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https://issues.apache.org/jira/browse/CASSANDRA-19985?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18101139#comment-18101139
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Brad Schoening commented on CASSANDRA-19985:
--------------------------------------------
[~arvindk12] the output looks good.
1) bug, validation is asymmetric between the two input paths:
* Line 2275: {{--mode}} has {{{}choices=['tabular','csv','json']{}}}, so
argparse rejects garbage.
* Line 2070: {{option_with_default(configs.get, 'ui', 'mode', 'tabular')}}
accepts *anything* from cqlshrc.
Standardizing the parsing with an enum class:
{code:java}
class OutputMode(str, Enum):
TABULAR = 'tabular'
CSV = 'csv'
JSON = 'json'
__str__ = str.__str__
@property
def is_machine_readable(self):
return self is not OutputMode.TABULAR
@classmethod
def parse(cls, value):
if isinstance(value, cls):
return value
try:
return cls(str(value).strip().lower())
except ValueError:
raise ValueError("Invalid output mode %r; expected one of: %s"
% (value, ', '.join(m.value for m in cls))){code}
Then line 296 becomes self.mode = OutputMode.parse(mode)
2) One thing I'd explicitly leave alone here: the `isinstance(printer,
JsonTablePrinter)` branch at line 1029. Thirty-odd lines of JSON-specific
formatting living in `print_static_result` rather than on the printer that owns
it is poor style, but fixing it properly means a polymorphic `format_row`
across all three printers and real test surface. Better as its own ticket than
as scope creep on this one. Same for converting `TablePrinter.factory`'s
dispatch to a mapping keyed on the enum. [this from Claude]
> Enhance CQLSH to support machine-readable output formatting
> -----------------------------------------------------------
>
> Key: CASSANDRA-19985
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19985
> Project: Apache Cassandra
> Issue Type: New Feature
> Components: CQL/Interpreter
> Reporter: Brad Schoening
> Assignee: Arvind Kandpal
> Priority: Normal
> Attachments: json_formatters_example.py, test_json_formatting.py
>
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> Existing CQLSH output formatting provides tabular formatting using grid-like
> separators and text alignment which is designed for user readability.
> When CQL is run for non-interactive tasks as part of a pipeline this
> formatting complicates the machine processing of the output. As an example,
> [Sqlite|https://www.sqlite.org/cli.html] has a command line flag -mode to
> switch between tablular, csv, and several other supported formats.
> This enhancement will provide a new mode argument which will initially offer
> tabular and csv output formats. Tabular will remain the default so there will
> be no change for existing users. In the future, other modes such as json and
> insert could be added.
> {noformat}
> --mode={tabular, csv}
> Specify an output display format. The default is tabular.
> {noformat}
> The existing Copy To can be used for exporting to CSV, but it doesn't allow
> for query criteria and thus isn't a general solution for this issue.
> In cqlshmain.py, the EXPAND CQLSH option which uses print_formatted_result()
> for result output is an example of alternative formatting.
> Paging will have to be properly managed. A good formatter should handle a
> stream of rows rather than requiring the entire list in memory, especially
> for large SELECT * queries.
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