See Catalog:action & Catalog:privateAction below.
These functions support iterative catalog access, to divide catalog updates into chunks...
Also, they support retries to deal with contention in case another plugin task is already accessing the catalog.
-- private method:
function Catalog:_isAccessContention( qual )
local found = qual:find( "LrCatalog:with", 1, true ) or 0 -- return position or zero, instead of position or nil.
if found == 1 then -- problem reported by with-catalog-do method.
local found2 = qual:find( "already inside", 15, true )
if found2 == nil then
found2 = qual:find( "was blocked", 15, true ) -- Lr4b
end
if found2 then
-- problem is due to catalog access contention.
Debug.logn( 'catalog contention:', str:to( qual ) )
return true
else
return false
end
else
return false
end
end
-- private method:
function Catalog:_action( catFunc, tmo, name, func, ... )
local t = { ... }
local tries = math.max( math.ceil( tmo * 2 ), 1 )
local sts, msg
local function _func( context )
sts, msg = func( unpack( t ) )
end
local count = 10000000 -- ten million max, for sanity.
repeat
local s, other
if name then
s, other = LrTasks.pcall( catFunc, catalog, name, _func )
else
s, other = LrTasks.pcall( catFunc, catalog, _func )
end
if s then -- no error thrown
if sts then
return true -- all done.
elseif str:is( msg ) then
return false, "Unable to complete catalog update - " .. msg
else
-- continue
count = count - 1
end
else
if self:_isAccessContention( other ) then
tries = tries - 1
if tries == 0 then
return nil, "Unable to access catalog for " .. str:to( tmo ) .. " seconds."
else
LrTasks.sleep( math.random( .1, 1 ) ) -- sleep for half second, plus or minus.
end
else
return nil, "Catalog access function error: " .. str:to( other )
end
end
until count == 0
return nil, "Program failure"
end
--- Wrapper for named/undoable catalog:withWriteAccessDo method - divide to conquor func.
--
-- @param tmo (number) max seconds to get in.
-- @param name (string) undo title.
-- @param func (function) divided catalog writing function: returns sts, msg = true when done; false if to be continued; nil, error message if trouble.
-- @param ... (any) passed to func - often a table containing photo start index.
--
-- @usage example:<br>
-- local function catalogAction( t )<br>
-- if t.i > #photos then<br>
-- return true -- done, no errors (although should pre-check for photos to process).<br>
-- else<br>
-- local k = math.min( t.i + 1000, #photos )<br>
-- while ( t.i <= k ) do<br>
-- -- do something to photos[t.i]<br>
-- -- if trouble, return nil, msg.<br>
-- t.i = t.i + 1
-- end<br>
-- if t.i > #photos then<br>
-- return true -- done, no errors.<br>
-- else<br>
-- return false -- continue, no errors.<br>
-- end<br>
-- end<br>
-- end<br>
-- local sts, msg = cat:action( 10, "Test", catalogAction, { i=1 } )<br>
-- if sts then<br>
-- -- log successful message.<br>
-- else<br>
-- -- print error message...<br>
-- end<br>
--
function Catalog:action( tmo, name, func, ... )
return self:_action( catalog.withWriteAccessDo, tmo, name, func, ... )
end
--- Wrapper for un-named catalog:withPrivateWriteAccessDo method - divide to conquor func.
--
--
-- @param tmo (number) max seconds to get in.
-- @param func (function) divided catalog writing function: returns sts, msg = true when done; false if to be continued; nil, error message if trouble.
-- @param ... (any) passed to func.
--
function Catalog:privateAction( tmo, func, ... )
return self:_action( catalog.withPrivateWriteAccessDo, tmo, nil, func, ... ) -- no name.
end
Note: These functions were changed a bit after further testing and integration - consider them for example purposes only. The released version of these functions will be available shortly as part of the Elare Plugin Framework:
https://www.assembla.com/spaces/lrdevplugin/
PS - After some mods, the final version allows me to write code like this which I find convenient (still not released yet at assembla.com):
local coll
local s, m = cat:update( 10, "Assure Folder Collection", function( context, phase )
if phase == 1 then
coll = catalog:createCollection( folder:getName(), parent, true )
return false -- keep going.
elseif phase == 2 then
coll:removeAllPhotos()
return false -- keep going.
elseif phase == 3 then
coll:addPhotos( folder:getPhotos() )
return true -- done (same as returning nil).
else
app:error( "bad phase" )
end
end )
if s then
app:logVerbose( "Assured collection: ^1", coll:getName() )
return coll
else
return nil, m
end
or
local photos = catalog:getAllPhotos()
local s, m = cat:update( 10, "Update Photos", function( context, phase )
local i1 = (phase - 1) * 1000 + 1
local i2 = math.min( phase * 1000, #photos )
for i = i1, i2 do
local photo = photos[i]
-- do something with photo that writes catalog.
end
if i2 < #photos then
return false -- keep going
end
end )
if s then
app:logVerbose( "Photos updated..." )
return true
else
return false, m
end
