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33 lines
1.3 KiB
Markdown
33 lines
1.3 KiB
Markdown
# Change The Owner Of A Sequence
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Sequence ownership is one of those things in PostgreSQL that is just under the
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surface and so it is easy to not know about it. If, however, you are doing a
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live migration where you are swapping out a column or entire table, you'll need
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to know about it.
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For instance, consider migrating a primary key column from `int` to `bigint`.
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Let's say you construct and backfill the new `bigint` column and then swap it
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out with the `int` column.
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Run a sequence ownership query like [the ones discussed in this
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article](https://sadique.io/blog/2019/05/07/viewing-sequence-ownership-information-in-postgres/)
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and you'll see that the original `int` column still owns the sequence.
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If you try to drop `old_id`, you'll fortunately get a warning from Postgres:
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```sql
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alter table cats drop column old_id;
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ERROR: cannot drop column old_id of table cats because other objects depend on it
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DETAIL: default value for column id of table cats depends on sequence cats_id_seq
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HINT: Use DROP ... CASCADE to drop the dependent objects too.
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```
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The `DROP ... CASCADE` suggestion is not the thing to do here. Instead, you'll
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want to update the ownership of the sequence to the _new_ `id` column:
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```sql
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alter sequence cats_id_seq owned by cats.id;
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```
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[source](https://www.postgresql.org/docs/current/sql-altersequence.html)
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