Add Manage Major Versions With Brew And Direnv as a Postgres TIL

postgres/manage-major-versions-with-brew-and-direnv.md

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+# Manage Major Versions With Brew and Direnv
+
+I can install multiple major versions of PostgreSQL to my machine with `brew`
+with commands like the following:
+
+```bash
+$ brew install postgresql@14
+$ brew install postgresql@16
+$ # ...
+```
+
+I can then start and stop specific Postgres server versions using the `brew
+services start/stop` commands. Let's say 14 is running, but I want to switch to 16.
+
+```bash
+$ brew services stop postgresql@14
+$ brew services start postgresql@16
+```
+
+Then I can use [`direnv`](https://direnv.net/) to manage the Postgres client
+(bin directory) that gets used for certain projects. This way when I run a
+command like `pg_dump` or `psql` it will use the one associated with a specific
+major version of Postgres.
+
+Assuming I already have `direnv` installed, I can add a `.envrc` to my project
+with the following line:
+
+```
+PATH_add /usr/local/opt/postgresql@16/bin
+```
+
+And then tell my system that the changes to this file are allowed to be sourced
+by `direnv`:
+
+```bash
+$ direnv allow .
+```
+
+That's it. Now I have PostgreSQL 16 (client and server) ready to use for my
+current project.