Add Use A Space To Exclude Command Fromm History as a Zsh 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://crafty-builder-6996.ck.page/e169c61186).
 
-_1477 TILs and counting..._
+_1479 TILs and counting..._
 
 ---
 
@@ -804,6 +804,7 @@ _1477 TILs and counting..._
 - [Pretty Printing JSONB Rows](postgres/pretty-printing-jsonb-rows.md)
 - [Prevent A Query From Running Too Long](postgres/prevent-a-query-from-running-too-long.md)
 - [Print The Query Buffer In psql](postgres/print-the-query-buffer-in-psql.md)
+- [Put Unique Constraint On Generated Column](postgres/put-unique-constraint-on-generated-column.md)
 - [Remove Not Null Constraint From A Column](postgres/remove-not-null-constraint-from-a-column.md)
 - [Renaming A Sequence](postgres/renaming-a-sequence.md)
 - [Renaming A Table](postgres/renaming-a-table.md)
@@ -1757,6 +1758,7 @@ _1477 TILs and counting..._
 
 - [Add To The Path Via Path Array](zsh/add-to-the-path-via-path-array.md)
 - [Link A Scalar To An Array](zsh/link-a-scalar-to-an-array.md)
+- [Use A Space To Exclude Command From History](zsh/use-a-space-to-exclude-command-from-history.md)
 
 ## Usage
 

postgres/put-unique-constraint-on-generated-column.md

@@ -0,0 +1,46 @@
+# Put Unique Constraint On Generated Column
+
+You cannot apply a _unique constraint_ to an expression over a column, e.g.
+`lower(email)`. You can, however, create a [generated
+column](https://www.postgresql.org/docs/current/ddl-generated-columns.html) for
+that expression and then apply the unique constraint to that generated column.
+
+Here is what that could look like:
+
+```sql
+> create table users (
+    id integer generated always as identity primary key,
+    name text not null,
+    email text not null,
+    email_lower text generated always as (lower(email)) stored,
+    unique ( email_lower )
+);
+
+> \d users
++-------------+---------+-----------------------------------------------------------------+
+| Column      | Type    | Modifiers                                                       |
+|-------------+---------+-----------------------------------------------------------------|
+| id          | integer |  not null generated always as identity                          |
+| name        | text    |  not null                                                       |
+| email       | text    |  not null                                                       |
+| email_lower | text    |  default lower(email) generated always as (lower(email)) stored |
++-------------+---------+-----------------------------------------------------------------+
+Indexes:
+    "users_pkey" PRIMARY KEY, btree (id)
+    "users_email_lower_key" UNIQUE CONSTRAINT, btree (email_lower)
+```
+
+And then an demonstration of violating that constraint:
+
+```sql
+
+> insert into users (name, email) values ('Bob', 'bob@email.com');
+INSERT 0 1
+
+> insert into users (name, email) values ('Bobby', 'BOB@email.com');
+duplicate key value violates unique constraint "users_email_lower_key"
+DETAIL:  Key (email_lower)=(bob@email.com) already exists.
+```
+
+The main tradeoff here is that you are doubling the amount of storage you need
+for that column. Unless it is a massive table, that is likely not an issue.

zsh/use-a-space-to-exclude-command-from-history.md

@@ -0,0 +1,37 @@
+# Use A Space To Exclude Command From History
+
+When using a shell like `zsh`, you get the benefit of it keeping track of the
+history of the commands you've entered into the shell. This means you can
+quickly traverse pack to a previous command that you want to run again. It also
+means [a tool like `fzf` can hook into your history
+file](https://github.com/junegunn/fzf?tab=readme-ov-file#key-bindings-for-command-line)
+so that you can fuzzy-search for a command you may have executed weeks ago.
+
+The history is stored on your machine in a plaintext file. Not every command
+should be stored in a plaintext file. For instance, you don't want `zsh` to
+persist a command that includes a password.
+
+With the `histignorespace` option enabled in `zsh`, we can put a leading space
+in front of our command and it will be excluded from the history file.
+
+Try it yourself:
+
+```bash
+$ echo 'this command will be remembered'
+this command will be remembered
+
+$  echo 'this command will be forgotten'
+this command will be forgotten
+```
+
+Notice the leading space in the second command. Trying pressing your _up_ arrow
+and notice only that first `echo` is remembered.
+
+Make sure `histignorespace` is included in the list when you run `setopt`. If
+it isn't, then add it:
+
+```bash
+$ setopt histignorespace
+```
+
+[source](https://stackoverflow.com/questions/8473121/execute-a-command-without-keeping-it-in-history/49643320#49643320)