I think the confusion is why ${var_name} (without the VAR prefix) is
considered as an error, especially if we only support ${VAR:var_name}.
[localhost:21000] default> -- ${hello}
select 1;
Error: Unknown substitution syntax (HELLO). Use ${VAR:var_name}
The workaround is rather trivial that is to escape it.
[localhost:21000] default> -- \${hello}
select 1;
Query: -- \${hello}
select 1
I also agree that unset variables should still be treated as an error
regardless where they're located whether in comments or non-comments.
Escaping should be use to ignore variable substitutions.
On Tue, Jun 26, 2018 at 7:36 AM Csaba Ringhofer <[email protected]>
wrote:
> >fixed in a manner that would still allow query hints
> I would vote for this.
> A possible solution could be to replace variables in comments only if the
> variable is set (so no longer treat it as an error). Referencing unset
> variables in non-comment code should be still treated as an error.
> This would not break any existing queries, and the only problematic side
> effect would be that "mistyped variables that should be hints" would be
> harder to detect, but that should be a very rare issue.
> I checked Hive shell and replaces it variables only if they are set, even
> in non-comment code, but I think that it is better to treat this as en
> error.
>
> > fixed for all comments in variables
> I would not go this way, as it could break some existing use cases. This
> should be very rare, but as the original issue seems like a minor nuisance
> to me, I think that it would be better to leave it as it is than to
> introduce a breaking change.
>
> On Mon, Jun 25, 2018 at 9:01 PM, Tim Armstrong <[email protected]>
> wrote:
>
>> What is the original motivation for the JIRA? Is there a use case where
>> the current behaviour is a problem?
>>
>> On Mon, Jun 25, 2018 at 11:38 AM, Adam Holley <[email protected]>
>> wrote:
>>
>>> Hello all,
>>>
>>> There is a Jira (https://issues.apache.org/jira/browse/IMPALA-3956) to
>>> change Impala so that variables within comments are not replaced. However,
>>> since Impala can use query hints in comments, fixing this as stated removes
>>> the ability to use hints through variables. Does the community think this
>>> should be fixed for all comments in variables, left alone, fixed in a
>>> manner that would still allow query hints, or some other alternative?
>>>
>>> Thanks.
>>>
>>>
>>> --
>>> *Adam Holley* | Engineering
>>> t. (512) 484-4060
>>> cloudera.com <https://www.cloudera.com>
>>>
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>>>
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>>>
>>
>>
>
