Fix ignoring opts.limit on crud.pairs (#173)

Author: dokshina

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 
 * Compatibility with Tarantool versions that don't support key_def and merger modules.
+* Ignoring `opts.first` on `crud.pairs` call
 
 ## [0.7.0] - 2021-05-27
 

crud/select/compat/select.lua

@@ -115,6 +115,7 @@ local function build_select_iterator(space_name, user_conditions, opts)
     end
 
     return {
+        tuples_limit = tuples_limit,
         merger = merger,
         space_format = filtered_space_format,
     }
@@ -166,18 +167,23 @@ function select_module.pairs(space_name, user_conditions, opts)
         error(string.format("Failed to generate iterator: %s", err))
     end
 
-    if opts.use_tomap ~= true then
-        return iter.merger:pairs()
+    local gen, param, state = iter.merger:pairs()
+    if opts.use_tomap == true then
+        gen, param, state = gen:map(function(tuple)
+            local result
+            result, err = utils.unflatten(tuple, iter.space_format)
+            if err ~= nil then
+                error(string.format("Failed to unflatten next object: %s", err))
+            end
+            return result
+        end)
     end
 
-    return iter.merger:pairs():map(function(tuple)
-        local result
-        result, err = utils.unflatten(tuple, iter.space_format)
-        if err ~= nil then
-            error(string.format("Failed to unflatten next object: %s", err))
-        end
-        return result
-    end)
+    if iter.tuples_limit ~= nil then
+        gen, param, state = gen:take_n(iter.tuples_limit)
+    end
+
+    return gen, param, state
 end
 
 local function select_module_call_xc(space_name, user_conditions, opts)

crud/select/compat/select_old.lua

@@ -211,6 +211,11 @@ function select_module.pairs(space_name, user_conditions, opts)
         error(string.format("Failed to generate iterator: %s", err))
     end
 
+    local tuples_limit = opts.first
+    if tuples_limit ~= nil then
+        tuples_limit = math.abs(tuples_limit)
+    end
+
     local gen = function(_, iter)
         local tuple, err = iter:get()
         if tuple == nil then
@@ -232,7 +237,13 @@ function select_module.pairs(space_name, user_conditions, opts)
         return iter, result
     end
 
-    return fun.iter(gen, nil, iter)
+    local gen, param, state = fun.iter(gen, nil, iter)
+
+    if tuples_limit ~= nil then
+        gen, param, state = gen:take_n(tuples_limit)
+    end
+
+    return gen, param, state
 end
 
 function select_module.call(space_name, user_conditions, opts)

test/integration/pairs_test.lua

@@ -254,6 +254,49 @@ pgroup:add('test_le_condition_with_index', function(g)
     t.assert_equals(objects, helpers.get_objects_by_idxs(customers, {1})) -- in age order
 end)
 
+pgroup:add('test_first', function(g)
+    local customers = helpers.insert_objects(g, 'customers', {
+        {
+            id = 1, name = "Elizabeth", last_name = "Jackson",
+            age = 12, city = "New York",
+        }, {
+            id = 2, name = "Mary", last_name = "Brown",
+            age = 46, city = "Los Angeles",
+        }, {
+            id = 3, name = "David", last_name = "Smith",
+            age = 33, city = "Los Angeles",
+        },
+    })
+
+    table.sort(customers, function(obj1, obj2) return obj1.id < obj2.id end)
+
+    -- w/ tomap
+    local objects, err = g.cluster.main_server.net_box:eval([[
+        local crud = require('crud')
+        local objects = {}
+        for _, object in crud.pairs('customers', nil, {first = 2, use_tomap = true}) do
+            table.insert(objects, object)
+        end
+        return objects
+    ]])
+    t.assert_equals(err, nil)
+    t.assert_equals(objects, helpers.get_objects_by_idxs(customers, {1, 2}))
+
+    local tuples, err = g.cluster.main_server.net_box:eval([[
+        local crud = require('crud')
+        local tuples = {}
+        for _, tuple in crud.pairs('customers', nil, {first = 2}) do
+            table.insert(tuples, tuple)
+        end
+        return tuples
+    ]])
+    t.assert_equals(err, nil)
+    t.assert_equals(tuples, {
+        {1, 477, 'Elizabeth', 'Jackson', 12, 'New York'},
+        {2, 401, 'Mary', 'Brown', 46, 'Los Angeles'},
+    })
+end)
+
 pgroup:add('test_negative_first', function(g)
     local customers = helpers.insert_objects(g, 'customers',{
         {