Data Store
LuaSettings
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DocSettings
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SQLite3
KOReader ships with the SQLite3 library, which is a great embedded database for desktop and mobile applications.
lua-ljsqlite3 is used to export SQLite3 C interfaces as LUA functions. Following is a quick example:
local SQ3 = require("lua-ljsqlite3/init") local conn = SQ3.open("/path/to/database.sqlite3") -- Execute SQL commands separated by the ';' character: conn:exec([[ -- time is in unit of seconds CREATE TABLE IF NOT EXISTS page_read_time(page INTEGER, time INTEGER); CREATE TABLE IF NOT EXISTS book_property(title TEXT, author TEXT, language TEXT); ]]) -- Prepared statements are supported, with this you can bind different values -- to the same statement. Let's set the read time for the first 10 pages in the -- book to 5 seconds local stmt = conn:prepare("INSERT INTO page_read_time VALUES(?, ?)") for i=1,10 do stmt:reset():bind(i, 5):step() end -- Now we can retrieve all read time stats for the first 10 pages: local results = conn:exec("SELECT * FROM page_read_time") -- Records are by column. -- Access to results via column numbers or names: assert(results[1] == results.page) assert(results[2] == results.time) -- Nested indexing corresponds to the record(row) number, access value for 4th page: assert(results[1][4] == 4) assert(results[2][4] == 5) -- access value for 2nd page: assert(results.page[2] == 2) assert(results.time[2] == 5) -- Convenience function returns multiple values for one record: local page, time = conn:rowexec("SELECT * FROM page_read_time WHERE page==3") print(page, time) --> 3 5 -- We can also use builtin aggregate functions to do simple analytic task local total_time = conn:rowexec("SELECT SUM(time) FROM page_read_time") print(total_time) --> 50 conn:close() -- Do not forget to close stmt after you are done
For more information on supported SQL queries, check out SQLite3's official documentation.