On 2020-09-08 17:00, Amit Langote wrote:
Hi Alexey,
On Tue, Sep 8, 2020 at 6:29 PM Alexey Kondratov
<a.kondra...@postgrespro.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?
No, you're right. If someone want to share a state and use ResultRelInfo
(RRI) for that purpose, then it's fine, but CopyFrom() may simply
override RRI->ri_usesMultiInsert if needed and pass this RRI further.
This is how it's done for RRI->ri_usesFdwDirectModify.
InitResultRelInfo() initializes it to false and then
ExecInitModifyTable() changes the flag if needed.
Probably this is just a matter of personal choice, but for me the
current implementation with additional argument in InitResultRelInfo()
doesn't look completely right. Maybe because a caller now should pass an
additional argument (as false) even if it doesn't care about
ri_usesMultiInsert at all. It also adds additional complexity and feels
like abstractions leaking.
Regards
--
Alexey Kondratov
Postgres Professional https://www.postgrespro.com
Russian Postgres Company
