BUG#11751793 - 42784: ARCHIVE TABLES CAUSE 100% CPU USAGE

                      AND HANG IN SHOW TABLE STATUS.

ISSUE: Table corruption due to concurrent queries.
       Different threads running insert and check
       query leads to table corruption. Not properly locked,
       rows are inserted in between check query.

SOLUTION: In check query mutex lock is acquired
          for a longer time to handle concurrent
          insert and check query.

NOTE: Additionally we backported the fix for CHECKSUM
      issue(bug#11758979).

mysql-test/r/archive.result

@@ -12772,3 +12772,22 @@ a	b	c	d	e	f
 -1	b	c	d	e	1
 DROP TABLE t1;
 SET sort_buffer_size=DEFAULT;
+#
+# BUG#11758979 - 51252: ARCHIVE TABLES CAUSE 100% CPU USAGE
+#                       AND HANG IN SHOW TABLE STATUS
+# (to be executed with valgrind)
+CREATE TABLE t1(a BLOB, b VARCHAR(200)) ENGINE=ARCHIVE;
+INSERT INTO t1 VALUES(NULL, '');
+FLUSH TABLE t1;
+# we need this select to workaround BUG#11764364
+SELECT * FROM t1;
+a	b
+NULL	
+CHECKSUM TABLE t1 EXTENDED;
+Table	Checksum
+test.t1	286155052
+FLUSH TABLE t1;
+OPTIMIZE TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	optimize	status	OK
+DROP TABLE t1;

mysql-test/t/archive.test

@@ -1693,3 +1693,17 @@ INSERT INTO t1 SELECT t1.* FROM t1,t1 t2,t1 t3,t1 t4,t1 t5,t1 t6;
 SELECT * FROM t1 ORDER BY f LIMIT 1;
 DROP TABLE t1;
 SET sort_buffer_size=DEFAULT;
+
+--echo #
+--echo # BUG#11758979 - 51252: ARCHIVE TABLES CAUSE 100% CPU USAGE
+--echo #                       AND HANG IN SHOW TABLE STATUS
+--echo # (to be executed with valgrind)
+CREATE TABLE t1(a BLOB, b VARCHAR(200)) ENGINE=ARCHIVE;
+INSERT INTO t1 VALUES(NULL, '');
+FLUSH TABLE t1;
+--echo # we need this select to workaround BUG#11764364
+SELECT * FROM t1;
+CHECKSUM TABLE t1 EXTENDED;
+FLUSH TABLE t1;
+OPTIMIZE TABLE t1;
+DROP TABLE t1;

storage/archive/ha_archive.cc

@@ -760,6 +760,7 @@ uint32 ha_archive::max_row_length(const uchar *buf)
        ptr != end ;
        ptr++)
   {
+    if (!table->field[*ptr]->is_null())
       length += 2 + ((Field_blob*)table->field[*ptr])->get_length();
   }
 
@@ -1110,6 +1111,17 @@ int ha_archive::unpack_row(azio_stream *file_to_read, uchar *record)
 
   /* Copy null bits */
   const uchar *ptr= record_buffer->buffer;
+  /*
+    Field::unpack() is not called when field is NULL. For VARCHAR
+    Field::unpack() only unpacks as much bytes as occupied by field
+    value. In these cases respective memory area on record buffer is
+    not initialized.
+
+    These uninitialized areas may be accessed by CHECKSUM TABLE or
+    by optimizer using temporary table (BUG#12997905). We may remove
+    this memset() when they're fixed.
+  */
+  memset(record, 0, table->s->reclength);
   memcpy(record, ptr, table->s->null_bytes);
   ptr+= table->s->null_bytes;
   for (Field **field=table->field ; *field ; field++)
@@ -1578,13 +1590,15 @@ int ha_archive::check(THD* thd, HA_CHECK_OPT* check_opt)
 {
   int rc= 0;
   const char *old_proc_info;
-  ha_rows count= share->rows_recorded;
+  ha_rows count;
   DBUG_ENTER("ha_archive::check");
 
   old_proc_info= thd_proc_info(thd, "Checking table");
-  /* Flush any waiting data */
   pthread_mutex_lock(&share->mutex);
-  azflush(&(share->archive_write), Z_SYNC_FLUSH);
+  count= share->rows_recorded;
+  /* Flush any waiting data */
+  if (share->archive_write_open)
+    azflush(&(share->archive_write), Z_SYNC_FLUSH);
   pthread_mutex_unlock(&share->mutex);
 
   if (init_archive_reader())
@@ -1594,18 +1608,34 @@ int ha_archive::check(THD* thd, HA_CHECK_OPT* check_opt)
     start of the file.
   */
   read_data_header(&archive);
+  for (ha_rows cur_count= count; cur_count; cur_count--)
+  {
+    if ((rc= get_row(&archive, table->record[0])))
+      goto error;
+  }
+  /*
+    Now read records that may have been inserted concurrently.
+    Acquire share->mutex so tail of the table is not modified by
+    concurrent writers.
+  */
+  pthread_mutex_lock(&share->mutex);
+  count= share->rows_recorded - count;
+  if (share->archive_write_open)
+    azflush(&(share->archive_write), Z_SYNC_FLUSH);
   while (!(rc= get_row(&archive, table->record[0])))
     count--;
-
-  thd_proc_info(thd, old_proc_info);
+  pthread_mutex_unlock(&share->mutex);
 
   if ((rc && rc != HA_ERR_END_OF_FILE) || count)  
-  {
-    share->crashed= FALSE;
-    DBUG_RETURN(HA_ADMIN_CORRUPT);
-  }
+    goto error;
 
+  thd_proc_info(thd, old_proc_info);
   DBUG_RETURN(HA_ADMIN_OK);
+
+error:
+  thd_proc_info(thd, old_proc_info);
+  share->crashed= FALSE;
+  DBUG_RETURN(HA_ADMIN_CORRUPT);
 }
 
 /*