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https://issues.apache.org/jira/browse/CALCITE-1882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16444449#comment-16444449
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Julian Hyde commented on CALCITE-1882:
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Other people besides me can review. Can you ask for reviewers on the dev list.
> Can't obtain the user defined aggregate function such as sum,avg by calcite
> ---------------------------------------------------------------------------
>
> Key: CALCITE-1882
> URL: https://issues.apache.org/jira/browse/CALCITE-1882
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.12.0
> Reporter: yuemeng
> Assignee: yuemeng
> Priority: Critical
>
> If we want to register a sum or avg aggregate function to deal with different
> data type such as sum(double) ,we implement a SqlUserDefinedAggFunction and
> register with name sum,but when we execute a sql like:
> {code}
> select id,sum(payment) from table test group by id
> {code}
> in fact,it always give the SqlSumAggFunction function which builtin by
> calcite,never find the exactly function which we register by ourself.
> During sql parse process,method createCall in SqlAbstractParserImpl will be
> called,
> {code}
> protected SqlCall createCall(
> SqlIdentifier funName,
> SqlParserPos pos,
> SqlFunctionCategory funcType,
> SqlLiteral functionQualifier,
> SqlNode[] operands) {
> SqlOperator fun = null;
> // First, try a half-hearted resolution as a builtin function.
> // If we find one, use it; this will guarantee that we
> // preserve the correct syntax (i.e. don't quote builtin function
> /// name when regenerating SQL).
> if (funName.isSimple()) {
> final List<SqlOperator> list = Lists.newArrayList();
> opTab.lookupOperatorOverloads(funName, funcType, SqlSyntax.FUNCTION,
> list);//we lookup in SqlStdOperatorTable,and always find buidin function for
> sum ,avg .eg
> if (list.size() == 1) {
> fun = list.get(0);
> }
> }
> // Otherwise, just create a placeholder function. Later, during
> // validation, it will be resolved into a real function reference.
> if (fun == null) {
> fun = new SqlUnresolvedFunction(funName, null, null, null, null,
> funcType);
> }
> return fun.createCall(functionQualifier, pos, operands);
> }
> {code}
> but the problem will be appear in deriveType,because of we get the
> SqlSumAggFunction previously,and the sqlKind of SqlSumAggFunction is AVG,but
> the sqlKind of sql user defined agg function (sum) which we register by
> ourself is OTHER_FUNCTION,so it filter out our sum function.
> {code}
> private static Iterator<SqlOperator>
> filterOperatorRoutinesByKind(Iterator<SqlOperator> routines,
> final SqlKind sqlKind) {
> return Iterators.filter(routines,
> new PredicateImpl<SqlOperator>() {
> public boolean test(SqlOperator input) {
> return input.getKind() == sqlKind;
> }
> });
> }
> {code}
> that cause we never obtain sum function which registered by user .
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