net.box: fix schema fetching from 1.10/2.1 servers

After 2.2.0-390-ga7c855e5b ("net.box: fetch '_vcollation' sysview into
the module") net.box fetches _vcollation view unconditionally, while the
view was added in 2.2.0-389-g3e3ef182f and, say, tarantool-1.10 and
tarantool-2.1 do not have it. This leads to a runtime error "Space '277'
does not exist" on a newer client that connects to an older server.

Now the view is fetched conditionally depending of a version of a
server: if it is above 2.2.1, then net.box will fetch it. Note: at the
time there are no release with a number above 2.2.1.

When _vcollation view is available, a collation in an index part will be
shown by its name (with 'collation' field), otherwise it will be shown
by its ID (in 'collation_id' field). For example:

Connect to tarantool 1.10:

 | tarantool> connection = require('net.box').connect('localhost:3301')
 | ---
 | ...
 |
 | tarantool> connection.space.s.index.sk.parts
 | ---
 | - - type: string
 |     is_nullable: false
 |     collation_id: 2
 |     fieldno: 2
 | ...

Connect to tarantool 2.2.1 (when it will be released):

 | tarantool> connection = require('net.box').connect('localhost:3301')
 | ---
 | ...
 |
 | tarantool> connection.space.s.index.sk.parts
 | ---
 | - - type: string
 |     is_nullable: false
 |     collation: unicode_ci
 |     fieldno: 2
 | ...

Fixes #4307.

src/box/lua/net_box.lua

@@ -84,6 +84,14 @@ local function decode_push(raw_data)
     return response[IPROTO_DATA_KEY][1], raw_end
 end
 
+local function version_id(major, minor, patch)
+    return bit.bor(bit.lshift(major, 16), bit.lshift(minor, 8), patch)
+end
+
+local function version_at_least(peer_version_id, major, minor, patch)
+    return peer_version_id >= version_id(major, minor, patch)
+end
+
 local method_encoder = {
     ping    = internal.encode_ping,
     call_16 = internal.encode_call_16,
@@ -735,17 +743,23 @@ local function create_transport(host, port, user, password, callback,
             set_state('active')
             return iproto_sm(schema_version)
         end
+        -- _vcollation view was added in 2.2.0-389-g3e3ef182f
+        local peer_has_vcollation = version_at_least(greeting.version_id,
+                                                     2, 2, 1)
         local select1_id = new_request_id()
         local select2_id = new_request_id()
-        local select3_id = new_request_id()
+        local select3_id
         local response = {}
         -- fetch everything from space _vspace, 2 = ITER_ALL
         encode_select(send_buf, select1_id, VSPACE_ID, 0, 2, 0, 0xFFFFFFFF, nil)
         -- fetch everything from space _vindex, 2 = ITER_ALL
         encode_select(send_buf, select2_id, VINDEX_ID, 0, 2, 0, 0xFFFFFFFF, nil)
         -- fetch everything from space _vcollation, 2 = ITER_ALL
-        encode_select(send_buf, select3_id, VCOLLATION_ID, 0, 2, 0, 0xFFFFFFFF,
-                      nil)
+        if peer_has_vcollation then
+            select3_id = new_request_id()
+            encode_select(send_buf, select3_id, VCOLLATION_ID, 0, 2, 0,
+                          0xFFFFFFFF, nil)
+        end
 
         schema_version = nil -- any schema_version will do provided that
                              -- it is consistent across responses
@@ -754,6 +768,8 @@ local function create_transport(host, port, user, password, callback,
             if err then return error_sm(err, hdr) end
             dispatch_response_iproto(hdr, body_rpos, body_end)
             local id = hdr[IPROTO_SYNC_KEY]
+            -- trick: omit check for peer_has_vcollation: id is
+            -- not nil
             if id == select1_id or id == select2_id or id == select3_id then
                 -- response to a schema query we've submitted
                 local status = hdr[IPROTO_STATUS_KEY]
@@ -774,9 +790,10 @@ local function create_transport(host, port, user, password, callback,
                 response[id] = body[IPROTO_DATA_KEY]
             end
         until response[select1_id] and response[select2_id] and
-              response[select3_id]
+              (not peer_has_vcollation or response[select3_id])
+        -- trick: response[select3_id] is nil when the key is nil
         callback('did_fetch_schema', schema_version, response[select1_id],
-                 response[select2_id],response[select3_id])
+                 response[select2_id], response[select3_id])
         set_state('active')
         return iproto_sm(schema_version)
     end
@@ -1269,17 +1286,23 @@ function remote_methods:_install_schema(schema_version, spaces, indices,
                 local pkcollationid = index[PARTS][k].collation
                 local pktype = index[PARTS][k][2] or index[PARTS][k].type
                 local pkfield = index[PARTS][k][1] or index[PARTS][k].field
+                -- resolve a collation name if a peer has
+                -- _vcollation view
                 local pkcollation = nil
-                if pkcollationid ~= nil then
+                if pkcollationid ~= nil and collations ~= nil then
                     pkcollation = collations[pkcollationid + 1][2]
                 end
 
                 local pk = {
                     type = pktype,
                     fieldno = pkfield + 1,
-                    collation = pkcollation,
                     is_nullable = pknullable
                 }
+                if collations == nil then
+                    pk.collation_id = pkcollationid
+                else
+                    pk.collation = pkcollation
+                end
                 idx.parts[k] = pk
             end
             idx.unique = not not index[OPTS].unique

test/box/net.box.result

@@ -2905,18 +2905,41 @@ c = net:connect(box.cfg.listen)
 box.internal.collation.create('test', 'ICU', 'ru-RU')
 ---
 ...
+collation_id = box.internal.collation.id_by_name('test')
+---
+...
 _ = space:create_index('sk', { type = 'tree', parts = {{1, 'str', collation = 'test'}}, unique = true })
 ---
 ...
 c:reload_schema()
 ---
 ...
-c.space.test.index.sk.parts
+parts = c.space.test.index.sk.parts
 ---
-- - type: string
-    is_nullable: false
-    collation: test
-    fieldno: 1
+...
+#parts == 1
+---
+- true
+...
+parts[1].fieldno == 1
+---
+- true
+...
+parts[1].type == 'string'
+---
+- true
+...
+parts[1].is_nullable == false
+---
+- true
+...
+if _TARANTOOL >= '2.2.1' then                    \
+    return parts[1].collation == 'test'          \
+else                                             \
+    return parts[1].collation_id == collation_id \
+end
+---
+- true
 ...
 c:close()
 ---

test/box/net.box.test.lua

@@ -1195,9 +1195,19 @@ c:close()
 box.schema.user.grant('guest', 'read', 'space', 'test')
 c = net:connect(box.cfg.listen)
 box.internal.collation.create('test', 'ICU', 'ru-RU')
+collation_id = box.internal.collation.id_by_name('test')
 _ = space:create_index('sk', { type = 'tree', parts = {{1, 'str', collation = 'test'}}, unique = true })
 c:reload_schema()
-c.space.test.index.sk.parts
+parts = c.space.test.index.sk.parts
+#parts == 1
+parts[1].fieldno == 1
+parts[1].type == 'string'
+parts[1].is_nullable == false
+if _TARANTOOL >= '2.2.1' then                    \
+    return parts[1].collation == 'test'          \
+else                                             \
+    return parts[1].collation_id == collation_id \
+end
 c:close()
 box.internal.collation.drop('test')
 space:drop()

test/box/stat_net.result

@@ -83,9 +83,9 @@ box.stat.net.CONNECTIONS.total
 ---
 - 4
 ...
-box.stat.net.REQUESTS.total
+box.stat.net.REQUESTS.total > 0
 ---
-- 17
+- true
 ...
 box.stat.net.CONNECTIONS.current
 ---
@@ -115,6 +115,9 @@ test_run:wait_cond(function() return box.stat.net.CONNECTIONS.current == 1 end,
 ---
 - true
 ...
+requests_total_saved = box.stat.net.REQUESTS.total
+---
+...
 future1 = cn:call('tweedledee', {}, {is_async = true})
 ---
 ...
@@ -149,9 +152,9 @@ test_run:wait_cond(function() return box.stat.net.REQUESTS.current == 0 end, WAI
 ---
 - true
 ...
-box.stat.net.REQUESTS.total
+box.stat.net.REQUESTS.total - requests_total_saved == 2
 ---
-- 19
+- true
 ...
 -- reset
 box.stat.reset()

test/box/stat_net.test.lua

@@ -29,7 +29,7 @@ cn.space.tweedledum:select() --small request
 box.stat.net.SENT.total > 0
 box.stat.net.RECEIVED.total > 0
 box.stat.net.CONNECTIONS.total
-box.stat.net.REQUESTS.total
+box.stat.net.REQUESTS.total > 0
 box.stat.net.CONNECTIONS.current
 box.stat.net.REQUESTS.current
 
@@ -41,6 +41,7 @@ test_run:wait_cond(function() return box.stat.net.CONNECTIONS.current == 2 end,
 cn3:close()
 test_run:wait_cond(function() return box.stat.net.CONNECTIONS.current == 1 end, WAIT_COND_TIMEOUT)
 
+requests_total_saved = box.stat.net.REQUESTS.total
 future1 = cn:call('tweedledee', {}, {is_async = true})
 test_run:wait_cond(function() return box.stat.net.REQUESTS.current == 1 end, WAIT_COND_TIMEOUT)
 future2 = cn:call('tweedledee', {}, {is_async = true})
@@ -50,7 +51,7 @@ ch:put(true)
 future1:wait_result()
 future2:wait_result()
 test_run:wait_cond(function() return box.stat.net.REQUESTS.current == 0 end, WAIT_COND_TIMEOUT)
-box.stat.net.REQUESTS.total
+box.stat.net.REQUESTS.total - requests_total_saved == 2
 
 -- reset
 box.stat.reset()