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Show HN: GoSQL – A query engine in 319 LoC

by archiewood on 10/7/24, 12:39 PM with 9 comments

I've always been curious about how SQL engines actually work.

So I built a minimum viable SQL engine in Go.

- Supports CSV files as tables

- Supports SELECT, FROM, WHERE, LIMIT

It's very simple:

1. Parses query string

2. Converts it into an AST representation

3. Executes the query against the CSV

4. Returns the results

  • by stevekemp on 10/7/24, 5:03 PM

    Nice job.

    You can see this post for the start of a guide in implementing something very similar "Writing a SQL database from scratch in Go":

    https://notes.eatonphil.com/database-basics.html

    (Use the tag "sql" to find the later parts. Sadly not linked directly from that first one.)

  • by iamcreasy on 10/7/24, 5:44 PM

    Nice. I also wanted to know the details behind database engine and ACID compliance. So, decided to follow Database Design and Implementation by Edward Sciore, and re-implemented the database in Python: https://github.com/quazi-irfan/pySimpleDB

    This db treats file as raw disk and reads and writes in blocks. In the book, your step 3 and 4 will be a start of a transaction that uses recovery manager to log changes introduced by the query, and buffer manager to page in and out file blocks in memory. This book uses serializable isolation, so if buffer pool is full and can't page in new block or if another transactions are writing to that same block - the newer transaction will be rolled back after a brief wait.

  • by lainga on 10/7/24, 4:57 PM

  • by zh2408 on 10/7/24, 7:36 PM

    Feel like you can achieve something similar in duckdb? duckdb allows you to query local csv, parquet, and even remote ones?

  • by coredog64 on 10/7/24, 3:41 PM

    This is very handy given the recent de-emphasizing of S3 Select by AWS.

  • by ddmf on 10/8/24, 7:50 AM

    Nice one, thanks, I'll have a look through this.