Re: Don't treate IndexStmt like AlterTable when DefineIndex is called from ProcessUtilitySlow.
| От | 正华吕 |
|---|---|
| Тема | Re: Don't treate IndexStmt like AlterTable when DefineIndex is called from ProcessUtilitySlow. |
| Дата | |
| Msg-id | CANerzAcS9Sd1Z0NZFirLr6ceorq1cVoEpQ-PrNq66pA4y1XY3A@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Don't treate IndexStmt like AlterTable when DefineIndex is called from ProcessUtilitySlow. (Tom Lane <tgl@sss.pgh.pa.us>) |
| Список | pgsql-hackers |
Hi, thanks a lot for your reply!
> Why do you think this is an improvement?
I hit the issue in Greenplum Database (Massively Parallel Postgres),
the MPP architecture is that coordinator dispatch statement to segments.
The dispatch logic is quit different for AlterTable and CreateTableLike:
* alter table: for each sub command, it will not dispatch; later it will dispatch
the alter table statement as a whole.
* for create table like statement, like `create table t (like t1 including indexes);`
this statement's 2nd stmt, has to dispatch to segments, but now it is treated
as alter table, the dispatch logic is broken for this case in Greenplum.
I look into the issue and Greenplum Database wants to keep align with Upstream
as possible. That is why I ask if we can force it to false.
Best,
Zhenghua Lyu
Tom Lane <tgl@sss.pgh.pa.us> 于2022年11月18日周五 06:26写道：
正华吕 <kainwen@gmail.com> writes:
> Recently read the code, I find that when calling DefineIndex
> from ProcessUtilitySlow, is_alter_table will be set true if
> this statement is came from expandTableLikeClause.
Yeah.
> Based on the above, I think we can always a false value
> for is_alter_table when DefineIndex is called from
> ProcessUtilitySlow.
Why do you think this is an improvement? Even if it's correct,
the code savings is so negligible that I'm not sure I want to
expend brain cells on figuring out whether it's correct. The
comment you want to remove does not suggest that it's optional
which value we should pass, so I think the burden of proof
is to show that this patch is okay not that somebody else
has to demonstrate that it isn't.
regards, tom lane
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