copy table (create table like) - not keeping auto incrementing primary key - sql

Question

I'm new to postgres (on 9.5) and I can't find this in the docs anywhere.
Basically create a table like this:
CREATE TABLE test (
id serial primary key,
field1 CHARACTER VARYING(50)
);
Then copy it:
create table test_copy (like test);
The table test has these columns:
COLUMN_NAME id field1
DATA_TYPE 4 12
TYPE_NAME serial varchar
COLUMN_SIZE 10 50
IS_NULLABLE NO YES
IS_AUTOINCREMENT YES NO
But test_copy has these:
COLUMN_NAME id field1
DATA_TYPE 4 12
TYPE_NAME int4 varchar
COLUMN_SIZE 10 50
IS_NULLABLE NO YES
IS_AUTOINCREMENT NO NO
Why am I losing serial and autoincrement? How can I make a copy of a table that preserves these?

Answer 1

This is because serial isn't really a datatype. It gets "expanded" to an integer + a sequence + a default value.
See the manual for details
To get the default definition you need to use create table test_copy (like test INCLUDING DEFAULTS).
However, that will then use the same sequence as the original table.
You can see the difference when you display the table definition in psql:
psql (9.5.3)
Type "help" for help.
postgres=> CREATE TABLE test (
postgres(> id serial primary key,
postgres(> field1 CHARACTER VARYING(50)
postgres(> );
CREATE TABLE
postgres=> create table test_copy_no_defaults (like test);
CREATE TABLE
postgres=> create table test_copy (like test including defaults);
CREATE TABLE
postgres=> \d test
Table "public.test"
Column | Type | Modifiers
--------+-----------------------+---------------------------------------------------
id | integer | not null default nextval('test_id_seq'::regclass)
field1 | character varying(50) |
Indexes:
"test_pkey" PRIMARY KEY, btree (id)
postgres=> \d test_copy
Table "public.test_copy"
Column | Type | Modifiers
--------+-----------------------+---------------------------------------------------
id | integer | not null default nextval('test_id_seq'::regclass)
field1 | character varying(50) |
postgres=> \d test_copy_no_defaults
Table "public.test_copy_no_defaults"
Column | Type | Modifiers
--------+-----------------------+-----------
id | integer | not null
field1 | character varying(50) |

Answer 2

you can try:
create table test_inh () inherits (test);
and then
alter table test_inh no inherit test;
should leave same sequence default value for you