From c37c5abfeb89230dd3bb9c6fa0fc5a76b313fe85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= <markus.makela@mariadb.com>
Date: Mon, 3 Apr 2017 19:29:14 +0300
Subject: [PATCH] Use collectable resultset type for database mapping

When the databases are mapped, it is desirable to get the complete
response in one contiguous buffer. This removes the need to manually
process the partial packets in the router code.
---
 .../schemarouter/schemaroutersession.cc       | 52 ++++++-------------
 1 file changed, 16 insertions(+), 36 deletions(-)

diff --git a/server/modules/routing/schemarouter/schemaroutersession.cc b/server/modules/routing/schemarouter/schemaroutersession.cc
index 6ec69e713..cfe14c5ef 100644
--- a/server/modules/routing/schemarouter/schemaroutersession.cc
+++ b/server/modules/routing/schemarouter/schemaroutersession.cc
@@ -1032,29 +1032,18 @@ int SchemaRouterSession::inspect_backend_mapping_states(SBackend& bref,
     {
         if (bref->dcb() == (*it)->dcb() && !(*it)->is_mapped())
         {
-            if (bref->m_map_queue)
-            {
-                writebuf = gwbuf_append(bref->m_map_queue, writebuf);
-                bref->m_map_queue = NULL;
-            }
             enum showdb_response rc = parse_showdb_response(*it, &writebuf);
+
             if (rc == SHOWDB_FULL_RESPONSE)
             {
-                (*it)->m_mapped = true;
+                (*it)->set_mapped(true);
                 MXS_DEBUG("Received SHOW DATABASES reply from %s for session %p",
                           (*it)->backend()->server->unique_name,
                           m_client->session);
             }
-            else if (rc == SHOWDB_PARTIAL_RESPONSE)
-            {
-                bref->m_map_queue = writebuf;
-                writebuf = NULL;
-                MXS_DEBUG("Received partial SHOW DATABASES reply from %s for session %p",
-                          (*it)->backend()->server->unique_name,
-                          m_client->session);
-            }
             else
             {
+                ss_dassert(rc != SHOWDB_PARTIAL_RESPONSE);
                 DCB* client_dcb = NULL;
 
                 if ((m_state & INIT_FAILED) == 0)
@@ -1294,6 +1283,7 @@ enum showdb_response SchemaRouterSession::parse_showdb_response(SBackend& bref,
     {
         return SHOWDB_PARTIAL_RESPONSE;
     }
+    int n_eof = 0;
 
     ptr = (unsigned char*) buf->start;
 
@@ -1304,7 +1294,7 @@ enum showdb_response SchemaRouterSession::parse_showdb_response(SBackend& bref,
         return SHOWDB_FATAL_ERROR;
     }
 
-    if (bref->m_num_mapping_eof == 0)
+    if (n_eof == 0)
     {
         /** Skip column definitions */
         while (ptr < (unsigned char*) buf->end && !PTR_IS_EOF(ptr))
@@ -1319,7 +1309,7 @@ enum showdb_response SchemaRouterSession::parse_showdb_response(SBackend& bref,
             return SHOWDB_FATAL_ERROR;
         }
 
-        atomic_add(&bref->m_num_mapping_eof, 1);
+        n_eof++;
         /** Skip first EOF packet */
         ptr += gw_mysql_get_byte3(ptr) + 4;
     }
@@ -1353,9 +1343,9 @@ enum showdb_response SchemaRouterSession::parse_showdb_response(SBackend& bref,
         ptr += packetlen;
     }
 
-    if (ptr < (unsigned char*) buf->end && PTR_IS_EOF(ptr) && bref->m_num_mapping_eof == 1)
+    if (ptr < (unsigned char*) buf->end && PTR_IS_EOF(ptr) && n_eof == 1)
     {
-        atomic_add(&bref->m_num_mapping_eof, 1);
+        n_eof++;
         MXS_INFO("SHOW DATABASES fully received from %s.",
                  bref->backend()->server->unique_name);
     }
@@ -1371,7 +1361,7 @@ enum showdb_response SchemaRouterSession::parse_showdb_response(SBackend& bref,
     {
         rval = SHOWDB_DUPLICATE_DATABASES;
     }
-    else if (bref->m_num_mapping_eof == 2)
+    else if (n_eof == 2)
     {
         rval = SHOWDB_FULL_RESPONSE;
     }
@@ -1390,36 +1380,26 @@ enum showdb_response SchemaRouterSession::parse_showdb_response(SBackend& bref,
  */
 void SchemaRouterSession::gen_databaselist()
 {
-    DCB* dcb;
-    const char* query = "SHOW DATABASES";
-    GWBUF *buffer, *clone;
-    int i, rval = 0;
-    unsigned int len;
 
     for (BackendList::iterator it = m_backends.begin(); it != m_backends.end(); it++)
     {
-        (*it)->m_mapped = false;
-        (*it)->m_num_mapping_eof = 0;
+        (*it)->set_mapped(false);
     }
 
     m_state |= INIT_MAPPING;
     m_state &= ~INIT_UNINT;
-    len = strlen(query) + 1;
-    buffer = gwbuf_alloc(len + 4);
-    uint8_t *data = GWBUF_DATA(buffer);
-    *(data) = len;
-    *(data + 1) = len >> 8;
-    *(data + 2) = len >> 16;
-    *(data + 3) = 0x0;
-    *(data + 4) = 0x03;
-    memcpy(data + 5, query, strlen(query));
+
+    GWBUF *buffer = modutil_create_query("SHOW DATABASES");
+    gwbuf_set_type(buffer, GWBUF_TYPE_COLLECT_RESULT);
 
     for (BackendList::iterator it = m_backends.begin(); it != m_backends.end(); it++)
     {
         if ((*it)->in_use() && !(*it)->is_closed() &
             SERVER_IS_RUNNING((*it)->backend()->server))
         {
-            clone = gwbuf_clone(buffer);
+            GWBUF* clone = gwbuf_clone(buffer);
+            MXS_ABORT_IF_NULL(clone);
+
             if (!(*it)->write(clone))
             {
                 MXS_ERROR("Failed to write SHOW DATABASES to '%s'",