luoyuxia created FLINK-27145:
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Summary: The code generated for agg function accepts empty
parameters can't be compiled
Key: FLINK-27145
URL: https://issues.apache.org/jira/browse/FLINK-27145
Project: Flink
Issue Type: Bug
Components: Table SQL / Planner
Reporter: luoyuxia
Fix For: 1.16.0
In batch mode, when I try to call Hive's `count` function(GenericUDAFCount)
using the following sql:
{code:java}
select count(*) from src;
{code}
It'll throw the exception "Unexpected token ")" in primary" while compling the
generated code.
It happens in the following generated code:
{code:java}
function_org$apache$flink$table$planner$utils$xxx.accumulate(
acc$7,); {code}
The reason is the following code in method
`AggCodeGenHelper#genAccumulateFlatAggregateBuffer`
{code:java}
s"""
|$externalAccTypeTerm $externalAccTerm = $externalAccCode;
|${functionIdentifiers(function)}.accumulate(
| $externalAccTerm,
| ${operandTerms.mkString(", ")}); // but operandTerms can be empty list
|$aggBufferName = ${genToInternalConverter(ctx,
externalAccType)(externalAccTerm)};
|${aggBufferExpr.nullTerm} = false;
""".stripMargin {code}
In this case, for `count(*)`, it'll regards as an agg function with empty
parameter in Hive.
So, the exception happens.
Although the agg function with empty parameter is rare, it may happens. We
should make the code more rubst.
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