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Posted to issues@metron.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2017/08/06 18:50:00 UTC
[jira] [Commented] (METRON-1090) STELLAR Add Assignment capability
to Stellar language
[ https://issues.apache.org/jira/browse/METRON-1090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16115897#comment-16115897 ]
ASF GitHub Bot commented on METRON-1090:
----------------------------------------
GitHub user ottobackwards opened a pull request:
https://github.com/apache/metron/pull/687
METRON-1090 [NO MERGE UNTIL METRON-711] Add Assignment to Stellar Language
This PR adds support for Assignment to the Stellar Language. It is dependent on [METRON-711](https://github.com/apache/metron/pull/686) before it can be merge.
I still need to do the doc work, and more testing.
## Concept
- Allow for assignment of values to variables only
- Assignment both returns the assigned value AND updates the variable
- VariableResolver implementation may or may not choose to support updates
- The Shell handles all assignments ( foo := 'val' ) as ("foo = 'val'"). Exposing the whole operation to Stellar allows catching illegal values and grammar
- The LambdaExpression does attempt to update variables, but this would have effect if the state was using a VariableResolver instance that supported updates AND the variable was not a 'lambda' variable.
```java
String expr = "MAP([ foo, bar, baz ], (item) -> count *= 2 )";
Map<String,Object> map = new HashMap<String,Object>(){{
put("foo",1);
put("bar",1);
put("baz",1);
put("count", 1);
}};
for(int i = 0 ; i < 5; i++){
run(expr, map);
}
Assert.assertEquals(new DecimalFormat("#").format(Math.pow(2,15)), map.get("count").toString());
```
Support for:
= , +=, -=, *=, /=
## Side effects:
This is opt-in for the resolvers. The MapVariableResolver does NOT support update, so there is no change to Enrichment, Parsers, Profile, and Shell ( beyond what has been mentioned ).
## Testing:
See BasicStellarTest:test*Assign() for some usages.
- Existing profiles, enrichments, parser transforms would work
- Run different statements in the shell ( including those that would have worked before like = := 6.
- more to come
> This PR is to get the concept as a proposal out for review and start the discussion. I will start a
> discuss thread as well.
---------
> Note: This PR resolves [METRON-693 : Stellar REPL lets reserved tokens be used as unusable variable names](https://issues.apache.org/jira/browse/METRON-693) as well.
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> and METRON-711
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#### Note:
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You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ottobackwards/metron stellar_assign
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/metron/pull/687.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #687
----
commit 215dc969026fa557a0a0f3efb9fe2bc170666b9a
Author: Otto Fowler <ot...@gmail.com>
Date: 2017-08-06T02:14:51Z
Do not set variables when exceptions are thrown from assignment.
Also remove executeStellar which is not required, if it doesn't eat the exception
commit f8e2fa9bdecd48fd70f03f2337439582ce341e21
Author: Otto Fowler <ot...@gmail.com>
Date: 2017-08-06T14:20:32Z
Adds Variable Assignment to the Stellar Lanaguage
=, +=, -=, *=, /=
This are valid for assignment to variables. All assignments return the value assigned,
as other scripting languages do.
VariableResolver extended with an update() method, though it may not be supported
by all resolvers, this gives the ability to update variables and save between calls.
The shell was updated for this, such that assignment calls
More testing need and doc but I wanted to get it out there.
This is dependent on PR 686
----
> STELLAR Add Assignment capability to Stellar language
> -----------------------------------------------------
>
> Key: METRON-1090
> URL: https://issues.apache.org/jira/browse/METRON-1090
> Project: Metron
> Issue Type: New Feature
> Reporter: Otto Fowler
> Assignee: Otto Fowler
>
> Add support for =, +=, -=, *=, /= for variables in stellar.
> foo = 5 returns 5 AND sets foo to 5 if the VariableResolver supports it.
> The shell should be changed to assign variables using this syntax, because exposing the left side to stellar allows catching errors for invalid keywords in left side.
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