Re: Parallel INSERT (INTO ... SELECT ...)

On Mon, Mar 1, 2021 at 9:08 AM Greg Nancarrow <gregn4422(at)gmail(dot)com> wrote:
>
> Posting an updated set of patches that includes Amit Langote's patch
> to the partition tracking scheme...
> (the alternative of adding partitions to the range table needs further
> investigation)

I was reviewing your latest patch and I have a few comments.

In patch 0001
1.
+static bool
+target_rel_max_parallel_hazard_recurse(Relation rel,
+ CmdType command_type,
+ max_parallel_hazard_context *context)
+{
+ TupleDesc tupdesc;
+ int attnum;
+
+ /* Currently only CMD_INSERT is supported */
+ Assert(command_type == CMD_INSERT);
…….
+ /*
+ * Column default expressions and check constraints are only applicable to
+ * INSERT and UPDATE, but since only parallel INSERT is currently supported,
+ * only command_type==CMD_INSERT is checked here.
+ */
+ if (command_type == CMD_INSERT)

If we have an assert at the beginning of the function, then why do we
want to put the if check here?

2.
In patch 0004, We are still charging the parallel_tuple_cost for each
tuple, are we planning to do something about this? I mean after this
patch tuple will not be transferred through the tuple queue, so we
should not add that cost.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com