Re: [POC] Fast COPY FROM command for the table with foreign partitions

Hi Alexey,

On Tue, Sep 8, 2020 at 6:29 PM Alexey Kondratov
<a(dot)kondratov(at)postgrespro(dot)ru> wrote:
> On 2020-09-08 10:34, Amit Langote wrote:
> > Any thoughts on the taking out the refactoring changes out of the main
> > patch as I suggested?
> >
>
> +1 for splitting the patch. It was rather difficult for me to
> distinguish changes required by COPY via postgres_fdw from this
> refactoring.
>
> Another ambiguous part of the refactoring was in changing
> InitResultRelInfo() arguments:
>
> @@ -1278,6 +1280,7 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
> Relation resultRelationDesc,
> Index resultRelationIndex,
> Relation partition_root,
> + bool use_multi_insert,
> int instrument_options)
>
> Why do we need to pass this use_multi_insert flag here? Would it be
> better to set resultRelInfo->ri_usesMultiInsert in the
> InitResultRelInfo() unconditionally like it is done for
> ri_usesFdwDirectModify? And after that it will be up to the caller
> whether to use multi-insert or not based on their own circumstances.
> Otherwise now we have a flag to indicate that we want to check for
> another flag, while this check doesn't look costly.

Hmm, I think having two flags seems confusing and bug prone,
especially if you consider partitions. For example, if a partition's
ri_usesMultiInsert is true, but CopyFrom()'s local flag is false, then
execPartition.c: ExecInitPartitionInfo() would wrongly perform
BeginForeignCopy() based on only ri_usesMultiInsert, because it
wouldn't know CopyFrom()'s local flag. Am I missing something?

--
Amit Langote
EnterpriseDB: http://www.enterprisedb.com