clean all luakit sqlite3 databases

db_clean.lua

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-- :dbclean command to vacuum all open sqlite databases --
-- (C) 2011 Mason Larobina <mason.larobina@gmail.com>   --
----------------------------------------------------------

-- Note: this needs to be required in your config before any databases
-- are created (i.e. before the history and cookies libs)

require "coroutine"
require "lfs"

-- Table of all database objects
local all_dbs = setmetatable({}, { __mode = "kv" })

-- Watch for new sqlite3 database instances
sqlite3.add_signal("new", function (db)
    print("New db", db)
    all_dbs[db] = db
end)

local cmd = lousy.bind.cmd
add_cmds{
    -- Vacuum all dbs
    -- http://sqlite.org/lang_vacuum.html
    cmd("dbclean", function (w)
        function vacuum()
            local reaped, count = 0, 0
            -- Clone db list to prevent GC of items while iterating
            for _, db in pairs(lousy.util.table.clone(all_dbs)) do
                if db.open then
                    count = count + 1
                    local file = db.filename
                    local size = lfs.attributes(file).size
                    w:set_prompt(string.format("Re-constructing database: "
                        .. "%s (%.2fMB)", file, size / (1024 * 1024)))

                    -- Wait for GUI update (so that the prompt becomes visible)
                    -- and then start the vacuum.
                    coroutine.yield()
                    db:exec("VACUUM;")
                    reaped = reaped + (size - lfs.attributes(file).size)
                end
            end
            -- Print stats
            w:set_prompt(string.format("Vacuums complete, %.2fMB reclaimed "
                .. "over %d open databases.", reaped, count))
        end
        co = coroutine.create(vacuum)
        luakit.idle_add(function ()
            return coroutine.resume(co)
        end)
    end)
}