Add Generate Modern Primary Key Columns as a Postgres TIL

postgres/generate-modern-primary-key-columns.md

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+# Generate Modern Primary Key Columns
+
+Chances are if you have looked at some examples, blog posts, or real-world
+instances of a `create table` statement, it defined the primary key with
+`serial` (or `bigserial`).
+
+```sql
+create table books (
+  id serial primary key,
+  title text not null,
+  author text not null,
+  created_at timestamptz not null default now(),
+  updated_at timestamptz not null default now()
+);
+```
+
+The `serial` syntax is everywhere, but for quite a while now it has not been
+the recommended way to define a primary key column for the `int` or `bigint`
+data types.
+
+The ["Don't Do This" page of the PostgreSQL
+wiki](https://wiki.postgresql.org/wiki/Don%27t_Do_This#Don.27t_use_serial) says
+"Don't use serial".
+
+> For new applications, identity columns should be used instead. The serial
+> types have some weird behaviors that make schema, dependency, and permission
+> management unnecessarily cumbersome.
+
+The modern way to define a primary key column for `int` or `bigint` is with a
+generated identity column.
+
+```sql
+create table books (
+  id int primary key generated always as identity,
+  title text not null,
+  author text not null,
+  created_at timestamptz not null default now(),
+  updated_at timestamptz not null default now()
+);
+```
+
+Check out the PostgreSQL docs for more about [identity
+columns](https://www.postgresql.org/docs/17/ddl-identity-columns.html).