Hello! Thank you for review! New patch below. This time I wasn't
able to insert diff between two last versions, but I will do it
in next patches.

On 06/10/2018 12:04, imeevma@tarantool.org wrote:

At the moment all collations that don't have their "strength"
option set works the same way as ones with this option set to
"identical". It is not efficient, according to ICU Comparison
Levels. This patch updates this option of old collations and set
its default value to "primary" for new ones.

Closes #3573
---
Branch: https://github.com/tarantool/tarantool/tree/imeevma/gh-3573-fix-collation-strength
Issue: https://github.com/tarantool/tarantool/issues/3573

  src/box/bootstrap.snap       | Bin 1888 -> 1886 bytes
  src/box/coll_id_def.c        |   4 +-
  src/box/lua/upgrade.lua      |  29 ++++++++++++++-
  src/coll.c                   |  33 ++++++++--------
  src/coll_def.c               |   1 -
  src/coll_def.h               |   3 +-
  test/box-py/bootstrap.result |   2 +-
  test/box/ddl.result          |   6 +--
  test/box/tree_pk.result      |   2 +-
  test/box/tree_pk.test.lua    |   2 +-
  test/sql/collation.result    |  87 +++++++++++++++++++++++++++++++++++++++++++
  test/sql/collation.test.lua  |  32 ++++++++++++++++
  test/unit/coll.cpp           |   2 +
  13 files changed, 176 insertions(+), 27 deletions(-)

diff --git a/src/box/bootstrap.snap b/src/box/bootstrap.snap

1. Please, remove binary diff before sending an email.

index 65739384a66d6ba4a538553ccf4677536ba15280..84b27c0d8b9d6d683692e2ef55034ffcc68d11d0 100644
GIT binary patch
delta 1884
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diff --git a/src/box/lua/upgrade.lua b/src/box/lua/upgrade.lua
index d9c2ae4..07cace0 100644
--- a/src/box/lua/upgrade.lua
+++ b/src/box/lua/upgrade.lua
@@ -578,6 +578,32 @@ local function upgrade_to_2_1_0()
      box.space._schema:format(format)
  end
  +--------------------------------------------------------------------------------
+-- Tarantool 2.1.1
+--------------------------------------------------------------------------------
+
+function update_collation_strength_field()
+    local _collation = box.space[box.schema.COLLATION_ID]
+    local _format = _collation:format()
+    for _, collation in ipairs(_collation:select()) do
+        if (collation.opts.strength == nil) then
+            local old_collation = _collation:get{collation.id}
+            local new_collation = {}
+            for _,field in ipairs(_format) do
+                new_collation[field.name] = old_collation[field.name]
+            end
+            new_collation.opts.strength = 'identical'
+            _collation:delete{old_collation.id}
+            _collation:insert(_collation:frommap(new_collation))

2. This looks much simpler:

@@ -584,17 +584,11 @@ end
 
 function update_collation_strength_field()
     local _collation = box.space[box.schema.COLLATION_ID]
-    local _format = _collation:format()
     for _, collation in ipairs(_collation:select()) do
-        if (collation.opts.strength == nil) then
-            local old_collation = _collation:get{collation.id}
-            local new_collation = {}
-            for _,field in ipairs(_format) do
-                new_collation[field.name] = old_collation[field.name]
-            end
-            new_collation.opts.strength = 'identical'
-            _collation:delete{old_collation.id}
-            _collation:insert(_collation:frommap(new_collation))
+        if collation.opts.strength == nil then
+            local collation = _collation:get{collation.id}:totable()
+            collation[6].strength = 'identical'
+            _collation:replace(collation)
         end
     end
 end


I did not test it though. Please, apply and debug if
necessary.

+        end
+    end
+end
diff --git a/test/sql/collation.result b/test/sql/collation.result
index 79ba9ab..3c53be1 100644
--- a/test/sql/collation.result
+++ b/test/sql/collation.result
@@ -110,3 +110,90 @@ cn:close()
  box.schema.user.revoke('guest', 'read,write,execute', 'universe')
  ---
  ...
+--
+-- gh-3573: Strength in the _collation space
+-- Collation without 'strength' option set now works as one with
+-- 'strength' set to 'primary'.
+--
+box.internal.collation.create('c0', 'ICU', 'unicode')
+---
+...
+box.internal.collation.create('c1', 'ICU', 'unicode', {strength='primary'})
+---
+...
+box.internal.collation.create('c2', 'ICU', 'unicode', {strength='secondary'})
+---
+...
+box.internal.collation.create('c5', 'ICU', 'unicode', {strength='identical'})
+---
+...
+box.sql.execute([[create table tc (id int primary key autoincrement, s0 string collate "c0", s1 string collate "c1", s2 string collate "c2", s5 string collate "c5")]])
+---
+...
+box.sql.execute([[insert into tc values (null, 'a', 'a', 'a', 'a')]])
+---
+...
+box.sql.execute([[insert into tc values (null, 'A', 'A', 'A', 'A')]])
+---
+...
+box.sql.execute([[insert into tc values (null, 'á', 'á', 'á', 'á')]])
+---
+...
+box.sql.execute([[insert into tc values (null, 'â', 'â', 'â', 'â')]])
+---
+...
+box.sql.execute([[select * from tc where s0 = 'a']])
+---
+- - [1, 'a', 'a', 'a', 'a']
+  - [2, 'A', 'A', 'A', 'A']
+  - [3, 'á', 'á', 'á', 'á']
+  - [4, 'â', 'â', 'â', 'â']
+...
+box.sql.execute([[select * from tc where s1 = 'a']])
+---
+- - [1, 'a', 'a', 'a', 'a']
+  - [2, 'A', 'A', 'A', 'A']
+  - [3, 'á', 'á', 'á', 'á']
+  - [4, 'â', 'â', 'â', 'â']
+...
+box.sql.execute([[select * from tc where s2 = 'a']])
+---
+- - [1, 'a', 'a', 'a', 'a']
+  - [2, 'A', 'A', 'A', 'A']
+...
+box.sql.execute([[select * from tc where s5 = 'a']])
+---
+- - [1, 'a', 'a', 'a', 'a']
+...
+a = box.sql.execute([[select id from tc where s0 = 'a']])
+---
+...
+b = box.sql.execute([[select id from tc where s1 = 'a']])
+---
+...
+count = 0
+---
+...
+for k,v in pairs(a) do if (a[k][1] ~= b[k][1]) then count = count + 1 end end

3. You printed both a and b whole above and they are the same. Why do you
need this additional check in a cycle?