Add Insert A Bunch Of Records With Generate Series as a postgres til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_1122 TILs and counting..._
+_1123 TILs and counting..._
 
 ---
 
@@ -572,6 +572,7 @@ _1122 TILs and counting..._
 - [Get The Size Of An Index](postgres/get-the-size-of-an-index.md)
 - [Getting A Slice Of An Array](postgres/getting-a-slice-of-an-array.md)
 - [Group By The Result Of A Function Call](postgres/group-by-the-result-of-a-function-call.md)
+- [Insert A Bunch Of Records With Generate Series](postgres/insert-a-bunch-of-records-with-generate-series.md)
 - [Insert Just The Defaults](postgres/insert-just-the-defaults.md)
 - [Install Postgres With uuid-ossp Using asdf](postgres/install-postgres-with-uuid-ossp-using-asdf.md)
 - [Integers In Postgres](postgres/integers-in-postgres.md)

postgres/insert-a-bunch-of-records-with-generate-series.md

@@ -0,0 +1,38 @@
+# Insert A Bunch Of Records With Generate Series
+
+Sometimes you want to quickly insert a bunch of fake (or real) data into a
+Postgres table. This is a great way to populate seed data or set up data
+scenarios for testing things out.
+
+For instance, I recently used the following query to generate a bunch of data
+in a `roles` table to test out a query performance issue.
+
+```sql
+> insert into roles (
+    name,
+    resource_id,
+    resource_type,
+    created_at,
+    updated_at
+  )
+  select
+    'organization_user',
+    g.id,
+    'Organization',
+    now(),
+    now()
+  from generate_series(1,54000) as g(id);
+```
+
+The key part is the [`generate_series()`
+function](https://www.postgresql.org/docs/current/functions-srf.html) which
+will produce a row for every value between the two arguments. In this case, it
+will generate `1`, `2`, `3`, etc. all the way up to `54000` -- so 54k rows in
+total.
+
+The query selects off that generated series with some static values and some
+timestamps to create sufficiently fake data that can be inserted into the
+specified columns of the `roles` table.
+
+This quickly inserts tens of thousands of records that I can now use to test
+out the performance of a SQL query.