SQLiteKV

SQLiteKV is a simple, single-file key-value store based on SQLite 3.

Why?

I wanted to have an OS and language independent single-file key-value database. By language independent, I mean at least the languages I use, i.e. Python and Go. After using a bit GDBM, it appears that it's not well supported by Go, and has some issue with the Anaconda environment. SQLite was the only engine to be equally well supported everywhere.

How?

The database has two tables.

keys that obviously contains the keys, and a foreign key to the corresponding value.
vals that only contains the values.

The key column of the keys table is indexed, which guarantees a fast finding, while slowing down the insertions. Having the keys and the values in separated tables guarantees the database to not be too big if there are far more keys than values, while complicating a bit the queries (and maybe slowing down a bit the value retrieving).

Naming the tables always like this allows to make the store language-independent.

Then, we follow the KISS philosophy: one file by programming language with the same three functions.

get to retrieve an a value from a key.
put to add a key-value association.
del to remove a key-value association.

However, this do not prevent from adding some language specific code to make the interface more idiomatic.

Schema

The keys table:

CREATE TABLE keys(
  key TEXT UNIQUE NOT NULL,
  valueID INTEGER NOT NULL,
  FOREIGN KEY(valueID) REFERENCES vals(ID))

The vals table:

CREATE TABLE vals(
  ID INTEGER PRIMARY KEY ASC,
  value TEXT UNIQUE NOT NULL)

The keys index:

CREATE UNIQUE INDEX idx_keys ON keys(key);

Simple Query

To retrieve the value associated with the key plop:

SELECT keys.key, vals.value FROM keys
INNER JOIN vals ON vals.ID=keys.valueID
WHERE keys.key='plop'

Licence