On Wed, Apr 16, 2025 at 6:51 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Or we could do what Jian suggested and just not emit any dropStmt
> for child indexes. I continue to fear that that will have
> undesirable side-effects, but I have to admit that I'm not sure
> what. The fact that the backend will automatically drop the
> child index if we drop either its parent index or its table
> seems to cover a lot of the edge cases ... but does it cover
> all of them?
>
If pg_dump not produce "DROP INDEX IF EXISTS child_index;"
then we are actually tests drop parent index will cascade to child index.
If it fails, then execute pg_dump output, CREATE INDEX on child table will fail,
error message be like:
ERROR: relation "t_a_idx" already exists
CREATE TABLE tp(c int, a int, b int) PARTITION BY RANGE (b);
CREATE TABLE tp_1(c int, a int, b int);
ALTER TABLE tp ATTACH PARTITION tp_1 FOR VALUES FROM (0) TO (1);
CREATE INDEX t_a_idx ON tp_1(a);
CREATE INDEX tp_a_idx ON tp(a);
in this case, the partition index and partitioned index dependency
relationship is
DEPENDENCY_PARTITION_PRI.
per https://www.postgresql.org/docs/current/catalog-pg-depend.html
"
Example: a child partitioned index is made partition-dependent on both the
partition table it is on and the parent partitioned index, so that it goes away
if either of those is dropped, but not otherwise. The dependency on the parent
index is primary, so that if the user tries to drop the child partitioned index,
the error message will suggest dropping the parent index instead (not the
table).
"
from the doc, drop the partitioned index will cascade and also drop
the partition index.
On Tue, Apr 15, 2025 at 3:08 PM Pavel Stehule <pavel.stehule@gmail.com> wrote:
>
>
> There is a question why dump exports DROP INDEX, although the index will be dropped implicitly when table is dropped.
>
> So your fix can work, because all indexes will be dropped by DROP TABLE, but on second hand it is not consistent with
thecurrent behavior of pg_dump, where indexes are dropped explicitly.
>
> I have not knowledge, why pg_dump exports DROP INDEX explicitly, although it is redundant.
>
> Regards
>
> Pavel
>
if you specify ``--section=post-data``, then only the index command
will be generated.
so we actually do need separate dump exports DROP INDEX.
