gobraves commented on issue #6983:
URL:
https://github.com/apache/arrow-datafusion/issues/6983#issuecomment-1660801140
hi @alamb, I apologize for the delayed response. Based on your tips, I
executed the following commands in the CLI and also ran the code you provided
to reproduce the issue. I noticed that executing the commands in the CLI was
almost 8 times faster than running the code mentioned above, which is
consistent with my CPU core count.
Here are the commands I executed in the CLI:
create external table test stored as parquet location 'part-0.parquet';
create table t as select * from test;
explain create table t as select * from test;
In the logical_plan of the explain output, I observed `CreateMemoryTable`
and `TableScan`. Consequently, I reviewed the code for `CreateMemoryTable` in
the datafusion-cli and the `.cache() ` function, hoping to identify the
differences. I noticed that the target_partitions are indeed passed in both
cases, but I'm unsure why they are not utilized in `.cache()`. However, from
the commit mentioned in issue #6984 , it seems that the problem is resolved by
using repartitioning. Therefore, it appears that the difference lies in one
implementation using `Partitioning`, while the other does not. However, when
browsing through the code myself, I couldn't find any relevant settings. If
this is the case, could you please provide some hints as to which part of the
code this operation occurs?
I have one more question: Do we need to create a new DmlStatement to address
this issue?
> Perhaps this could be done by creating a LogicalPlan::DmlStatement for
write and then letting the existing insert machinery work rather than doing a
custom "collect".
I'm not entirely clear about this statement, and I believe it might be
because I haven't fully grasped the problem described above.
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