db

A simple proof-of-concept database that I worked on to practice using C++. Not for use in serious projects.

Currently, insert and select functions on tables work, as well as basic math, e.g. 2*(2+2) returns 8

Usage

Run cmake-build-debug-visual-studio/main.exe and place it in the same folder as the .dll files, which creates a local server on port 9000 which listens to post requests.
Use some software, such as Postman, to make a post request to the server with the body containing an array with the query, such as ["testDb.testTable.insert(\"Index1\", 3)"] (note the escaped quotes). This is done to provide flexibility in the future.

Language:

IdComponent

These are components which can have child components, which can be accessed with .
The Database and Table classes inherit from IdComponent class.
There are a few global variables, such as testDb, which is an instance of a database.
Each database has children tables, (testTable for the default testDb).

Each table has built-in functions (currently select(key) and insert(key, value))

ArrayComponent

Extends IdComponent to have some array functionality (currently there is not much difference)

NullComponent

A null value

NumberComponent

A number (a double) value

StringComponent

A string value

Underlying formats of data:

Structure of the database

There are two files: .pm and .sm .pm is a primary map file. When a key is looked up, its value is hashed and used to assign the index in the secondary map to the buckets in the primary map. Because it uses a principle similar to hashmaps, its complexity is O(1)

.sm is a secondary map file. A primary map entry points to a chosen location in the secondary map. Then, a linked list is used to find the correct value. It also has a complexity of O(1) because it is a pointer, except for the cases where the linked list is used.

Secondary map entry

length | nextObject | KeyLength | Key | Value

length - length of the whole field
nextObject - a pointer to the next object in the map with the same assigned bucket. This is used to prevent hash collisions by creating a linked list of entries.
KeyLength - length of the key in bytes Key - the key component (serialised) Value - the value component (serialised)

Serialised components

typeByte | serialisedValue

typeByte - a byte encodes the type of data stored in a cell, e.g. the byte 0x10 corresponds to a StringComponent. This is used to choose the correct method to decode the serialised data serialisedValue - the component that was converted to a series of bytes.