smalldb's Introduction

SmallDB

A very simple database made with pure C++

Types

Double
Long
String (with max string length)
Datetime (no timezone)

Operations

insertRow()
find()
readDouble(), writeDouble()
readLong(), writeLong()
readString(), writeString()
readDatetime(), writeDatetime()
delete()

Architecture

The general arch is expressed in architecture.txt.

File layout

    |----------------|--------|-------|-------|-------|-------|-------|-   -|
    | number of rows | header | row 0 | row 1 | row 2 | row 3 | row 4 | ... |
    |----------------|--------|-------|-------|-------|-------|-------|-   -|

  Header:
    |---------------|------|-------------|------|-------------|-   -|------------|
    | header length | name | type letter | name | type letter | ... | row length |
    |---------------|------|-------------|------|-------------|-   -|------------|

    * name is std::string_view::c_str() with unicode support

    type letter:
      |-----|-----------------|     |-----|     |-----|     |-----|
      | 'S' | max size column | or  | 'D' | or  | 'L' | or  | 'T' |
      |-----|-----------------|     |-----|     |-----|     |-----|

      * type letter is the id letter for Datatype
      * max size column is the max size of the column in bytes, it is only used for String

  Row:
    |----------|----------|----------|-   -|
    | column 0 | column 1 | column 2 | ... |
    |----------|----------|----------|-   -|

    * row has predefined length according to each type for Double, Long and Datetime
    * if there is a string_view in the row, there will be length information in header

  Serialization for Datetime:
    |------|-------|-----|------|--------|--------|
    | year | month | day | hour | minute | second |
    |------|-------|-----|------|--------|--------|
 
    year, month, day, hour, minute, second are saved as uint32_t

  Serialization for string:
    |-          -|-       -|
    | characters | padding |
    |-          -|-       -|

    * pad with 0 until assigned string size is filled (for row skipping conveniences)
 
  * All lengths are uint32_t