163 lines
3.7 KiB
Markdown
163 lines
3.7 KiB
Markdown
FlatDB
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===========
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FlatDB is a lua library that implements a serverless, zero-configuration, NoSQL database engine.<br>
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It provides a key-value storage system using plain Lua tables.
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When To Use FlatDB
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===========
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When you want to use SQLite to store data, just take a glance at FlatDB.<br>
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When Lua acts in your program as the major language or the embedded scripting language, just try using FlatDB.
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Concept
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==========
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| FlatDB | Disk | Lua |
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|:--------------:|:-------------:|:--------------:|
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| Database | Directory | Table |
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| Page | File | Table |
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| Key-value pair | File content | Key-value pair |
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Keys and values can be all Lua types except coroutines, userdata, cdata and C functions.
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Usage
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==========
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Copy *flatdb.lua* file to your project or where your lua libraries stored.<br>
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Then write this in any Lua file where you want to use it:
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```lua
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local flatdb = require 'flatdb'
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```
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1. Bind a directory as a database
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```lua
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local db = flatdb('./db')
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```
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2. Open or create a page
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```lua
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if not db.page then
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db.page = {}
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end
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```
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3. Store key-value items
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```lua
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db.page.key = 'value'
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-- equivalent to db.page['key'] = 'value'
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```
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4. Retrieve items
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```lua
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print(db.page.key) -- prints 'value'
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```
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5. Save to file
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```lua
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db:save()
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-- 'page' will be saved to './db/page'
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```
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More usage can be found in the *cli.lua*(a Redis-like command line interface example using FlatDB).
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Quick Look
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==========
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```lua
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-- This is an logging system example using FlatDB
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local flatdb = require("flatdb")
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local logger = flatdb("./log")
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local count = 0
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local function common_log(logger, level, message)
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local today = os.date("%Y-%m-%d")
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if logger[today] == nil then logger[today] = {} end
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if logger[today][level] == nil then logger[today][level] = {} end
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table.insert(logger[today][level], {
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timestamp = os.time(),
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level = level,
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message = message
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})
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count = (count+1)%10
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if count == 0 then
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logger:save()
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end
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end
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local levels = {"debug", "info", "warn", "error", "fatal"}
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for _, level in ipairs(levels) do
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flatdb.hack[level] = function(logger, msg)
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common_log(logger, level, msg)
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end
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end
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flatdb.hack.find = function(logger, level, date)
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if logger[date or os.date("%Y-%m-%d")] then
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return logger[date or os.date("%Y-%m-%d")][level]
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end
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end
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for i = 1, 10 do
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logger:debug("This is a debug message.")
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logger:info("This is an info message.")
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logger:warn("This is a warn message.")
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logger:error("This is an error message.")
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logger:fatal("This is a fatal message.")
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end
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local pp = require("pp")
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pp(logger:find("error"))
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```
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API
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==========
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- **Functions**
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- **flatdb(dir) --> db**
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Bind a directory as a database, returns nil if 'dir' doesn't exists. Otherwise, it returns a 'db' obeject.
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- **db:save([page])**
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Save all pages or the given page(if specified) contained in db to file. The 'page' argument is a string, the page's name.
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- **Tables**
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- **flatdb**
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When a db is loaded, there is two relations below:
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*flatdb[dir] --> db*
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*flatdb[db] --> dir*
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- **flatdb.hack**
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The 'hack' table contains db's methods. There is only one method 'save(db, page)' in it by default.
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It is usually used to extend db methods.
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Dependencies
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=======
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- [pp](https://github.com/luapower/pp)
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- [lfs](http://keplerproject.github.io/luafilesystem/)
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All above libraries can be found in [LuaPower](https://luapower.com/).
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License
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=======
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FlatDB is distributed under the MIT license.
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