[jira] [Resolved] (FLINK-4241) Cryptic expression parser exceptions

["Timo Walther (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-4241?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Timo Walther resolved FLINK-4241.
---------------------------------
       Resolution: Fixed
    Fix Version/s: 1.2.0

Fixed in ef15984988e883ced5311b332e5e5d8521c9573f.

> Cryptic expression parser exceptions
> ------------------------------------
>
>                 Key: FLINK-4241
>                 URL: https://issues.apache.org/jira/browse/FLINK-4241
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>    Affects Versions: 1.1.0
>            Reporter: Till Rohrmann
>            Assignee: Timo Walther
>             Fix For: 1.2.0
>
>
> The exceptions thrown when giving wrong SQL syntax to Flink's SQL parser is very cryptic and should be improved. For example, the following code snippet:
> {code}
> inputTable.filter("a == 0");
> {code}
> gives the following exception:
> {code}
> Exception in thread "main" org.apache.flink.api.table.ExpressionParserException: Could not parse expression: [1.4] failure: `-' expected but `=' found
> a == 0
>    ^
> 	at org.apache.flink.api.table.expressions.ExpressionParser$.parseExpression(ExpressionParser.scala:355)
> 	at org.apache.flink.api.table.Table.filter(table.scala:161)
> 	at com.dataartisans.streaming.SimpleTableAPIJob.main(SimpleTableAPIJob.java:32)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> 	at java.lang.reflect.Method.invoke(Method.java:497)
> 	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
> {code}
> From this description it is very hard to understand that {{==}} is not a valid operator.
> Another example is:
> {code}
> inputTable.select("*");
> {code}
> which gives
> {code}
> Exception in thread "main" org.apache.flink.api.table.ExpressionParserException: Could not parse expression: Base Failure
> 	at org.apache.flink.api.table.expressions.ExpressionParser$.parseExpressionList(ExpressionParser.scala:342)
> 	at org.apache.flink.api.table.Table.select(table.scala:103)
> 	at com.dataartisans.streaming.SimpleTableAPIJob.main(SimpleTableAPIJob.java:33)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> 	at java.lang.reflect.Method.invoke(Method.java:497)
> 	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
> {code}
> I think it would considerably improve user experience if we print more helpful parsing exceptions.



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