Update a row

Use Tablestore SDK for Python to add, modify, or delete attribute columns in a row and optionally specify data versions.

Prerequisites

Install the Tablestore SDK for Python and initialize a client.

Function description

Call update_row to update a row by primary key. The method changes only the specified attribute columns and leaves other attribute columns unchanged.

def update_row(
    self,
    table_name,
    row,
    condition,
    return_type=None,
    transaction_id=None,
)

The following example changes the status attribute column to offline for the row whose primary key is ("device", 1) in example_table.

primary_key = [("partition", "device"), ("id", 1)]
attribute_columns = {"PUT": [("status", "offline")]}
row = Row(primary_key, attribute_columns)
condition = Condition(RowExistenceExpectation.EXPECT_EXIST)

consumed, return_row = client.update_row(
    "example_table",
    row,
    condition,
)
print("Write CU: %s" % consumed.write)

Parameters

The update_row method contains the following parameters.

Name	Type	Description
table_name (required)	`str`	The name of the table.
row (required)	`Row`	The primary key and attribute column changes.
condition (required)	`Condition`	The update condition. For more information, see Use conditional updates. To skip row and column value checks, specify `Condition(RowExistenceExpectation.IGNORE)`.
return_type (optional)	`ReturnType`	The return type. `RT_NONE`, the default value, returns no data. `RT_PK` returns the primary key.
transaction_id (optional)	`str`	The local transaction ID. Specify this parameter only for updates in a local transaction. For more information, see Use local transactions.

Row data

The row parameter is of the Row type and contains the following parameters.

Name	Type	Description
primary_key (required)	`List[Tuple]`	The primary key. Specify all primary key columns. Their names, order, number, and types must match the primary key schema of the table.
attribute_columns (required)	`Dict[str, List]`	The attribute column changes. `PUT` adds or modifies attribute columns. `DELETE` deletes specified versions. `DELETE_ALL` deletes all versions of attribute columns. `INCREMENT` performs atomic counter operations on integer attribute columns.

Response

update_row returns the following values.

Field	Type	Description
consumed	`CapacityUnit`	The read and write CUs consumed by the operation.
return_row	`Row`	The returned row. If `return_type` is `RT_PK`, the primary key is returned. Otherwise, this value is `None`.

Examples

Write an attribute column with a specified version

The third element of an attribute column tuple in a PUT operation specifies the data version as a timestamp in milliseconds.

timestamp = int(time.time() * 1000)
primary_key = [("partition", "device"), ("id", 1)]
attribute_columns = {
    "PUT": [("status", "online", timestamp)],
}
row = Row(primary_key, attribute_columns)

client.update_row(
    "example_table",
    row,
    Condition(RowExistenceExpectation.EXPECT_EXIST),
)

Delete a specified version of an attribute column

The following example deletes the version identified by timestamp from the status attribute column and retains other versions.

primary_key = [("partition", "device"), ("id", 1)]
attribute_columns = {
    "DELETE": [("status", None, timestamp)],
}
row = Row(primary_key, attribute_columns)

client.update_row(
    "example_table",
    row,
    Condition(RowExistenceExpectation.EXPECT_EXIST),
)

Delete an entire attribute column

The following example deletes all versions of the status attribute column.

primary_key = [("partition", "device"), ("id", 1)]
attribute_columns = {"DELETE_ALL": ["status"]}
row = Row(primary_key, attribute_columns)

client.update_row(
    "example_table",
    row,
    Condition(RowExistenceExpectation.EXPECT_EXIST),
)