pyflink.table.expression.Expression.json_value

Expression.json_value(path: str, returning_type: pyflink.table.types.DataType = VarCharType(2147483647, true), on_empty: pyflink.table.expression.JsonValueOnEmptyOrError = JsonValueOnEmptyOrError.NULL, default_on_empty: Optional[Any] = None, on_error: pyflink.table.expression.JsonValueOnEmptyOrError = JsonValueOnEmptyOrError.NULL, default_on_error: Optional[Any] = None) → pyflink.table.expression.Expression

Extracts a scalar from a JSON string.

This method searches a JSON string for a given path expression and returns the value if the value at that path is scalar. Non-scalar values cannot be returned. By default, the value is returned as DataTypes.STRING(). Using returningType a different type can be chosen, with the following types being supported:

• STRING

• BOOLEAN

• INT

• DOUBLE

For empty path expressions or errors a behavior can be defined to either return null, raise an error or return a defined default value instead.

seealso:: json_query()

Examples:

>>> lit('{"a": true}').json_value('$.a') # STRING: 'true'
>>> lit('{"a.b": [0.998,0.996]}').json_value("$.['a.b'][0]",                     DataTypes.DOUBLE()) # DOUBLE: 0.998
>>> lit('{"a": true}').json_value('$.a', DataTypes.BOOLEAN()) # BOOLEAN: True
>>> lit('{"a": true}').json_value('lax $.b',                     JsonValueOnEmptyOrError.DEFAULT, False) # BOOLEAN: False
>>> lit('{"a": true}').json_value('strict $.b',                     JsonValueOnEmptyOrError.NULL, None,                     JsonValueOnEmptyOrError.DEFAULT, False) # BOOLEAN: False

New in version 1.12.0.