<row>

<entry><literal><function>pg_get_serial_sequence(<parameter>table_name</parameter>, <parameter>column_name</parameter>)</function></literal></entry>

<entry><type>text</type></entry>

<entry>get name of the sequence that a <type>serial</type>, <type>smallserial</type> or <type>bigserial</type> column

uses</entry>

<entry>get name of the sequence that a serial or identity column uses</entry>

</row>

<row>

<entry><literal><function>pg_get_statisticsobjdef(<parameter>statobj_oid</parameter>)</function></literal></entry>

<para>

<function>pg_get_serial_sequence</function> returns the name of the

sequence associated with a column, or NULL if no sequence is associated

with the column. The first input parameter is a table name with

optional schema, and the second parameter is a column name. Because

the first parameter is potentially a schema and table, it is not treated

as a double-quoted identifier, meaning it is lower cased by default,

while the second parameter, being just a column name, is treated as

double-quoted and has its case preserved. The function returns a value

suitably formatted for passing to sequence functions (see <xref

linkend="functions-sequence">). This association can be modified or

removed with <command>ALTER SEQUENCE OWNED BY</>. (The function

probably should have been called

<function>pg_get_owned_sequence</function>; its current name reflects the fact

that it's typically used with <type>serial</> or <type>bigserial</>

columns.)

with the column. If the column is an identity column, the associated

sequence is the sequence internally created for the identity column. For

columns created using one of the serial types

(<type>serial</type>, <type>smallserial</type>, <type>bigserial</type>), it

is the sequence created for that serial column definition. In the latter

case, this association can be modified or removed with <command>ALTER

SEQUENCE OWNED BY</>. (The function probably should have been called

<function>pg_get_owned_sequence</function>; its current name reflects the

fact that it has typically been used with <type>serial</>

or <type>bigserial</> columns.) The first input parameter is a table name

with optional schema, and the second parameter is a column name. Because

the first parameter is potentially a schema and table, it is not treated as

a double-quoted identifier, meaning it is lower cased by default, while the

second parameter, being just a column name, is treated as double-quoted and

has its case preserved. The function returns a value suitably formatted

for passing to sequence functions

(see <xref linkend="functions-sequence">). A typical use is in reading the

current value of a sequence for an identity or serial column, for example:

<programlisting>

SELECT currval(pg_get_serial_sequence('sometable', 'id'));

</programlisting>

</para>

<para>

Form_pg_dependdeprec= (Form_pg_depend)GETSTRUCT(tup);

if (deprec->classid==RelationRelationId&&

(deprec->deptype==DEPENDENCY_AUTO||

deprec->deptype==DEPENDENCY_INTERNAL)&&

get_rel_relkind(deprec->objid)==RELKIND_SEQUENCE)

{

sequenceId=deprec->objid;

---------------

(0 rows)

SELECT pg_get_serial_sequence('itest1', 'a');

pg_get_serial_sequence

------------------------

public.itest1_a_seq

(1 row)

CREATE TABLE itest4 (a int, b text);

ALTER TABLE itest4 ALTER COLUMN a ADD GENERATED ALWAYS AS IDENTITY; -- error, requires NOT NULL

ERROR: column "a" of relation "itest4" must be declared NOT NULL before identity can be added

force | 100

(3 rows)

SELECT pg_get_serial_sequence('serialTest1', 'f2');

pg_get_serial_sequence

---------------------------

public.serialtest1_f2_seq

(1 row)

-- test smallserial / bigserial

CREATE TABLE serialTest2 (f1 text, f2 serial, f3 smallserial, f4 serial2,

f5 bigserial, f6 serial8);

SELECT sequence_nameFROMinformation_schema.sequencesWHERE sequence_nameLIKE'itest%';

SELECT pg_get_serial_sequence('itest1','a');

CREATETABLEitest4 (aint, btext);

ALTERTABLE itest4 ALTER COLUMN a ADD GENERATED ALWAYSAS IDENTITY;-- error, requires NOT NULL

ALTERTABLE itest4 ALTER COLUMN aSETNOT NULL;

SELECT*FROM serialTest1;

SELECT pg_get_serial_sequence('serialTest1','f2');

CREATETABLEserialTest2 (f1text, f2serial, f3 smallserial, f4 serial2,

f5bigserial, f6 serial8);