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Posted to dev@flink.apache.org by "cpugputpu (Jira)" <ji...@apache.org> on 2020/03/02 14:28:00 UTC

[jira] [Created] (FLINK-16385) Use LinkedHashMap in SqlFunctionUtils.java

cpugputpu created FLINK-16385:
---------------------------------

             Summary: Use LinkedHashMap in SqlFunctionUtils.java
                 Key: FLINK-16385
                 URL: https://issues.apache.org/jira/browse/FLINK-16385
             Project: Flink
          Issue Type: Test
          Components: Table SQL / Runtime
            Reporter: cpugputpu


The tests in _org.apache.flink.table.planner.expressions.ScalarFunctionsTest#testStringToMap_ can fail due to a different iteration order of a HashMap. The failure is presented as follows.

[ERROR] testStringToMap(org.apache.flink.table.planner.expressions.ScalarFunctionsTest)
org.junit.ComparisonFailure: Wrong result for: [STR_TO_MAP(f46)] optimized to: [STR_TO_MAP($46)] 
expected:<\{test1=1, test2=2, test3=3}> but was:<\{test2=2, test1=1, test3=3}>

 

The root cause of this failure lies in a HashMap initialized in _flink-table/flink-table-runtime-blink/src/main/java/org/apache/flink/table/runtime/functions/SqlFunctionUtils.java_ and a brief stack trace of the HashMap's iterator is presented for your reference:

_java.util.HashMap$EntrySet.iterator(HashMap.java:1014)_
_org.apache.flink.table.dataformat.DataFormatConverters$MapConverter.toBinaryMap(DataFormatConverters.java:1174)_
_org.apache.flink.table.dataformat.DataFormatConverters$MapConverter.toInternalImpl(DataFormatConverters.java:1157)_
_org.apache.flink.table.dataformat.DataFormatConverters$MapConverter.toInternalImpl(DataFormatConverters.java:1114)_
_org.apache.flink.table.dataformat.DataFormatConverters$DataFormatConverter.toInternal(DataFormatConverters.java:290)_
_TestFunction$144.map(Unknown Source)_
_org.apache.flink.table.planner.expressions.utils.ExpressionTestBase.evaluateExprs(ExpressionTestBase.scala:152)_

 

The specification about HashMap says that "this class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time". The documentation is here for your reference: https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html

 

The fix is to use LinkedHashMap instead of HashMap. In this way, the test will not suffer from the failure any more and the code will be more stable, free of this non-deterministic behaviour.

 

 



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