Re: Logical Replication of sequences

[Amit Kapila]

On Mon, Jan 19, 2026 at 6:36 PM vignesh C <vignes...@gmail.com> wrote:
>
> pg_get_sequence_data() internally uses try_relation_open() rather than
> relation_open(). As a result, if the target sequence no longer exists
> at the time of access, the function does not raise an error and
> instead returns NULLs for the sequence state columns. The sequence
> sync worker code previously assumed these columns to be non NULL and
> asserted accordingly. This assumption does not hold in the presence of
> concurrent DDL. The patch updates the sequence sync logic to
> explicitly check for NULL values returned from pg_get_sequence_data().
> If any of the required sequence state fields are NULL, the sequence
> sync worker skips processing that sequence to identify and report the
> missing sequences. The attached patch has the changes for the same.
>

- seqinfo_local->last_value = DatumGetInt64(slot_getattr(slot, ++col, &isnull));
- Assert(!isnull);
+ /*
+ * If the sequence was dropped concurrently, pg_get_sequence_data() can
+ * return NULLs.
+ */
+ datum = slot_getattr(slot, ++col, &isnull);
+ if (isnull)
+ return COPYSEQ_SKIPPED;
+ seqinfo_local->last_value = DatumGetInt64(datum);

- seqinfo_local->is_called = DatumGetBool(slot_getattr(slot, ++col, &isnull));
- Assert(!isnull);
+ datum = slot_getattr(slot, ++col, &isnull);
+ if (isnull)
+ return COPYSEQ_SKIPPED;
+ seqinfo_local->is_called = DatumGetBool(datum);

Is there a case where the first one (last_value) is non-null but later
can be null? If not, then I think it is better to retain assert for
other cases.


-- 
With Regards,
Amit Kapila.