ApsaraDB for MongoDB:Compatibility details of DynamoDB-compatible instances

Table operations

Item operations

Query and Scan operations

Attribute names containing a period (.)

In Amazon DynamoDB, an attribute name containing . is treated as a scalar attribute when the expression attribute name maps to all elements in a document path, or as a nested attribute otherwise. In ApsaraDB for MongoDB, scalar attributes containing . cannot be processed in query or projection expressions.

Projection expressions

Only one-dimensional arrays are supported. When a projection expression references a single array element, all other fields are also returned.

Condition expressions

The DynamoDB condition expression syntax is supported with the following constraints:

condition-expression ::=
      operand comparator operand
    | operand BETWEEN operand AND operand
    | operand IN ( operand (',' operand (, ...) ))
    | function
    | condition AND condition
    | condition OR condition
    | NOT condition
    | ( condition )

comparator ::=
    =
    | <>
    | <
    | <=
    | >
    | >=

function ::=
    attribute_exists (path)
    | attribute_not_exists (path)
    | attribute_type (path, type)
    | begins_with (path, substr)
    | contains (path, operand)
    | size (path)

Constraints:

• operand1 comparator operand2: operand1 must be a path; operand2 must be an expression attribute value.

• operand1 BETWEEN operand2 AND operand3: operand1 must be a path; all other operands must be expression attribute values.

• operand1 IN (operand2, ...): operand1 must be a path; all other operands must be expression attribute values.

• size(path): path must be of the STRING type (for length) or SET/LIST type (for size). BINARY and MAP types are not supported.

Update expressions

The DynamoDB update expression syntax is supported with the following constraints:

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

SET action constraints:

• SET path = operand: operand cannot be a path.

• SET path = operand1 + operand2 or SET path = operand1 - operand2: operand1 must be a path. Only field increment and decrement are supported.

• SET path = if_not_exists(path, value): Both path references must be equal, and value must be an expression attribute value. Partial updates are not supported when multiple conditions are specified concurrently — all conditions must be met for the expression to execute.

• SET path = list_append(list1, list2): One of list1 or list2 must equal path; the other must be an expression attribute value.

REMOVE action constraint:

When a list element is removed, null replaces it. The list size remains unchanged and remaining elements are not shifted.