sqlite-fastrand by asg017

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A SQLite extension for quickly generating random numbers, booleans, characters, and blobs. Not cryptographically secure. Based on sqlite-loadable-rs and the fastrand crate.`

According to my local benchmarks, fastrand_int64() is about 2.6x faster than SQLite's random(), and fastrand_blob() is about 1.6x faster than randomblob(). sqlite-fastrand also offers a more ergonomic API with custom ranges, seeds, and boolean/character support. However, it yields psuedo-random results and isn't "truly" random.

If your company or organization finds this library useful, consider supporting my work!


.load ./fastrand0
select fastrand_int(); -- 556823563
select fastrand_int(); -- 363294620
select fastrand_int(); -- -320463573

Set a seed for the underlying random number generator, for deterministic values.

select fastrand_seed_set(1234);
select fastrand_int(); -- -2058591105
select fastrand_int(); -- -211244717
select fastrand_int(); -- -1772832958

select fastrand_seed_set(1234);
select fastrand_int(); -- -2058591105
select fastrand_int(); -- -211244717
select fastrand_int(); -- -1772832958

Include start and end (exclusive) parameters to generate random numbers within a range.

select fastrand_int(0, 10); -- 0
select fastrand_int(0, 10); -- 9
select fastrand_int(0, 10); -- 6

Generate random digits, lowercase/uppercase/alphabetic/alphanumeric characters.

select fastrand_alphabetic(); -- 's'
select fastrand_alphanumeric(); -- '2'
select fastrand_char(); -- '񠞼'
select fastrand_lowercase(); -- 'g'
select fastrand_uppercase();-- 'M'

select fastrand_digit(16); -- 'c'

Generate a random float between 0 and 1.

select fastrand_double(); -- 0.740834390248454
select fastrand_double(); -- 0.46936608707793

Differences from random() and randomblob()

The builtin random() and randomblob() are powerful tools that already exist in SQLite standard library, but they can be confusing at times.

For example, the random() function returns "... a pseudo-random integer between -9223372036854775808 and +9223372036854775807", which are the minimum and maximum values of a 64 bit signed integer.

select random(); -- 8247412491507365610
select random(); -- 8124278049726255864

This may work fine in your use-case, but typically I want a more constrained random number, like any number between 0-100. This can technically be done with random() if you use abs() and the modulus % operator, but it gets awkward:

select abs(random()) % 100; -- 96
select abs(random()) % 100; -- 41

The fastrand_int64() function works the same as random() but offers an optional start and end parameters to specify a range in which the random number should be generated in.

select fastrand_int64(); -- 5216671854996406003
select fastrand_int64(0, 100); -- 19


The randomblob(N) function return an N-byte blob containing pseudo-random bytes. If N is less than 1 then a 1-byte random blob is returned.

select hex(randomblob(16)); -- '4E7EFDB9E687EED4F376359986CB695E'
select hex(randomblob(16)); -- 'F6CFF9249E3BD8755E10D6BB3CA81C66'

The fastrand_blob(N) function acts in the same way.

select hex(fastrand_blob(16)); -- 'D86FF5409D3FAD7DBE707580C7E7DE14'
select hex(fastrand_blob(16)); -- 'AB72BFE9480197F487933E8071072D4A'


Language Install
Python pip install sqlite-fastrand PyPI
Datasette datasette install datasette-sqlite-fastrand Datasette
Node.js npm install sqlite-fastrand npm
Deno deno.land/x/sqlite_fastrand deno.land/x release
Ruby gem install sqlite-fastrand Gem
Github Release GitHub tag (latest SemVer pre-release)
Rust cargo add sqlite-fastrand Crates.io

The Releases page contains pre-built binaries for Linux x86_64, MacOS, and Windows.

As a loadable extension

If you want to use sqlite-fastrand as a Runtime-loadable extension, Download the fastrand0.dylib (for MacOS), fastrand0.so (Linux), or fastrand0.dll (Windows) file from a release and load it into your SQLite environment.

Note: The 0 in the filename (fastrand0.dylib/ fastrand0.so/fastrand0.dll) denotes the major version of sqlite-fastrand. Currently sqlite-fastrand is pre v1, so expect breaking changes in future versions.

For example, if you are using the SQLite CLI, you can load the library like so:

.load ./fastrand0
select fastrand_version();
-- v0.1.0

Or in Python, using the builtin sqlite3 module:

import sqlite3
con = sqlite3.connect(":memory:")
print(con.execute("select fastrand_version()").fetchone())
# ('v0.1.0',)

Or in Node.js using better-sqlite3:

const Database = require("better-sqlite3");
const db = new Database(":memory:");
console.log(db.prepare("select fastrand_version()").get());
// { 'fastrand_version()': 'v0.1.0' }

Or with Datasette:

datasette data.db --load-extension ./fastrand0


I (Alex 👋🏼) spent a lot of time and energy on this project and many other open source projects. If your company or organization uses this library (or you're feeling generous), then please consider supporting my work, or share this project with a friend!

See also