Return Postgres Arrays as Type 'arrayValue'

I know there’s some other discussion regarding Postgres arrays but this seemed to warrant a separate ticket.

Currently if I retrieve a column from Postgres of type _text (text array), the returned metadata for the column using local-data-api looks like:

{'arrayBaseColumnType': 0, 'isAutoIncrement': False, 'isCaseSensitive': True, 'isCurrency': False, 'isSigned': False, 'label': 'container_type', 'name': 'container_type', 'nullable': 0, 'precision': 2147483647, 'scale': 0, 'schemaName': '', 'tableName': 'required_attributes', 'type': 12, 'typeName': 'text'}

Notice ‘typeName’ returning text instead of _text. When deployed on AWS, Data API returns for the same column:

{'arrayBaseColumnType': 0, 'isAutoIncrement': False, 'isCaseSensitive': True, 'isCurrency': False, 'isSigned': False, 'label': 'attributes', 'name': 'attributes', 'nullable': 1, 'precision': 2147483647, 'scale': 0, 'schemaName': '', 'tableName': 'required_attributes', 'type': 2003, 'typeName': '_text'}

Notice ‘typeName’ indeed reflects the Postgres type _text.

This behavior continues with respect to the payload returned from the database, where local-data-api will return the value of the column as

{'stringValue': '{Volume}'}

where ‘Volume’ is the single item in the Postgres array. Meanwhile on AWS, Data API will return the following as value for the column:

{'arrayValue': {'stringValues': ['Volume']}}

Data API’s awareness of Postgress arrays seems to be better during read than during write!

I’m using:

• boto3
• Postgres 10.x
• Python 3.7

In code terms, the difference is captured in the two functions I maintain for local versus deployed Data API:

# Local Data API emulation currently returns arrays from database differently than
# AWS Data API, so let's establish at instantiation which function is doing our parsing.
def parse_array_local(field: Dict):
    """When running locally, parse string representation of array/set."""

    return next(iter(field.values())).lstrip('{').rstrip('}').split(',')


def parse_array_deployed(field: Dict):
    """When running on AWS, return nicely formatted - albeit nested - list."""

    return next(iter(field.values()))['stringValues']

Thank you, again. -jeff

[ormu5]

This looks good! I tried with text/int/float arrays in Postgres and received the following correct column metadata:

'columnMetadata': [
{'arrayBaseColumnType': 0, 'isAutoIncrement': False, 'isCaseSensitive': True, 'isCurrency': False, 'isSigned': False, 'label': 'name', 'name': 'name', 'nullable': 0, 'precision': 2147483647, 'scale': 0, 'schemaName': '', 'tableName': 'attributes', 'type': 12, 'typeName': 'text'}, 
{'arrayBaseColumnType': 0, 'isAutoIncrement': False, 'isCaseSensitive': True, 'isCurrency': False, 'isSigned': False, 'label': 'attributes', 'name': 'attributes', 'nullable': 1, 'precision': 2147483647, 'scale': 0, 'schemaName': '', 'tableName': 'attributes', 'type': 2003, 'typeName': '_text'}, 
{'arrayBaseColumnType': 0, 'isAutoIncrement': False, 'isCaseSensitive': False, 'isCurrency': False, 'isSigned': True, 'label': 'testing_int_array', 'name': 'testing_int_array', 'nullable': 1, 'precision': 10, 'scale': 0, 'schemaName': '', 'tableName': 'attributes', 'type': 2003, 'typeName': '_int4'}, 
{'arrayBaseColumnType': 0, 'isAutoIncrement': False, 'isCaseSensitive': False, 'isCurrency': False, 'isSigned': True, 'label': 'testing_float_array', 'name': 'testing_float_array', 'nullable': 1, 'precision': 17, 'scale': 17, 'schemaName': '', 'tableName': 'attributes', 'type': 2003, 'typeName': '_float8'}
]

Note ‘typeName’ having notation of ‘_<type>’.

And corresponding payload returned looks good, too, a couple of my test records being:

[{'stringValue': 'Thing'}, {'arrayValue': {'stringValues': ['Attribute']}}, {'arrayValue': {'longValues': [1, 3]}}, {'arrayValue': {'doubleValues': [1.231, 3.231]}}], 
[{'stringValue': 'Another Thing'}, {'arrayValue': {'stringValues': ['Attribute']}}, {'arrayValue': {'longValues': [1, 3]}}, {'arrayValue': {'doubleValues': [1.231, 3.231]}}]

Note arrays correctly in ‘arrayValue’ object whose nested object correctly has Data API type for key and value of properly-parsed values as list.

[ormu5]

Busy week this week, happy to look at this soon, though.