Start key and iterator type

Added the ability from where to start the iterator
and the type of the iterator itself. Start key can
be set as a function (dynamic parameter) or just a
static value. The type of the iterator can be specified
either with the box.index.* constant,
or with the name for example, 'EQ' or box.index.EQ

Needed for: #50

README.md

@@ -43,6 +43,12 @@ Run a scheduled task to check and process (expire) tuples in a given space.
     * `index` - Name or id of the index to iterate on. If omitted, will use the primary index.
      If there's no index with this name, will throw an error.
      Supported index types are TREE and HASH, using other types will result in an error.
+    * `iterator_type` - Type of the iterator to use, as string or box.index constant, for example, "EQ" or box.index.EQ.
+     Default is box.index.ALL.
+     See https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_index/pairs/.
+    * `start_key` - Start iterating from the tuple with this index value. If the iterator is "EQ", iterate over tuples with this index value.
+     The index value may be a single value, if the index consists of one field, a tuple with the index key parts, or a function which returns such value.
+     If omitted or nil, all tuples will be checked.
     * `tuples_per_iteration` - Number of tuples to check in one batch (iteration). Default is 1024.
     * `on_full_scan_start` - Function to call before starting a tuple scan.
     * `on_full_scan_complete` - Function to call after completing a full scan.

expirationd.lua

@@ -46,6 +46,10 @@ local constants = {
     default_vinyl_assumed_space_len_factor = 2,
     -- default function on full scan
     default_on_full_scan = function() end,
+    -- default function for start_key
+    start_key = function() return nil end,
+    -- default iterating over the loop will go in ascending index
+    iterator_type = "ALL",
 }
 
 -- ========================================================================= --
@@ -93,7 +97,7 @@ local function default_do_worker_iteration(task)
     local space_len = task.vinyl_assumed_space_len
     local checked_tuples_count = 0
     local vinyl_checked_tuples_count = 0
-    for _, tuple in task.index:pairs(nil, {iterator = box.index.ALL}) do
+    for _, tuple in task.index:pairs(task.start_key(), {iterator = task.iterator_type}) do
         checked_tuples_count = checked_tuples_count + 1
         vinyl_checked_tuples_count = vinyl_checked_tuples_count + 1
         expiration_process(task, tuple)
@@ -232,6 +236,8 @@ local function create_task(name)
         on_full_scan_success           = constants.default_on_full_scan,
         on_full_scan_start             = constants.default_on_full_scan,
         on_full_scan_complete          = constants.default_on_full_scan,
+        start_key                      = constants.start_key,
+        iterator_type                  = constants.iterator_type,
     }, { __index = Task_methods })
     return task
 end
@@ -274,13 +280,21 @@ end
 --     * index                 -- Name or id of the index to iterate on; if omitted, will use the primary index;
 --                                if there's no index with this name, will throw an error.
 --                                supported index types are TREE and HASH, using other types will result in an error.
+--     * iterator_type         -- Type of the iterator to use, as string or box.index constant,
+--                                for example, 'EQ' or box.index.EQ; default is box.index.ALL;
+--                                see https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_index/pairs/.
+--     * start_key             -- Start iterating from the tuple with this index value;
+--                                or when iterator is 'EQ', iterate over tuples with this index value;
+--                                must be a value of the same data type as the index field or fields,
+--                                or a function which returns such value;
+--                                if omitted or nil, all tuples will be checked.
+--     * tuples_per_iteration  -- Number of tuples to check in one batch (iteration); default is 1024.
 --     * on_full_scan_start    -- Function to call before starting a full scan iteration.
 --     * on_full_scan_complete -- Function to call after completing a full scan iteration.
 --     * on_full_scan_success  -- Function to call after successfully completing a full scan iteration.
 --     * on_full_scan_error    -- Function to call after terminating a full scan due to an error.
 --     * args                  -- Passed to is_tuple_expired and
 --                                process_expired_tuple() as additional context.
---     * tuples_per_iteration  -- Number of tuples to check in one batch (iteration); default is 1024.
 --     * full_scan_time        -- Time required for a full index scan (in seconds).
 --     * iteration_delay       -- Max sleep time between iterations (in seconds).
 --     * full_scan_delay       -- Sleep time between full scans (in seconds).
@@ -344,6 +358,23 @@ local function expirationd_run_task(name, space_id, is_tuple_expired, options)
     end
     task.index = expire_index
 
+    -- check iterator_type
+    if options.iterator_type ~= nil then
+        task.iterator_type = options.iterator_type
+    end
+
+    -- check start_key
+    if options.start_key ~= nil or options.start_key == box.NULL then
+        if type(options.start_key) == "function" then
+            task.start_key = function() return options.start_key() end
+        else
+            task.start_key = function() return options.start_key end
+        end
+    end
+
+    -- check valid of iterator_type and start key
+    task.index:pairs( task.start_key(), { iterator = task.iterator_type })
+
     -- check expire and process after expiration handler's arguments
     task.args = options.args