select: fix LE and after results when the condition value < after

LE with after has always been replaced by LT. The idea was to start
traverse not from the after value, but from a next value. The
micro-optimization allowed to fetch one less tuple per time.

But this caused the condition value to be skipped if the value is less
than the after value.

Author: oleg-jukovec

CHANGELOG.md

@@ -12,6 +12,24 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Changed
 
 ### Fixed
+* `crud.select()` if a condition is '<=' and it's value < `after`.
+
+  Before this patch:
+
+  tarantool> crud.select('developers', {{'<=', 'id', 3}}, {first = 10, after = rows[5]}).rows
+  ---
+  - - [2, 401, 'Sergey', 'Allred', 21]
+    - [1, 477, 'Alexey', 'Adams', 20]
+  ...
+
+  After this patch:
+
+  tarantool> crud.select('developers', {{'<=', 'id', 3}}, {first = 10, after = rows[5]}).rows
+  ---
+  - - [3, 2804, 'Pavel', 'Adams', 27]
+    - [2, 401, 'Sergey', 'Allred', 21]
+    - [1, 477, 'Alexey', 'Adams', 20]
+  ...
 
 ## [0.11.2] - 23-05-22
 

crud/compare/plan.lua

@@ -266,9 +266,7 @@ function plan.new(space, conditions, opts)
     -- Moreover, for correct pagination we change iterator
     -- to continue iterating in direct and reverse order.
     if scan_after_tuple ~= nil then
-        if scan_iter == box.index.LE then
-            scan_iter = box.index.LT
-        elseif scan_iter == box.index.EQ then
+        if scan_iter == box.index.EQ then
             scan_iter = box.index.GE
         elseif scan_iter == box.index.REQ then
             scan_iter = box.index.LT

test/integration/select_test.lua

@@ -592,6 +592,14 @@ pgroup.test_le_condition_with_index = function(g)
     t.assert_equals(err, nil)
     local objects = crud.unflatten_rows(result.rows, result.metadata)
     t.assert_equals(objects, helpers.get_objects_by_idxs(customers, {1})) -- in age order
+
+    -- after obj 2
+    local after = crud_utils.flatten(customers[2], g.space_format)
+    local result, err = g.cluster.main_server.net_box:call('crud.select', {'customers', conditions, {after=after}})
+
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(customers, {3, 1})) -- in age order
 end
 
 pgroup.test_lt_condition_with_index = function(g)

test/unit/select_plan_test.lua

@@ -254,7 +254,7 @@ g.test_first = function()
     t.assert_equals(plan.scan_value, {777}) -- after_tuple id
     t.assert_equals(plan.after_tuple, after_tuple)
     t.assert_equals(plan.scan_condition_num, nil)
-    t.assert_equals(plan.tarantool_iter, box.index.LT) -- inverted iterator
+    t.assert_equals(plan.tarantool_iter, box.index.LE) -- inverted iterator
     t.assert_equals(plan.total_tuples_count, 10)
     t.assert_equals(plan.sharding_key, nil)
     t.assert_equals(plan.field_names, nil)