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https://issues.apache.org/jira/browse/ARROW-621?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Wes McKinney updated ARROW-621:
-------------------------------
Description:
For performance-sensitive dynamic dispatch, the current visitor pattern may be
suboptimal due to having two virtual function dispatches per invocation. For
example, we might have:
{code}
ArrayVisitor* visitor = ...;
RETURN_NOT_OK(array->Accept(visitor));
{code}
For certain types of visitors, it may be possible to create a reusable pattern
like:
{code:language=c++}
template <typename VISITOR>
Status VisitArrayInline(const Array& array, VISITOR* visitor) {
switch(array.type_id()) {
case UINT8:
return visitor->Visit(static_cast<const UInt8Array&>(array));
...
default:
break;
}
return Status::NotImplemented("Array type not implemented");
}
{code}
It would be useful to have an understanding of how this design pattern
realistically impacts performance in canonical Arrow use cases (e.g. IPC record
batch loading / unloading).
was:
For performance-sensitive dynamic dispatch, the current visitor pattern may be
suboptimal due to having two virtual function dispatches per invocation. For
example, we might have:
{code}
ArrayVisitor* visitor = ...;
RETURN_NOT_OK(array->Accept(visitor));
{code}
For certain types of visitors, it may be possible to create a reusable pattern
like:
{code:language=c++}
template <typename VISITOR>
Status VisitArrayInline(const Array& array, VISITOR* visitor) {
switch(array->type_id()) {
case UINT8:
return visitor->Visit(static_cast<const UInt8Array&>(array));
...
default:
break;
}
return Status::NotImplemented("Array type not implemented");
}
{code}
It would be useful to have an understanding of how this design pattern
realistically impacts performance in canonical Arrow use cases (e.g. IPC record
batch loading / unloading).
> [C++] Implement an "inline visitor" template that enables
> visitor-pattern-like code without virtual function dispatch
> ---------------------------------------------------------------------------------------------------------------------
>
> Key: ARROW-621
> URL: https://issues.apache.org/jira/browse/ARROW-621
> Project: Apache Arrow
> Issue Type: New Feature
> Components: C++
> Reporter: Wes McKinney
>
> For performance-sensitive dynamic dispatch, the current visitor pattern may
> be suboptimal due to having two virtual function dispatches per invocation.
> For example, we might have:
> {code}
> ArrayVisitor* visitor = ...;
> RETURN_NOT_OK(array->Accept(visitor));
> {code}
> For certain types of visitors, it may be possible to create a reusable
> pattern like:
> {code:language=c++}
> template <typename VISITOR>
> Status VisitArrayInline(const Array& array, VISITOR* visitor) {
> switch(array.type_id()) {
> case UINT8:
> return visitor->Visit(static_cast<const UInt8Array&>(array));
> ...
> default:
> break;
> }
> return Status::NotImplemented("Array type not implemented");
> }
> {code}
> It would be useful to have an understanding of how this design pattern
> realistically impacts performance in canonical Arrow use cases (e.g. IPC
> record batch loading / unloading).
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