[
https://issues.apache.org/jira/browse/METRON-1618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16514843#comment-16514843
]
ASF GitHub Bot commented on METRON-1618:
----------------------------------------
GitHub user cestella opened a pull request:
https://github.com/apache/metron/pull/1063
METRON-1618: Stellar boolean expressions should treat missing variables as
false
## Contributor Comments
Right now, because fields may not exist, users can have an awkward time.
For instance, checking for is_alert, you end up having to preface checks with
exists(is_alert).
For instance, in one of our
[use-cases](https://github.com/apache/metron/tree/master/use-cases/geographic_login_outliers)
we use
```
"is_alert := exists(is_alert) && is_alert",
"is_alert := is_alert || (geo_outlier != null && geo_outlier == true)"
```
instead of :
```
"is_alert := is_alert || geo_outlier == true"
```
I suggest that we adopt a convention from javascript whereby we assume a
field not existing or being null should act as false in boolean expressions.
This will simplify stellar's use and hopefully result in less awkwardness.
You can test this via the REPL. This is what I did, in addition to unit
tests:
```
{12:48}[system]~/Documents/workspace/metron/fork/incubator-metron:stellar_falsey
✓ ➭ mvn exec:java
-Dexec.mainClass="org.apache.metron.stellar.common.shell.cli.StellarShell" -pl
metron-stellar/stellar-common
[INFO] Scanning for projects...
[INFO]
[INFO]
------------------------------------------------------------------------
[INFO] Building stellar-common 0.5.0
[INFO]
------------------------------------------------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.6.0:java (default-cli) @ stellar-common ---
log4j:WARN No appenders could be found for logger
(org.apache.metron.stellar.common.shell.DefaultStellarShellExecutor).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for
more info.
Stellar, Go!
Functions are loading lazily in the background and will be unavailable
until loaded fully.
{}
[Stellar]>>> is_alert || null
false
[Stellar]>>> NOT(is_alert)
true
[Stellar]>>> is_alert
[Stellar]>>> if is_alert then 'alert' else 'not'
not
[Stellar]>>> if is_alert || true then 'alert' else 'not'
alert
[Stellar]>>> MAP_GET(is_alert, { false : 'blah', true : 'foo' })
[Stellar]>>>
```
## Pull Request Checklist
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### For all changes:
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```
- [x] Have you written or updated unit tests and or integration tests to
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### For documentation related changes:
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#### Note:
Please ensure that once the PR is submitted, you check travis-ci for build
issues and submit an update to your PR as soon as possible.
It is also recommended that [travis-ci](https://travis-ci.org) is set up
for your personal repository such that your branches are built there before
submitting a pull request.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/cestella/incubator-metron stellar_falsey
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/metron/pull/1063.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 #1063
----
commit fc215e76500a23b1da20ae189a2f5db35c076786
Author: cstella <cestella@...>
Date: 2018-06-16T16:31:35Z
Make false be null in boolean expressions
commit 95929c072798e0700231657903f12e0590280890
Author: cstella <cestella@...>
Date: 2018-06-16T16:33:29Z
additional tests
----
> Stellar boolean expressions should treat missing variables as false
> -------------------------------------------------------------------
>
> Key: METRON-1618
> URL: https://issues.apache.org/jira/browse/METRON-1618
> Project: Metron
> Issue Type: Improvement
> Reporter: Casey Stella
> Priority: Major
>
> Currently, we treat missing variables as null in boolean expressions rather
> than false. If we did adopted a more javascripty approach, stellar would be
> easier to use and require fewer existence checks.
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