select: fix traverse start key in case condition + after

A comparator that choosed a starting key for select from a condition
value and after always returned a smaller one. This led to an
unsymmetric behavior depending on the direction of a traverse. Plus
conditions didn't work correctly in all cases.

Author: oleg-jukovec

CHANGELOG.md

@@ -31,6 +31,27 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
     - [1, 477, 'Alexey', 'Adams', 20]
   ...
 
+* `crud.select()` filtration by a first condition if the condition is '>'
+  or '>=' and it's value > `after`.
+
+  Before this patch:
+
+  tarantool> crud.select('developers', {{'>=', 'id', 5}}, {first = 10, after = rows[2]}).rows
+  ---
+  - - [3, 2804, 'Pavel', 'Adams', 27]
+    - [4, 1161, 'Mikhail', 'Liston', 51]
+    - [5, 1172, 'Dmitry', 'Jacobi', 16]
+    - [6, 1064, 'Alexey', 'Sidorov', 31]
+  ...
+
+  After this patch:
+
+  tarantool> crud.select('developers', {{'>=', 'id', 5}}, {first = 10, after = rows[2]}).rows
+  ---
+    - [5, 1172, 'Dmitry', 'Jacobi', 16]
+    - [6, 1064, 'Alexey', 'Sidorov', 31]
+  ...
+
 ## [0.11.2] - 23-05-22
 
 ### Added

crud/select/executor.lua

@@ -42,9 +42,11 @@ end
 local generate_value
 
 if has_keydef then
-    generate_value = function(after_tuple, scan_value, index_parts)
+    generate_value = function(after_tuple, scan_value, index_parts, tarantool_iter)
+        local cmp_operator = select_comparators.get_cmp_operator(tarantool_iter)
         local key_def = keydef_lib.new(index_parts)
-        if key_def:compare_with_key(after_tuple, scan_value) < 0 then
+        local cmp = key_def:compare_with_key(after_tuple, scan_value)
+        if (cmp_operator == '<' and cmp < 0) or (cmp_operator == '>' and cmp > 0) then
             return key_def:extract_key(after_tuple)
         end
     end

test/integration/select_test.lua

@@ -273,6 +273,94 @@ pgroup.test_negative_first = function(g)
     t.assert_equals(objects, helpers.get_objects_by_idxs(customers, {6}))
 end
 
+pgroup.test_positive_first = function(g)
+    local customers = helpers.insert_objects(g, 'customers', {
+        {
+            id = 1, name = "Elizabeth", last_name = "Jackson",
+            age = 11, city = "New York",
+        }, {
+            id = 2, name = "Mary", last_name = "Brown",
+            age = 22, city = "Los Angeles",
+        }, {
+            id = 3, name = "David", last_name = "Smith",
+            age = 33, city = "Los Angeles",
+        }, {
+            id = 4, name = "William", last_name = "White",
+            age = 44, city = "Chicago",
+        }, {
+            id = 5, name = "Jack", last_name = "Sparrow",
+            age = 55, city = "London",
+        }, {
+            id = 6, name = "William", last_name = "Terner",
+            age = 66, city = "Oxford",
+        }, {
+            id = 7, name = "Elizabeth", last_name = "Swan",
+            age = 77, city = "Cambridge",
+        }, {
+            id = 8, name = "Hector", last_name = "Barbossa",
+            age = 88, city = "London",
+        },
+    })
+
+    table.sort(customers, function(obj1, obj2) return obj1.id < obj2.id end)
+
+    -- id >= 3
+    -- first 10 after 5
+    local conditions = {
+        {'>=', 'id', 3},
+    }
+    local first = 10
+    local after = crud_utils.flatten(customers[5], g.space_format)
+    local result, err = g.cluster.main_server.net_box:call(
+       'crud.select', {'customers', conditions, {first=first, 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, {6, 7, 8}))
+
+    -- id <= 3
+    -- first 10 after 5
+    local conditions = {
+        {'<=', 'id', 3},
+    }
+    local first = 10
+    local after = crud_utils.flatten(customers[5], g.space_format)
+    local result, err = g.cluster.main_server.net_box:call(
+       'crud.select', {'customers', conditions, {first=first, 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, 2, 1}))
+
+    -- id <= 6
+    -- first 10 after 5
+    local conditions = {
+        {'<=', 'id', 6},
+    }
+    local first = 10
+    local after = crud_utils.flatten(customers[5], g.space_format)
+    local result, err = g.cluster.main_server.net_box:call(
+       'crud.select', {'customers', conditions, {first=first, 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, {4, 3, 2, 1}))
+
+    -- id >= 6
+    -- first 10 after 2
+    local conditions = {
+        {'>=', 'id', 6},
+    }
+    local first = 10
+    local after = crud_utils.flatten(customers[2], g.space_format)
+    local result, err = g.cluster.main_server.net_box:call(
+       'crud.select', {'customers', conditions, {first=first, 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, {6, 7, 8}))
+end
+
 pgroup.test_negative_first_with_batch_size = function(g)
     local customers = helpers.insert_objects(g, 'customers', {
         {