WingNews logo WingNews GitHub [2]

spanspan's comments

spanspan | 2 years ago | on: Show HN: I wrote a RDBMS (SQLite clone) from scratch in pure Python

I began using python as a way to "mock" out the overall design; intending to re-implement it in rust. The main reasoning for using python: was the ability to focus on "high-level" concepts and speed of tinkering. This implements a single process, single thread, single connection database- so performance and low-level concurrency control were not explicit goals or really optimized for. For those (real-live concerns) rust or C++ are much better; but also come with their set of complexities.

spanspan | 2 years ago | on: Show HN: I wrote a RDBMS (SQLite clone) from scratch in pure Python

Re: ACID guarantees

It doesn't have a notion of atomically batching multiple statements, i.e. transaction. But beyond that, it's a single file database, which can only have a single process (learndb instance) that is operating on the database (file). So you get consistency and isolation via being a single connection database. Durability, you get to the extent that the file system is durable. So it's somewhere on the ACIDity spectrum.

Re: Query planning/optimization

I haven't implemented this; but I've considered where the optimization could module sit: The parser spits out an AST. This or a derived intermediate representation could be optimized,i.e. the AST could be rewritten or nodes deleted, before the VM executes the AST.

spanspan | 2 years ago | on: Show HN: I wrote a RDBMS (SQLite clone) from scratch in pure Python

̶T̶h̶i̶s̶ ̶s̶t̶r̶i̶n̶g̶ ̶i̶s̶ ̶t̶h̶e̶ ̶g̶r̶a̶m̶m̶a̶r̶ ̶t̶h̶a̶t̶ ̶l̶a̶r̶k̶ ̶u̶s̶e̶s̶ ̶t̶o̶ ̶p̶a̶r̶s̶e̶ ̶t̶h̶e̶ ̶u̶s̶e̶r̶ ̶s̶u̶b̶m̶i̶t̶t̶e̶d̶ ̶s̶q̶l̶ ̶i̶n̶t̶o̶ ̶a̶n̶ ̶A̶S̶T̶.̶ ̶T̶h̶i̶s̶ ̶p̶a̶r̶s̶i̶n̶g̶ ̶i̶s̶ ̶f̶a̶r̶ ̶m̶o̶r̶e̶ ̶c̶o̶m̶p̶l̶e̶t̶e̶ ̶a̶n̶d̶ ̶r̶o̶b̶u̶s̶t̶ ̶t̶h̶a̶n̶ ̶w̶h̶a̶t̶ ̶d̶o̶i̶n̶g̶ ̶t̶h̶i̶s̶ ̶i̶n̶ ̶p̶u̶r̶e̶ ̶p̶y̶t̶h̶o̶n̶ ̶w̶o̶u̶l̶d̶ ̶a̶l̶l̶o̶w̶ ̶(̶w̶i̶t̶h̶o̶u̶t̶ ̶o̶f̶ ̶c̶o̶u̶r̶s̶e̶ ̶i̶m̶p̶l̶e̶m̶e̶n̶t̶i̶n̶g̶ ̶t̶h̶e̶ ̶e̶n̶t̶i̶r̶e̶ ̶l̶e̶x̶e̶r̶ ̶a̶n̶d̶ ̶p̶a̶r̶s̶e̶r̶ ̶t̶h̶a̶t̶ ̶l̶a̶r̶k̶ ̶i̶m̶p̶l̶e̶m̶e̶n̶t̶s̶)̶.̶

T̶h̶e̶r̶e̶ ̶m̶a̶y̶ ̶b̶e̶ ̶s̶o̶m̶e̶ ̶p̶o̶s̶t̶ ̶p̶a̶r̶s̶i̶n̶g̶ ̶v̶a̶l̶i̶d̶a̶t̶i̶o̶n̶ ̶t̶h̶a̶t̶ ̶c̶a̶n̶ ̶b̶e̶ ̶d̶o̶n̶e̶ ̶h̶e̶r̶e̶-̶ ̶b̶u̶t̶ ̶t̶h̶a̶t̶ ̶w̶o̶u̶l̶d̶ ̶b̶e̶ ̶s̶o̶m̶e̶t̶h̶i̶n̶g̶ ̶t̶h̶a̶t̶'̶s̶ ̶b̶e̶y̶o̶n̶d̶ ̶t̶h̶e̶ ̶d̶o̶m̶a̶i̶n̶ ̶o̶f̶ ̶t̶h̶e̶ ̶p̶a̶r̶s̶e̶r̶.̶

Edit: I see what you mean. I surveyed a bunch a parser generator libraries, and they also seemed to use a text based DSL- rather than DSL based on python structures. What you're describing would have made the grammar development more ergonomic and simple.

page 1