MidoriDB

In-memory database written in C completely from scratch.

Features

• Dependency Minimalism: It relies solely on libc and libm in runtime, ensuring easy integration and reducing external dependencies
• Custom Implementation: Every component of MidoriDB has been crafted from the ground up - mostly because I wanted to learn about it really
• Small Footprint: approximately 200KB.

Build

On ubuntu:

apt install bison flex libfl-dev

# if you want to build tests
apt install libcunit1-dev

To build it, just run:

make

Running tests

make all
./build/tests/run_unit_tests

Linking shared-object with your executable

gcc  -L<root_repo>/build/               \
        -lmidoridb                      \
        -Wl,-rpath <root_repo>/build/	\
        -o your_code

Example

#include <engine/query.h>

int main(void) {
        struct database db = {0};
        struct query_output *output;
        
        if (database_open(&db) != MIDORIDB_OK)
                return -1;        

        output = query_execute(&db, "SELECT "
                                    "    id_a, COUNT(*) "
                                    "FROM "
                                    "    A INNER JOIN B "
                                    "    ON A.id_a = B.id_b "
                                    "GROUP BY "
                                    "    id_a;");        

        if (output->status != ST_OK_WITH_RESULTS)
                return -1;
        
        while (query_cur_step(&output->results) == MIDORIDB_ROW) {
                printf("id_a: %ld, count: %ld\n"
                        query_column_int64(&output->results, 0),
                        query_column_int64(&output->results, 1));
        }        
        
        query_free(output);
        database_close(&db);
        return 0;
}

Wishlist

To make sure I won't lose focus on what I want this database to be able to do, I decided to write a list of features that I want to implement in the short to medium term.

• In-memory
• Parser (CREATE, SELECT, INSERT, UPDATE, DELETE)
• Recursive JOINs (INNER - more to come)
• Recursive expressions (INSERT)
• Locking [Granularity -> Table-level]

References

These are all the references that helped me a lot during the development of MidoriDB

Books:

• https://www.amazon.com/flex-bison-Text-Processing-Tools/dp/0596155972
• https://www.amazon.com/Database-Internals-Deep-Distributed-Systems/dp/1492040347

Courses:

• https://www.youtube.com/watch?v=LWS8LEQAUVc&list=PLSE8ODhjZXjYzlLMbX3cR0sxWnRM7CLFn