如何将主键从整数转换为串行？

Question

In a Postgres 9.3 table I have an integer as primary key with automatic sequence to increment, but I have reached the maximum for integer . How to convert it from integer to serial ?
I tried:

ALTER TABLE my_table ALTER COLUMN id SET DATA TYPE bigint;

But the same does not work with the data type serial instead of bigint . Seems like I cannot convert to serial ?

Answer 1

serial is a pseudo data type, not an actual data type. It's an integer underneath with some additional DDL commands executed automatically:

1. Create a sequence (with matching name by default).
2. Set the column NOT NULL and the default to draw from that sequence.
3. Make the column "own" the sequence.

Details:

• Safely and cleanly rename tables that use serial primary key columns in Postgres?

A bigserial is the same, built around a bigint column. You want bigint , but you already achieved that. To transform an existing serial column into a bigserial (or smallserial ), all you need to do is to ALTER the data type of the column. Sequences are generally based on bigint , so the same sequence can be used for any integer type.

To "change" a bigint into a bigserial or an integer into a serial , you just have to do the rest by hand:

• Creating a PostgreSQL sequence to a field (which is not the ID of the record)

The actual data type is still integer / bigint . Some clients like pgAdmin will display the data type serial in the reverse engineered CREATE TABLE script, if all criteria for a serial are met.