Bug#35333, "If Federated table can't connect to remote host, can't retrieve metadata"

Improved error handling such that queries against Information_Schema.Tables won't
fail if a Federated table is unable to connect to remote host.



sql/sql_show.cc:
  If Handler::Info() fails, save error text in TABLE COMMENTS column, clear error.

mysql-test/r/federated_bug_35333.result

+#
+# Bug 35333 "If a Federated table can't connect to the remote hose, can't retrieve metadata"
+#
+# Queries such as SHOW TABLE STATUS and SELECT * FROM INFORMATION_SCHEMA.TABLES fail
+# when encountering a federated table that cannot connect to its remote table.
+#
+# The fix is to store the error text in the TABLE COMMENTS column of I_S.TABLES, clear
+# the remote connection error and push a warning instead. This allows the SELECT operation
+# to complete while still indicating a problem. This fix applies to any non-fatal system
+# error that occurs during a query against I_S.TABLES.de
+stop slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+reset master;
+reset slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+start slave;
+stop slave;
+DROP DATABASE IF EXISTS federated;
+CREATE DATABASE federated;
+DROP DATABASE IF EXISTS federated;
+CREATE DATABASE federated;
+CREATE DATABASE IF NOT EXISTS realdb;
+DROP TABLE IF EXISTS realdb.t0;
+DROP TABLE IF EXISTS federated.t0;
+#
+# Create the base table to be referenced
+#
+CREATE TABLE realdb.t0 (a text, b text) ENGINE=MYISAM;
+#
+# Create a federated table with a bogus port number
+#
+CREATE TABLE federated.t0 (a text, b text) ENGINE=FEDERATED
+CONNECTION='mysql://root@127.0.0.1:63333/realdb/t0';
+#
+# Trigger a federated system error during a INFORMATION_SCHEMA.TABLES query
+#
+SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE, ROW_FORMAT, TABLE_ROWS, DATA_LENGTH, TABLE_COMMENT
+FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'realdb' or TABLE_SCHEMA = 'federated';
+TABLE_SCHEMA	TABLE_NAME	TABLE_TYPE	ENGINE	ROW_FORMAT	TABLE_ROWS	DATA_LENGTH	TABLE_COMMENT
+federated	t0		NULL	NULL	NULL	NULL	Unable to connect to foreign data source: Can't connect to MySQL server on '127.
+realdb	t0	BASE TABLE	MyISAM	Dynamic	0	0	
+Warnings:
+Warning	1429	Unable to connect to foreign data source: Can't connect to MySQL server on '127.0.0.1' (socket errno)
+SHOW WARNINGS;
+Level	Code	Message
+Warning	1429	Unable to connect to foreign data source: Can't connect to MySQL server on '127.0.0.1' (socket errno)
+#
+# Create a MyISAM table then corrupt the file
+#
+USE realdb;
+CREATE TABLE t1 (c1 int) ENGINE=MYISAM;
+#
+# Corrupt the MyISAM table by deleting the base file
+#
+#
+# Trigger a MyISAM system error during an INFORMATION_SCHEMA.TABLES query
+#
+SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE, ROW_FORMAT, TABLE_ROWS, DATA_LENGTH, TABLE_COMMENT
+FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1';
+TABLE_SCHEMA	TABLE_NAME	TABLE_TYPE	ENGINE	ROW_FORMAT	TABLE_ROWS	DATA_LENGTH	TABLE_COMMENT
+realdb	t1	BASE TABLE	NULL	NULL	NULL	NULL	Can't find file: 't1' (errno: 2)
+Warnings:
+Warning	1017	Can't find file: 't1' (errno: 2)
+SHOW WARNINGS;
+Level	Code	Message
+Warning	1017	Can't find file: 't1' (errno: 2)
+#
+# Cleanup
+#
+DROP TABLE IF EXISTS realdb.t0;
+DROP TABLE IF EXISTS federated.t0;
+DROP DATABASE realdb;
+DROP TABLE IF EXISTS federated.t1;
+DROP DATABASE IF EXISTS federated;
+DROP TABLE IF EXISTS federated.t1;
+DROP DATABASE IF EXISTS federated;

mysql-test/r/information_schema.result

@@ -1053,6 +1053,8 @@ select table_type from information_schema.tables
 where table_name="v1";
 table_type
 VIEW
+Warnings:
+Warning	1356	View 'test.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
 drop view v1;
 create temporary table t1(f1 int, index(f1));
 show columns from t1;

mysql-test/r/information_schema_db.result

@@ -65,10 +65,14 @@ select table_name, table_type, table_comment from information_schema.tables
 where table_schema='inf%' and func2();
 table_name	table_type	table_comment
 v1	VIEW	View 'inf%.v1' references invalid table(s) or column(s) or function(s) or define
+Warnings:
+Warning	1356	View 'inf%.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
 select table_name, table_type, table_comment from information_schema.tables
 where table_schema='inf%' and func2();
 table_name	table_type	table_comment
 v1	VIEW	View 'inf%.v1' references invalid table(s) or column(s) or function(s) or define
+Warnings:
+Warning	1356	View 'inf%.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
 drop view v1;
 drop function func1;
 drop function func2;

mysql-test/r/show_check.result

@@ -622,6 +622,8 @@ flush tables;
 SHOW TABLE STATUS like 't1';
 Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
 t1	NULL	NULL	NULL	NULL	#	#	#	#	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Incorrect information in file: './test/t1.frm'
+Warnings:
+Warning	1033	Incorrect information in file: './test/t1.frm'
 show create table t1;
 ERROR HY000: Incorrect information in file: './test/t1.frm'
 drop table t1;

mysql-test/r/view.result

@@ -840,6 +840,8 @@ show table status;
 Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
 t1	MyISAM	10	Fixed	0	0	0	#	1024	0	NULL	#	#	NULL	latin1_swedish_ci	NULL		
 v1	NULL	NULL	NULL	NULL	NULL	NULL	#	NULL	NULL	NULL	#	#	NULL	NULL	NULL	NULL	View 'test.v1' references invalid table(s) or column(s) or function(s) or define
+Warnings:
+Warning	1356	View 'test.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
 drop view v1;
 drop table t1;
 create view v1 as select 99999999999999999999999999999999999999999999999999999 as col1;

mysql-test/t/federated_bug_35333.test

+--echo #
+--echo # Bug 35333 "If a Federated table can't connect to the remote hose, can't retrieve metadata"
+--echo #
+--echo # Queries such as SHOW TABLE STATUS and SELECT * FROM INFORMATION_SCHEMA.TABLES fail
+--echo # when encountering a federated table that cannot connect to its remote table.
+--echo #
+--echo # The fix is to store the error text in the TABLE COMMENTS column of I_S.TABLES, clear
+--echo # the remote connection error and push a warning instead. This allows the SELECT operation
+--echo # to complete while still indicating a problem. This fix applies to any non-fatal system
+--echo # error that occurs during a query against I_S.TABLES.de
+
+--source include/federated.inc
+
+--disable_warnings
+CREATE DATABASE IF NOT EXISTS realdb;
+# Federated database exists
+DROP TABLE IF EXISTS realdb.t0;
+DROP TABLE IF EXISTS federated.t0;
+--enable_warnings
+
+--echo #
+--echo # Create the base table to be referenced
+--echo #
+CREATE TABLE realdb.t0 (a text, b text) ENGINE=MYISAM;
+
+--echo #
+--echo # Create a federated table with a bogus port number
+--echo #
+CREATE TABLE federated.t0 (a text, b text) ENGINE=FEDERATED
+    CONNECTION='mysql://root@127.0.0.1:63333/realdb/t0';
+
+#--warning ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+
+--echo #
+--echo # Trigger a federated system error during a INFORMATION_SCHEMA.TABLES query
+--echo #
+# Remove O/S-specific socket error
+--replace_regex /\(.*\)/(socket errno)/
+SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE, ROW_FORMAT, TABLE_ROWS, DATA_LENGTH, TABLE_COMMENT
+       FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'realdb' or TABLE_SCHEMA = 'federated';
+
+# Remove O/S-specific socket error
+--replace_regex /\(.*\)/(socket errno)/
+SHOW WARNINGS;
+
+--echo #
+--echo # Create a MyISAM table then corrupt the file
+--echo #
+USE realdb;
+CREATE TABLE t1 (c1 int) ENGINE=MYISAM;
+--echo #
+--echo # Corrupt the MyISAM table by deleting the base file
+--echo #
+let $MYSQLD_DATADIR= `SELECT @@datadir`;
+--remove_file $MYSQLD_DATADIR/realdb/t1.MYD
+--remove_file $MYSQLD_DATADIR/realdb/t1.MYI
+
+--echo #
+--echo # Trigger a MyISAM system error during an INFORMATION_SCHEMA.TABLES query
+--echo #
+SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE, ROW_FORMAT, TABLE_ROWS, DATA_LENGTH, TABLE_COMMENT
+       FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1';
+
+SHOW WARNINGS;
+--echo #
+--echo # Cleanup
+--echo #
+--disable_warnings
+DROP TABLE IF EXISTS realdb.t0;
+DROP TABLE IF EXISTS federated.t0;
+DROP DATABASE realdb;
+--enable_warnings
+
+--source include/federated_cleanup.inc

sql/sql_show.cc

@@ -2486,28 +2486,28 @@ static int get_schema_tables_record(THD *thd, TABLE_LIST *tables,
 {
   const char *tmp_buff;
   MYSQL_TIME time;
+  int info_error= 0;
   CHARSET_INFO *cs= system_charset_info;
   DBUG_ENTER("get_schema_tables_record");
 
   restore_record(table, s->default_values);
   table->field[1]->store(base_name, (uint) strlen(base_name), cs);
   table->field[2]->store(file_name, (uint) strlen(file_name), cs);
+
   if (res)
   {
-    /*
-      there was errors during opening tables
-    */
-    const char *error= thd->net.last_error;
+    /* There was a table open error, so set the table type and return */
     if (tables->view)
       table->field[3]->store(STRING_WITH_LEN("VIEW"), cs);
     else if (tables->schema_table)
       table->field[3]->store(STRING_WITH_LEN("SYSTEM VIEW"), cs);
     else
       table->field[3]->store(STRING_WITH_LEN("BASE TABLE"), cs);
-    table->field[20]->store(error, (uint) strlen(error), cs);
-    thd->clear_error();
+
+    goto err;
   }
-  else if (tables->view)
+
+  if (tables->view)
   {
     table->field[3]->store(STRING_WITH_LEN("VIEW"), cs);
     table->field[20]->store(STRING_WITH_LEN("VIEW"), cs);
@@ -2518,8 +2518,15 @@ static int get_schema_tables_record(THD *thd, TABLE_LIST *tables,
     TABLE_SHARE *share= show_table->s;
     handler *file= show_table->file;
 
-    file->info(HA_STATUS_VARIABLE | HA_STATUS_TIME | HA_STATUS_AUTO |
-               HA_STATUS_NO_LOCK);
+    if (!file)
+      goto err;
+
+    if ((info_error= file->info(HA_STATUS_VARIABLE |
+                                HA_STATUS_TIME |
+                                HA_STATUS_AUTO |
+                                HA_STATUS_NO_LOCK)) != 0)
+      goto err;
+
     if (share->tmp_table == SYSTEM_TMP_TABLE)
       table->field[3]->store(STRING_WITH_LEN("SYSTEM VIEW"), cs);
     else if (share->tmp_table)
@@ -2665,6 +2672,25 @@ static int get_schema_tables_record(THD *thd, TABLE_LIST *tables,
       }
     }
   }
+
+err:
+  if (res || info_error)
+  {
+    /*
+      If an error was encountered, push a warning, set the TABLE COMMENT
+      column with the error text, and clear the error so that the operation
+      can continue.
+    */
+    const char *error= thd->net.last_error;
+    if (error)
+    {
+      table->field[20]->store(error, strlen(error), cs);
+      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                  thd->net.last_errno, thd->net.last_error);
+      thd->clear_error();
+    }
+  }
+
   DBUG_RETURN(schema_table_store_record(thd, table));
 }