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content/blog/simple-kv-store-sqlite.md

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+---
+title: "Simple Key-Value Store using Sqlite3"
+date: 2023-11-09T22:15:23-05:00
+draft: false
+tags: ["DB"]
+math: false
+medium_enabled: false
+---
+
+A lot of software nowadays are built for scale. You have to setup a Kubernetes cluster and deploy Redis for duplication in order to have a key-value store. Though for many small projects, I feel like it's overkill. 
+
+I'll show in this post, that we can have a nice simple[^1] key-value store using `sqlite3`. This gives us the benefit that we don't need to use system resources to run a daemon the entire time and only spin up a process when we need it.
+
+For our key-value store, we're going to use a table with two columns:
+
+- A key, which we'll call `name`. This will be a unique `TEXT` type that has to be set.
+- The value, which we'll call `value` (Creative, I know.) For our purposes, this will also be a `TEXT` type.
+
+The SQL to create this table is
+
+```sql
+CREATE TABLE config(
+    name TEXT NOT NULL UNIQUE,
+    value TEXT
+);
+```
+
+Let's say we want to get the value of the key `author`. This is a `SELECT` statement away:
+
+```sql
+SELECT value FROM config where name='author';
+```
+
+Now let's say that we want to insert a new key into the table.
+
+```sql
+INSERT INTO config(name, value) VALUES ('a', '1');
+```
+
+What about updating?
+
+```sql
+UPDATE config SET value='2' WHERE name='a';
+```
+
+The tricky part is if we want to insert if the key does not exist, and update if it does. To handle this we'll need to resolve the [conflict](https://www.sqlite.org/lang_conflict.html).
+
+```sql
+INSERT INTO config(name, value) VALUES ('a', '3') ON CONFLICT(name) DO UPDATE SET value=excluded.value;
+```
+
+Lastly if you want to export the entire key-value store as a CSV:
+
+```bash
+sqlite3 -header -csv data.db "SELECT * FROM config;"
+```
+
+This is nice and all, but it's inconvinient to type out all these SQL commands. Therefore, I wrote two little bash scripts.
+
+**`sqlite3_getkv`**
+
+```bash
+#!/bin/sh
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+show_usage() {
+    echo "Usage: sqlite3_getkv [db_file] [key]"
+    exit 1
+}
+
+# Check argument count
+if [ "$#" -ne 2 ]; then
+    show_usage
+fi
+
+# Initalize database file is not already
+sqlite3 "$1" "CREATE TABLE IF NOT EXISTS config(name TEXT NOT NULL UNIQUE, value TEXT);"
+
+# Get value from key
+sqlite3 "$1" "SELECT value FROM CONFIG where name='$2';"
+
+```
+
+**`ssqlite3_setkv`**
+
+```bash
+#!/bin/sh
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+show_usage() {
+    echo "Usage: sqlite3_setkv [db_file] [key] [value]"
+    exit 1
+}
+
+# Check argument count
+if [ "$#" -ne 3 ]; then
+    show_usage
+fi
+
+# Initalize database file is not already
+sqlite3 "$1" "CREATE TABLE IF NOT EXISTS config(name TEXT NOT NULL UNIQUE, value TEXT);"
+
+# Set key-value pair
+sqlite3 "$1" "INSERT INTO config(name, value) VALUES ('$2', '$3') ON CONFLICT(name) DO UPDATE SET value=excluded.value;"
+```
+
+**Example Usage:**
+
+```
+$ ./sqlite3_setkv.sh test.db a 4
+$ ./sqlite3_setkv.sh test.db c 5
+$ ./sqlite3_getkv.sh test.db a
+4
+$ ./sqlite3_setkv.sh test.db a 5
+$ ./sqlite3_getkv.sh test.db a
+5
+```
+
+[^1]: Somehow my idea of easier, simpler, and more maintainable is writing bash scripts.
+