Fix pagination + multipart indexes (#177)

Fixed invalid results for pagination queries when filtering on
a parts of a composite index. Now, instead of "scrolling" 
to the desired tuple (during pagination) using the 
``scroll_to_after_tuple`` function, we change the iterators 
(``EQ`` -> ``GE``, ``REQ`` -> ``LT``) to use them in 
``index:pairs`` function, together with a combination with 
additional filtration. Closes #170

Author: mRrvz

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Fixed
+
+* Invalid results for pagination queries when filtering on
+  a part of a composite index
+
 ### Added
 
 * Added jsonpath indexes support for queries

crud/select/plan.lua

@@ -182,6 +182,16 @@ function select_plan.new(space, conditions, opts)
         return nil, err
     end
 
+    -- Since we use pagination we should continue iteration since after tuple.
+    -- Such iterator could be run only with index:pairs(key(after_tuple), 'GT/LT').
+    -- To preserve original condition we should manually inject it in `filter_conditions`
+    -- See function `parse` in crud/select/filters.lua file for details.
+    if scan_after_tuple ~= nil then
+        if scan_iter == box.index.REQ or scan_iter == box.index.EQ then
+            table.insert(conditions, conditions[scan_condition_num])
+        end
+    end
+
     if opts.first ~= nil then
         total_tuples_count = math.abs(opts.first)
 
@@ -204,6 +214,18 @@ function select_plan.new(space, conditions, opts)
         end
     end
 
+    -- 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
+            scan_iter = box.index.GE
+        elseif scan_iter == box.index.REQ then
+            scan_iter = box.index.LT
+        end
+    end
+
     local sharding_index = primary_index -- XXX: only sharding by primary key is supported
 
     -- get sharding key value

test/integration/select_test.lua

@@ -898,16 +898,53 @@ pgroup:add('test_multipart_primary_index', function(g)
     })
 
     local conditions = {{'=', 'primary', 0}}
-    local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions})
+    local result_0, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions})
     t.assert_equals(err, nil)
-    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    local objects = crud.unflatten_rows(result_0.rows, result_0.metadata)
     t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {1, 2, 3}))
 
+    local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions,
+                                                                          {after = result_0.rows[1]}})
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {2, 3}))
+
+    local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions,
+                                                                          {after = result_0.rows[3], first = -2}})
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {1, 2}))
+
+    local new_conditions = {{'=', 'y', 1}, {'=', 'primary', 0}}
+    local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', new_conditions,
+                                                                          {after = result_0.rows[3], first = -2}})
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {2}))
+
     local conditions = {{'=', 'primary', {0, 2}}}
     local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions})
     t.assert_equals(err, nil)
     local objects = crud.unflatten_rows(result.rows, result.metadata)
     t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {3}))
+
+    local conditions_ge = {{'>=', 'primary', 0}}
+    local result_ge_0, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions_ge})
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result_ge_0.rows, result_ge_0.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {1, 2, 3, 4, 5}))
+
+    local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions_ge,
+                                                                          {after = result_ge_0.rows[1]}})
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {2, 3, 4, 5}))
+
+    local result, err = g.cluster.main_server.net_box:call('crud.select', {'coord', conditions_ge,
+                                                                          {after = result_ge_0.rows[3], first = -3}})
+    t.assert_equals(err, nil)
+    local objects = crud.unflatten_rows(result.rows, result.metadata)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(coords, {1, 2}))
 end)
 
 pgroup:add('test_select_partial_result_bad_input', function(g)
@@ -1424,8 +1461,6 @@ pgroup:add('test_jsonpath_index_field_pagination', function(g)
     local objects = crud.unflatten_rows(result.rows, result.metadata)
     t.assert_equals(objects, helpers.get_objects_by_idxs(cars, {1, 2}))
 
---[==[
-    -- Uncomment after https://github.com/tarantool/crud/issues/170
     -- Pagination (secondary index - 1 field)
     local result, err = g.cluster.main_server.net_box:call('crud.select',
         {'cars', {{'==', 'data_index', 'Yellow'}}, {first = 2}})
@@ -1445,7 +1480,6 @@ pgroup:add('test_jsonpath_index_field_pagination', function(g)
     local result, err = g.cluster.main_server.net_box:call('crud.select',
         {'cars', {{'==', 'data_index', 'Yellow'}}, {first = -2, after = result.rows[1]}})
     t.assert_equals(err, nil)
-]==]
 
     local objects = crud.unflatten_rows(result.rows, result.metadata)
     t.assert_equals(objects, helpers.get_objects_by_idxs(cars, {1, 2}))

test/unit/select_plan_test.lua

@@ -256,7 +256,29 @@ 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.LE) -- inverted iterator
+    t.assert_equals(plan.tarantool_iter, box.index.LT) -- inverted iterator
+    t.assert_equals(plan.total_tuples_count, 10)
+    t.assert_equals(plan.sharding_key, nil)
+    t.assert_equals(plan.field_names, nil)
+
+    -- select by primary key, eq condition
+    -- first 10 after_tuple 777
+    local conditions = { cond_funcs.eq('age', 90) }
+    local plan, err = select_plan.new(box.space.customers, conditions, {
+        first = 10,
+        after_tuple = after_tuple,
+    })
+
+    t.assert_equals(err, nil)
+    t.assert_type(plan, 'table')
+
+    t.assert_equals(plan.conditions, conditions)
+    t.assert_equals(plan.space_name, 'customers')
+    t.assert_equals(plan.index_id, 1)
+    t.assert_equals(plan.scan_value, {90}) -- after_tuple id
+    t.assert_equals(plan.after_tuple, after_tuple)
+    t.assert_equals(plan.scan_condition_num, 1)
+    t.assert_equals(plan.tarantool_iter, box.index.GE) -- inverted iterator
     t.assert_equals(plan.total_tuples_count, 10)
     t.assert_equals(plan.sharding_key, nil)
     t.assert_equals(plan.field_names, nil)