLive

**Table 2** CreateTable
API	Parameter		Mandatory	Supported	Remarks
CreateTable	Request parameter	AttributeDefinitions	Yes	Yes	-
		KeySchema	Yes	Yes	-
		TableName	Yes	Yes	Can contain 3 to 48 characters. The regular expression is ([\w-]+).
		BillingMode	No	No	Billing parameter, which is not supported
		GlobalSecondaryIndexes	No	Yes	-
		LocalSecondaryIndexes	No	Yes	-
		ProvisionedThroughput	Yes	Yes	-
		SSESpecification	No	No	Not supported in the current version (planning).
		StreamSpecification	No	Yes	-
		Tags	No	No	Not supported in the current version (planning).
	Response parameter	TableDescription	-	Yes	-

**Table 3** UpdateTable
API	Parameter		Mandatory	Supported	Remarks
UpdateTable	Request parameter	AttributeDefinitions	No	Yes	-
		BillingMode	No	No	Billing parameter, which is not supported
		GlobalSecondaryIndexesUpdates	Yes	Yes	CREATE and DELETE are supported, but UPDATE is not.
		ProvisionedThroughput	No	No	Billing parameter, which is not supported
		ReplicaUpdates	No	No	Default strong consistency
		SSESpecification	No	No	Not supported in the current version (planning).
		StreamSpecification	No	Yes	-
		TableName	Yes	Yes	-
	Response parameter	TableDescription	-	Yes	-

**Table 4** DescribeTable
API	Parameter		Mandatory	Supported	Remarks
DescribeTable	Request parameter	TableName	Yes	Yes	-
DescribeTable	Response parameter	Table	-	Yes	itemCount is not supported.

**Table 5** ListTables
API	Parameter		Mandatory	Supported	Remarks
ListTables	Request parameter	ExclusiveStartTableName	No	Yes	-
	Request parameter	Limit	No	Yes	-
	Response parameter	LastEvaluatedTableName	-	Yes	-
	Response parameter	TableNames	-	Yes	-

**Table 6** DeleteTable
API	Parameter		Mandatory	Supported	Remarks
DeleteTable	Request parameter	TableName	Yes	Yes	-
DeleteTable	Response parameter	TableDescription	-	Yes	-

**Table 7** PutItem
API	Parameter		Mandatory	Supported	Remarks
PutItem	Request parameter	Item	Yes	Yes	-
		TableName	Yes	Yes	-
		ConditionalOperator	No	No	Deprecated parameter. For details, see ConditionExpression.
		ConditionExpression	No	Yes	-
		Expected	No	No	Deprecated parameter. For details, see ConditionExpression.
		ExpressionAttributeNames	No	Yes	-
		ExpressionAttributeValues	No	Yes	-
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
		ReturnItemCollectionMetrics	No	No	Statistics parameter, which is not supported
		ReturnValues	No	Yes	-
	Response parameter	Attributes	-	Yes	-
		ConsumedCapacity	-	No	Billing parameter, which is not supported
		ItemCollectionMetrics	-	No	Statistics parameter, which is not supported

**Table 8** UpdateItem
API	Parameter		Mandatory	Supported	Remarks
UpdateItem	Request parameter	Key	Yes	Yes	-
		TableName	Yes	Yes	-
		AttributeUpdates	No	No	Deprecated parameter. For details, see UpdateExpression.
		ConditionalOperator	No	No	Deprecated parameter. For details, see UpdateExpression.
		ConditionExpression	No	Yes	-
		Expected	No	No	Deprecated parameter. For details, see UpdateExpression.
		ExpressionAttributeNames	No	Yes	-
		ExpressionAttributeValues	No	Yes	-
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
		ReturnItemCollectionMetrics	No	No	Statistics parameter, which is not supported
		ReturnValues	No	Yes	-
		UpdateExpression	No	Yes	-
	Response parameter	Attributes	-	Yes	-
		ConsumedCapacity	-	No	Billing parameter, which is not supported
		ItemCollectionMetrics	-	No	Statistics parameter, which is not supported

**Table 9** GetItem
API	Parameter		Mandatory	Supported	Remarks
GetItem	Request parameter	Key	Yes	Yes	-
		TableName	Yes	Yes	-
		AttributesToGet	No	No	Deprecated parameter. For details, see ProjectionExpression.
		ConsistentRead	No	No	Default strong consistency
		ExpressionAttributeNames	No	Yes	-
		ProjectionExpression	No	Yes	-
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
	Response parameter	ConsumedCapacity	-	No	Billing parameter, which is not supported
	Response parameter	Item	-	Yes	-

**Table 10** DeleteItem
API	Parameter		Mandatory	Supported	Remarks
DeleteItem	Request parameter	Key	Yes	Yes	-
		TableName	Yes	Yes	-
		ConditionalOperator	No	No	Deprecated parameter. For details, see ConditionExpression.
		ConditionExpression	No	Yes	-
		Expected	No	No	Deprecated parameter. For details, see ConditionExpression.
		ExpressionAttributeNames	No	Yes	-
		ExpressionAttributeValues	No	Yes	-
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
		ReturnItemCollectionMetrics	No	No	Statistics parameter, which is not supported
		ReturnValues	No	Yes	-
	Response parameter	Attributes	-	Yes	-
		ConsumedCapacity	-	No	Billing parameter, which is not supported
		ItemCollectionMetrics	-	No	Statistics parameter, which is not supported

**Table 11** BatchWriteItem
API	Parameter		Mandatory	Supported	Remarks
BatchWriteItem	Request parameter	RequestItems	Yes	Yes	-
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
		ReturnItemCollectionMetrics	No	No	Statistics parameter, which is not supported
	Response parameter	ConsumedCapacity	-	No	Billing parameter, which is not supported
		ItemCollectionMetrics	-	No	Statistics parameter, which is not supported
		UnprocessedItems	-	Yes	-

**Table 12** BatchGetItem
API	Parameter		Mandatory	Supported	Remarks
BatchGetItem	Request parameter	RequestItems	Yes	Yes	None
	Request parameter	ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
	Response parameter	ConsumedCapacity	-	No	Statistics parameter, which is not supported
		Responses	-	Yes	-
		UnprocessedKeys	-	Yes	-

**Table 13** Query
API	Parameter		Mandatory	Supported	Remarks
Query	Request parameter	TableName	Yes	Yes	-
		AttributesToGet	No	No	Deprecated parameter. For details, see ProjectionExpression.
		ConditionalOperator	No	No	Deprecated parameter. For details, see ProjectionExpression.
		ConsistentRead	No	No	Default strong consistency
		ExclusiveStartKey	No	Yes	-
		ExpressionAttributeNames	No	Yes	-
		ExpressionAttributeValues	No	Yes	-
		FilterExpression	No	Yes	-
		IndexName	No	Yes	-
		KeyConditionExpression	No	Yes	-
		KeyConditions	No	No	Deprecated parameter. For details, see KeyConditionExpression.
		Limit	No	Yes	-
		ProjectionExpression	No	Yes	-
		QueryFilter	No	No	Deprecated parameter. For details, see FilterExpression.
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
		ScanIndexForward	No	Yes	-
		Select	No	Yes	COUNT is not supported.
	Response parameter	ConsumedCapacity	-	No	Billing parameter, which is not supported
		Count	-	Yes	-
		Items	-	Yes	-
		LastEvaluatedKey	-	Yes	-
		ScannedCount	-	Yes	-

**Table 14** Scan
API	Parameter		Mandatory	Supported	Remarks
Scan	Request parameter	TableName	Yes	Yes	-
		AttributesToGet	No	No	Deprecated parameter. For details, see ProjectionExpression.
		ConditionalOperator	No	No	Deprecated parameter. For details, see ConditionExpression.
		ConsistentRead	No	No	Default strong consistency
		ExclusiveStartKey	No	Yes	-
		ExpressionAttributeNames	No	Yes	-
		ExpressionAttributeValues	No	Yes	-
		FilterExpression	No	Yes	-
		IndexName	No	Yes	-
		Limit	No	Yes	-
		ProjectionExpression	No	Yes	-
		ReturnConsumedCapacity	No	No	Billing parameter, which is not supported
		ScanFilter	No	No	Deprecated parameter. For details, see FilterExpression.
		Segment	No	Yes	-
		Select	No	Yes	COUNT is not supported.
		TotalSegments	No	Yes	-
	Response parameter	ConsumedCapacity	No	No	Billing parameter, which is not supported
		Count	-	Yes	-
		Items	-	Yes	-
		LastEvaluatedKey	-	Yes	-
		ScannedCount	-	Yes	-

**Table 15** UpdateTimeToLive
API	Parameter		Mandatory	Supported	Remarks
UpdateTimeToLive	Request parameter	TableName	Yes	Yes	-
	Request parameter	TimeToLiveSpecification	Yes	Yes	-
	Response parameter	TimeToLiveSpecification	-	Yes	-

**Table 16** DescribeTimeToLive
API	Parameter		Mandatory	Supported	Remarks
DescribeTimeToLive	Request parameter	TableName	Yes	Yes	-
DescribeTimeToLive	Response parameter	TimeToLiveSpecification	-	Yes	-

Parent Topic: Service Overview

Previous topic: What Is GeminiDB DynamoDB-Compatible API?

Next topic: Instance Specifications

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