Re: [PATCH] Fix duplicate errmsg in ALTER TABLE SPLIT PARTITION - Mailing list pgsql-hackers

Hi,

Thanks for the detailed review.

On Tue, 21 Apr 2026 at 12:15, John Naylor <johncnaylorls@gmail.com> wrote:

On Tue, Apr 21, 2026 at 11:34 AM Ayush Tiwari
<ayushtiwari.slg01@gmail.com> wrote:


> Also, I think "can not" can be replaced with "cannot" for consistency
> throughout? Havent added is as part of this patch though. Thoughts?

Not just consistency, the first spelling is simply wrong, and this
isn't the only place.

Agreed. I've attached a v2 draft patch fixes all "can not" -> "cannot" occurrences across

the split/merge partition code: 

  - parse_utilcmd.c: "can not split DEFAULT partition" and
    "can not split non-DEFAULT partition"
  - partbounds.c: "can not merge partition ... together with ..." and
    "can not split to partition ... together with ..."
  - tablecmds.c: "can not find partition for split partition row"

Taking a brief look at the test files added for this feature

src/test/regress/sql/partition_merge.sql/.out
src/test/regress/sql/partition_split.sql/.out

...I noticed that the .sql file has "-- ERROR:" comments that are
exact copies of the error message, which can't be great for
maintenance. We don't seem to do that anywhere else, so I'm not sure
what the motivation was.

Good point. It make sense to remove "-- ERROR:", "-- DETAIL:", and
"-- HINT:" comment lines from both partition_split.sql and
partition_merge.sql (and their corresponding .out files). I've kept the Descriptive
comments like "-- (space between sections ...)" and

"-- sales_error intersects with ..." . Incorporated this too in patch.

Case in point, I noticed at least one other grammatical error in a message:

$ git grep 'DEFAULT partition should be one'
src/backend/parser/parse_utilcmd.c:       errmsg("DEFAULT partition
should be one"),
src/backend/po/de.po:msgid "DEFAULT partition should be one"
src/test/regress/expected/partition_split.out:-- ERROR  DEFAULT
partition should be one
src/test/regress/expected/partition_split.out:ERROR:  DEFAULT
partition should be one
src/test/regress/sql/partition_split.sql:-- ERROR  DEFAULT partition
should be one

Fixed: "DEFAULT partition should be one" is now

"cannot specify more than one DEFAULT partition".

 

That's makes four places that will need to be changed, instead of two,
and it's easy to overlook the comments.

While I'm looking,

ALTER TABLE sales_range SPLIT PARTITION sales_others INTO
  (PARTITION sales_dec2021 FOR VALUES FROM ('2021-12-01') TO ('2022-01-01'),
   PARTITION sales_error FOR VALUES FROM ('2021-12-30') TO ('2022-02-01'),
   PARTITION sales_feb2022 FOR VALUES FROM ('2022-02-01') TO ('2022-03-01'),
   PARTITION sales_others DEFAULT);

ERROR:  can not split to partition "sales_error" together with
partition "sales_dec2021"

This seems like it should be
ERROR: cannot split partition sales_others
DETAIL: partition "sales_error" overlaps with partition "sales_dec2021"

...or something like that, maybe others have a better idea, but I find
the current message confusing.

In short, I think there is a lot more here that needs attention.

Hmm, I changed the confusing "can not split to partition X
together with partition Y" messages (for both split and merge) to:

  errmsg: "cannot split non-adjacent partitions \"%s\" and \"%s\""
  errdetail: "Lower bound of partition \"%s\" is not equal to upper
              bound of partition \"%s\"."

  errmsg: "cannot merge non-adjacent partitions \"%s\" and \"%s\""
  errdetail: "Lower bound of partition \"%s\" is not equal to upper
              bound of partition \"%s\"."

I also removed the

now-redundant errhint lines ("ALTER TABLE ... SPLIT/MERGE PARTITION
requires the partition bounds to be adjacent.") since
the errmsg itself says "non-adjacent".

Additionally, the errhint for splitting a DEFAULT partition had a
grammar error: "To split DEFAULT partition one of the new partition
must be DEFAULT." is now "To split a DEFAULT partition, one of the new
partitions must be DEFAULT."

And of course the original fix: the duplicate errmsg() -> errdetail()
in transformPartitionCmdForSplit() with proper capitalization and

trailing period.