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126 lines
3.1 KiB
Markdown
126 lines
3.1 KiB
Markdown
---
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title: "Simple Key-Value Store using Sqlite3"
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date: 2023-11-09T22:15:23-05:00
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draft: false
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tags: ["DB"]
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math: false
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medium_enabled: false
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---
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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.
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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.
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For our key-value store, we're going to use a table with two columns:
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- A key, which we'll call `name`. This will be a unique `TEXT` type that has to be set.
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- The value, which we'll call `value` (Creative, I know.) For our purposes, this will also be a `TEXT` type.
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The SQL to create this table is
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```sql
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CREATE TABLE config(
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name TEXT NOT NULL UNIQUE,
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value TEXT
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);
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```
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Let's say we want to get the value of the key `author`. This is a `SELECT` statement away:
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```sql
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SELECT value FROM config where name='author';
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```
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Now let's say that we want to insert a new key into the table.
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```sql
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INSERT INTO config(name, value) VALUES ('a', '1');
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```
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What about updating?
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```sql
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UPDATE config SET value='2' WHERE name='a';
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```
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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).
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```sql
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INSERT INTO config(name, value) VALUES ('a', '3') ON CONFLICT(name) DO UPDATE SET value=excluded.value;
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```
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Lastly if you want to export the entire key-value store as a CSV:
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```bash
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sqlite3 -header -csv data.db "SELECT * FROM config;"
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```
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This is nice and all, but it's inconvinient to type out all these SQL commands. Therefore, I wrote two little bash scripts.
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**`sqlite3_getkv`**
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```bash
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#!/bin/sh
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set -o errexit
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set -o nounset
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set -o pipefail
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show_usage() {
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echo "Usage: sqlite3_getkv [db_file] [key]"
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exit 1
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}
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# Check argument count
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if [ "$#" -ne 2 ]; then
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show_usage
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fi
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# Initalize database file is not already
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sqlite3 "$1" "CREATE TABLE IF NOT EXISTS config(name TEXT NOT NULL UNIQUE, value TEXT);"
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# Get value from key
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sqlite3 "$1" "SELECT value FROM CONFIG where name='$2';"
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```
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**`ssqlite3_setkv`**
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```bash
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#!/bin/sh
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set -o errexit
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set -o nounset
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set -o pipefail
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show_usage() {
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echo "Usage: sqlite3_setkv [db_file] [key] [value]"
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exit 1
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}
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# Check argument count
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if [ "$#" -ne 3 ]; then
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show_usage
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fi
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# Initalize database file is not already
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sqlite3 "$1" "CREATE TABLE IF NOT EXISTS config(name TEXT NOT NULL UNIQUE, value TEXT);"
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# Set key-value pair
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sqlite3 "$1" "INSERT INTO config(name, value) VALUES ('$2', '$3') ON CONFLICT(name) DO UPDATE SET value=excluded.value;"
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```
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**Example Usage:**
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```
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$ ./sqlite3_setkv.sh test.db a 4
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$ ./sqlite3_setkv.sh test.db c 5
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$ ./sqlite3_getkv.sh test.db a
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4
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$ ./sqlite3_setkv.sh test.db a 5
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$ ./sqlite3_getkv.sh test.db a
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5
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```
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[^1]: Somehow my idea of easier, simpler, and more maintainable is writing bash scripts.
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