Re: Getting the currently used sequence for a SERIAL column

Hanne Moa schrieb am 19.10.2016 um 10:31:
>> You can use the following statement to find the sequences that a table uses:
>>
> Thanks. This assumes that there is only one nextval per table though.
> While this holds for the database we need this on right now, it's not a
> sufficiently generic solution. How do I, for the sake of paranoia,
> specify a column?

No, it will return that for all columns in that table that have a sequence default
If you add "col.attname" to the select list you can see each column.

create sequence s1;
create sequence s2;
create table t1 (id1 integer default nextval('s1'), id2 integer default nextval('s2'), id3 integer default nextval('s2'));

select sn.nspname as sequence_schema, s.relname as sequence_name, col.attname
from pg_class s
join pg_namespace sn on sn.oid = s.relnamespace
join pg_depend d on d.refobjid = s.oid and d.refclassid='pg_class'::regclass
join pg_attrdef ad on ad.oid = d.objid and d.classid = 'pg_attrdef'::regclass
join pg_attribute col on col.attrelid = ad.adrelid and col.attnum = ad.adnum
join pg_class tbl on tbl.oid = ad.adrelid
join pg_namespace n on n.oid = tbl.relnamespace
where s.relkind = 'S'
and d.deptype in ('a', 'n')
and n.nspname = 'public'
and tbl.relname = 't1'

Returns

sequence_schema | sequence_name | attname
----------------+---------------+--------
public | s1 | id1
public | s2 | id2
public | s2 | id3

Thomas