[
https://issues.apache.org/jira/browse/CALCITE-4191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17184958#comment-17184958
]
Julian Hyde commented on CALCITE-4191:
--------------------------------------
[~Chunwei Lei], There is already a way - but it's indirect. Use a
{{RelBuilder}}. As an example of code that does this, see
[AggregateExtractProjectRule|https://github.com/apache/calcite/blob/885a3da76cfd59171624dc569e83e93a5bdaffe3/core/src/main/java/org/apache/calcite/rel/rules/AggregateExtractProjectRule.java#L126]:
{code:java}
final List<RelBuilder.AggCall> newAggCallList = new ArrayList<>();
for (AggregateCall aggCall : aggregate.getAggCallList()) {
final ImmutableList<RexNode> args =
relBuilder.fields(
Mappings.apply2(mapping, aggCall.getArgList()));
final RexNode filterArg = aggCall.filterArg < 0 ? null
: relBuilder.field(Mappings.apply(mapping, aggCall.filterArg));
newAggCallList.add(
relBuilder.aggregateCall(aggCall.getAggregation(), args)
.distinct(aggCall.isDistinct())
.filter(filterArg)
.approximate(aggCall.isApproximate())
.sort(relBuilder.fields(aggCall.collation))
.as(aggCall.name));
}
final RelBuilder.GroupKey groupKey =
relBuilder.groupKey(newGroupSet, newGroupSets);
relBuilder.aggregate(groupKey, newAggCallList);
call.transformTo(relBuilder.build());
{code}
Those {{RelBuilder.AggCall}} objects are basically builders.
{{relBuilder.aggregate}} converts them into {{AggregateCall}} instances.
> Improve the logic of creating aggregate calls
> ---------------------------------------------
>
> Key: CALCITE-4191
> URL: https://issues.apache.org/jira/browse/CALCITE-4191
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Liya Fan
> Assignee: Liya Fan
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> According to the current code base, the only way to create \{{AggregateCall}}
> objects is by calling one of the two \{{AggregateCall#create}} methods (other
> create methods are deprecated).
> The two {{create}} methods have 9 and 11 parameters, respectively, 3 of which
> are booleans and 2 are ints. We find this makes the code less readable and
> error-prone, as some bugs are caused by specifying the wrong parameters.
> In this issue, we improve the related logic by the builder pattern, which
> results in the following benefits:
> 1. By creating the objects by the builder pattern, there is no need to
> maintain multiple overrides of the {{create}} methods.
> 2. There is no need to maintain multiple overrides of the {{copy}} methods,
> either.
> 3. The code becomes more readable and less error-prone, as it is less like to
> specify the wrong parameter.
> 4. Creating {{AggregateCall}} objects becomes easier, as the user does not
> have specify the default parameters repeatedly.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
