cpugputpu created FLINK-16385:
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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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