Abstract the session default database

The default database can now be manipulated with a set of functions
exposed by the maxscale/protocol/mysql.h header. This removes the need to
handle the structures themselves in the modules and is a step towards
moving the dcb->data contents inside the session.

include/maxscale/protocol/mysql.h

@@ -485,4 +485,23 @@ mysql_server_cmd_t mxs_mysql_current_command(MXS_SESSION* session);
 void mysql_num_response_packets(GWBUF *buf, uint8_t cmd,
                                 int* npackets, size_t *nbytes);
 
+/**
+ * @brief Return current database of the session
+ *
+ * If no active database is in use, the database is an empty string.
+ *
+ * @param session Session to inspect
+ *
+ * @return The current database
+ */
+const char* mxs_mysql_get_current_db(MXS_SESSION* session);
+
+/**
+ * @brief Set the currently active database for a session
+ *
+ * @param session Session to modify
+ * @param db      The new database
+ */
+void mxs_mysql_set_current_db(MXS_SESSION* session, const char* db);
+
 MXS_END_DECLS

server/modules/filter/cache/CMakeLists.txt

@@ -17,7 +17,7 @@ if (JANSSON_FOUND)
     storagefactory.cc
     storagereal.cc
     )
-  target_link_libraries(cache maxscale-common ${JANSSON_LIBRARIES})
+  target_link_libraries(cache maxscale-common ${JANSSON_LIBRARIES} MySQLCommon)
   set_target_properties(cache PROPERTIES VERSION "1.0.0")
   set_target_properties(cache PROPERTIES LINK_FLAGS -Wl,-z,defs)
   install_module(cache core)

server/modules/filter/cache/cachefiltersession.cc

@@ -205,15 +205,15 @@ CacheFilterSession* CacheFilterSession::Create(Cache* pCache, MXS_SESSION* pSess
     ss_dassert(pSession->client_dcb);
     ss_dassert(pSession->client_dcb->data);
 
-    MYSQL_session *pMysqlSession = (MYSQL_session*)pSession->client_dcb->data;
+    const char* zDb = mxs_mysql_get_current_db(pSession);
     char* zDefaultDb = NULL;
 
-    if (pMysqlSession->db[0] != 0)
+    if (zDb[0] != 0)
     {
-        zDefaultDb = MXS_STRDUP(pMysqlSession->db);
+        zDefaultDb = MXS_STRDUP(zDb);
     }
 
-    if ((pMysqlSession->db[0] == 0) || zDefaultDb)
+    if ((zDb[0] == 0) || zDefaultDb)
     {
         pCacheFilterSession = new (std::nothrow) CacheFilterSession(pSession, pCache, zDefaultDb);
 

server/modules/filter/dbfwfilter/CMakeLists.txt

@@ -7,13 +7,13 @@ if(BISON_FOUND AND FLEX_FOUND)
   include_directories(${CMAKE_CURRENT_BINARY_DIR})
   include_directories(${CMAKE_CURRENT_SOURCE_DIR})
   add_library(dbfwfilter SHARED dbfwfilter.c ${BISON_ruleparser_OUTPUTS} ${FLEX_token_OUTPUTS})
-  target_link_libraries(dbfwfilter maxscale-common)
+  target_link_libraries(dbfwfilter maxscale-common MySQLCommon)
   set_target_properties(dbfwfilter PROPERTIES VERSION "1.0.0")
   install_module(dbfwfilter core)
 
   # The offline rule check utility
   add_executable(dbfwchk dbfw_rule_check.c ${BISON_ruleparser_OUTPUTS} ${FLEX_token_OUTPUTS})
-  target_link_libraries(dbfwchk maxscale-common)
+  target_link_libraries(dbfwchk maxscale-common MySQLCommon)
   install_executable(dbfwchk core)
 
 else()

server/modules/filter/dbfwfilter/dbfwfilter.c

@@ -1745,7 +1745,7 @@ GWBUF* gen_dummy_error(FW_SESSION* session, char* msg)
     }
 
     dcb = session->session->client_dcb;
-    mysql_session = (MYSQL_session*) dcb->data;
+    const char* db = mxs_mysql_get_current_db(session->session);
     errlen = msg != NULL ? strlen(msg) : 0;
     errmsg = (char*) MXS_MALLOC((512 + errlen) * sizeof(char));
 
@@ -1755,14 +1755,14 @@ GWBUF* gen_dummy_error(FW_SESSION* session, char* msg)
     }
 
 
-    if (mysql_session->db[0] == '\0')
+    if (db[0] == '\0')
     {
         sprintf(errmsg, "Access denied for user '%s'@'%s'", dcb->user, dcb->remote);
     }
     else
     {
         sprintf(errmsg, "Access denied for user '%s'@'%s' to database '%s'",
-                dcb->user, dcb->remote, mysql_session->db);
+                dcb->user, dcb->remote, db);
     }
 
     if (msg != NULL)

server/modules/filter/mqfilter/mqfilter.c

@@ -807,21 +807,15 @@ void pushMessage(MQ_INSTANCE *instance, amqp_basic_properties_t* prop, char* msg
 static MXS_FILTER_SESSION *
 newSession(MXS_FILTER *instance, MXS_SESSION *session)
 {
-    MYSQL_session *sessauth = session->client_dcb->data;
+    const char *db = mxs_mysql_get_current_db(session);
-    char *db = sessauth->db;
+    char* my_db = NULL;
-    if (db)
+
+    if (*db)
     {
-        if (strnlen(db, 128) > 0)
+        my_db = MXS_STRDUP(my_db);
+        if (!my_db)
         {
-            db = MXS_STRDUP(db);
+            return NULL;
-            if (!db)
-            {
-                return NULL;
-            }
-        }
-        else
-        {
-            db = NULL;
         }
     }
 
@@ -832,11 +826,11 @@ newSession(MXS_FILTER *instance, MXS_SESSION *session)
         my_session->was_query = false;
         my_session->uid = NULL;
         my_session->session = session;
-        my_session->db = db;
+        my_session->db = my_db;
     }
     else
     {
-        MXS_FREE(db);
+        MXS_FREE(my_db);
     }
 
     return (MXS_FILTER_SESSION*)my_session;

server/modules/protocol/MySQL/mysql_common.c

@@ -1587,3 +1587,15 @@ mysql_server_cmd_t mxs_mysql_current_command(MXS_SESSION* session)
     MySQLProtocol* proto = (MySQLProtocol*)session->client_dcb->protocol;
     return proto->current_command;
 }
+
+const char* mxs_mysql_get_current_db(MXS_SESSION* session)
+{
+    MYSQL_session* data = (MYSQL_session*)session->client_dcb->data;
+    return data->db;
+}
+
+void mxs_mysql_set_current_db(MXS_SESSION* session, const char* db)
+{
+    MYSQL_session* data = (MYSQL_session*)session->client_dcb->data;
+    snprintf(data->db, sizeof(data->db), "%s", db);
+}

server/modules/routing/readwritesplit/rwsplit_mysql.cc

@@ -380,8 +380,7 @@ bool execute_sescmd_in_backend(backend_ref_t *backend_ref)
             MYSQL_session* data;
             unsigned int qlen;
 
-            data = (MYSQL_session*)dcb->session->client_dcb->data;
+            mxs_mysql_set_current_db(dcb->session, "");
-            *data->db = 0;
             tmpbuf = scur->scmd_cur_cmd->my_sescmd_buf;
             qlen = MYSQL_GET_PAYLOAD_LEN((unsigned char *) GWBUF_DATA(tmpbuf));
             if (qlen)
@@ -394,8 +393,10 @@ bool execute_sescmd_in_backend(backend_ref_t *backend_ref)
                     qlen = MYSQL_DATABASE_MAXLEN;
                 }
 
-                memcpy(data->db, (char*)GWBUF_DATA(tmpbuf) + 5, qlen);
+                char db[qlen + 1];
-                data->db[qlen] = 0;
+                memcpy(db, (char*)GWBUF_DATA(tmpbuf) + 5, qlen);
+                db[qlen] = 0;
+                mxs_mysql_set_current_db(dcb->session, db);
             }
         }
     /** Fallthrough */

server/modules/routing/readwritesplit/rwsplit_tmp_table_multi.cc

@@ -54,8 +54,8 @@ void check_drop_tmp_table(ROUTER_CLIENT_SES *router_cli_ses, GWBUF *querybuf)
 
         for (size_t i = 0; i < n_infos; i++)
         {
-            MYSQL_session* data = static_cast<MYSQL_session*>(router_cli_ses->client_dcb->data);
+            const char* db = mxs_mysql_get_current_db(router_cli_ses->client_dcb->session);
-            std::string table = info[i].database ? info[i].database : data->db;
+            std::string table = info[i].database ? info[i].database : db;
             table += ".";
 
             if (info[i].table)
@@ -95,8 +95,8 @@ bool is_read_tmp_table(ROUTER_CLIENT_SES *router_cli_ses,
 
         for (size_t i = 0; i < n_infos; i++)
         {
-            MYSQL_session* data = static_cast<MYSQL_session*>(router_cli_ses->client_dcb->data);
+            const char* db = mxs_mysql_get_current_db(router_cli_ses->client_dcb->session);
-            std::string table = info[i].database ? info[i].database : data->db;
+            std::string table = info[i].database ? info[i].database : db;
             table += ".";
 
             if (info[i].table)
@@ -142,8 +142,8 @@ void check_create_tmp_table(ROUTER_CLIENT_SES *router_cli_ses,
 
         if (tblname && *tblname)
         {
-            MYSQL_session* data = static_cast<MYSQL_session*>(router_cli_ses->client_dcb->data);
+            const char* db = mxs_mysql_get_current_db(router_cli_ses->client_dcb->session);
-            table += data->db;
+            table += db;
             table += ".";
             table += tblname;
         }

server/modules/routing/schemarouter/CMakeLists.txt

@@ -1,5 +1,5 @@
 add_library(schemarouter SHARED schemarouter.cc schemarouterinstance.cc schemaroutersession.cc shard_map.cc session_command.cc)
-target_link_libraries(schemarouter maxscale-common)
+target_link_libraries(schemarouter maxscale-common MySQLCommon)
 add_dependencies(schemarouter pcre2)
 set_target_properties(schemarouter PROPERTIES VERSION "1.0.0")
 install_module(schemarouter core)

server/modules/routing/schemarouter/schemaroutersession.cc

@@ -46,28 +46,23 @@ SchemaRouterSession::SchemaRouterSession(MXS_SESSION* session, SchemaRouter* rou
 {
     char db[MYSQL_DATABASE_MAXLEN + 1] = "";
     MySQLProtocol* protocol = (MySQLProtocol*)session->client_dcb->protocol;
-    MYSQL_session* data = (MYSQL_session*)session->client_dcb->data;
     bool using_db = false;
     bool have_db = false;
+    const char* current_db = mxs_mysql_get_current_db(session);
 
     /* To enable connecting directly to a sharded database we first need
      * to disable it for the client DCB's protocol so that we can connect to them*/
     if (protocol->client_capabilities & GW_MYSQL_CAPABILITIES_CONNECT_WITH_DB &&
-        (have_db = strnlen(data->db, MYSQL_DATABASE_MAXLEN) > 0))
+        (have_db = *current_db))
     {
         protocol->client_capabilities &= ~GW_MYSQL_CAPABILITIES_CONNECT_WITH_DB;
-        strcpy(db, data->db);
+        strcpy(db, current_db);
-        *data->db = 0;
+        mxs_mysql_set_current_db(session, "");
         using_db = true;
         MXS_INFO("Client logging in directly to a database '%s', "
                  "postponing until databases have been mapped.", db);
     }
 
-    if (!have_db)
-    {
-        MXS_INFO("Client'%s' connecting with empty database.", data->user);
-    }
-
     if (using_db)
     {
         m_state |= INIT_USE_DB;