Bug#31702 (Missing row on slave causes assertion failure under row-based replication):

When replicating an update pair (before image, after image) under row-based
replication, and the before image is not found on the slave, the after image
was not discared, and was hence read as a before image for the next row.
Eventually, this lead to an after image being read outside the block of rows
in the event, causing an assertion to fire.

This patch fixes this by reading the after image in the event that the row
was not found on the slave, adds some extra debug assertion to catch future
errors earlier, and also adds a few non-debug checks to prevent reading
outside the block of the event.

include/my_base.h

@@ -407,9 +407,11 @@ enum ha_base_keytype {
 #define HA_ERR_RECORD_IS_THE_SAME 169    /* row not actually updated : 
                                             new values same as the old values */
 
-#define HA_ERR_LOGGING_IMPOSSIBLE 170 /* It is not possible to log this
-                                         statement */
-#define HA_ERR_LAST              170 /*Copy last error nr.*/
+#define HA_ERR_LOGGING_IMPOSSIBLE 170    /* It is not possible to log this
+                                            statement */
+#define HA_ERR_CORRUPT_EVENT      171    /* The event was corrupt, leading to
+                                            illegal data being read */
+#define HA_ERR_LAST              171     /*Copy last error nr.*/
 /* Add error numbers before HA_ERR_LAST and change it accordingly. */
 #define HA_ERR_ERRORS            (HA_ERR_LAST - HA_ERR_FIRST + 1)
 

mysql-test/suite/rpl/r/rpl_row_basic_11bugs.result

@@ -242,3 +242,34 @@ a	b
 3	1
 4	4
 drop table t1,t2;
+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;
+**** On Master ****
+SET SESSION BINLOG_FORMAT=ROW;
+CREATE TABLE t1 (a INT PRIMARY KEY, b SET('master','slave'));
+INSERT INTO t1 VALUES (1,'master,slave'), (2,'master,slave');
+**** On Slave ****
+UPDATE t1 SET a = 5, b = 'slave' WHERE a = 1;
+SELECT * FROM t1 ORDER BY a;
+a	b
+2	master,slave
+5	slave
+**** On Master ****
+UPDATE t1 SET a = 5, b = 'master' WHERE a = 1;
+SELECT * FROM t1 ORDER BY a;
+a	b
+2	master,slave
+5	master
+**** On Slave ****
+Last_SQL_Error
+Error in Update_rows event: error during transaction execution on table test.t1. Can't find record in 't1'
+SELECT * FROM t1 ORDER BY a;
+a	b
+2	master,slave
+5	slave
+DROP TABLE t1;
+**** On Master ****
+DROP TABLE t1;

mysql-test/suite/rpl/t/rpl_row_basic_11bugs.test

@@ -223,3 +223,40 @@ connection master;
 drop table t1,t2;
 
 sync_slave_with_master;
+
+#
+# BUG#31702: Missing row on slave causes assertion failure under
+# row-based replication 
+#
+
+disable_query_log;
+source include/master-slave-reset.inc;
+enable_query_log;
+
+--echo **** On Master ****
+connection master;
+SET SESSION BINLOG_FORMAT=ROW;
+CREATE TABLE t1 (a INT PRIMARY KEY, b SET('master','slave'));
+INSERT INTO t1 VALUES (1,'master,slave'), (2,'master,slave');
+--echo **** On Slave ****
+sync_slave_with_master;
+UPDATE t1 SET a = 5, b = 'slave' WHERE a = 1;
+SELECT * FROM t1 ORDER BY a;
+--echo **** On Master ****
+connection master;
+UPDATE t1 SET a = 5, b = 'master' WHERE a = 1;
+save_master_pos;
+SELECT * FROM t1 ORDER BY a;
+--echo **** On Slave ****
+connection slave;
+source include/wait_for_slave_sql_error.inc;
+let $last_error = query_get_value("SHOW SLAVE STATUS", Last_SQL_Error, 1);
+disable_query_log;
+eval SELECT "$last_error" AS Last_SQL_Error;
+enable_query_log;
+SELECT * FROM t1 ORDER BY a;
+DROP TABLE t1;
+
+--echo **** On Master ****
+connection master;
+DROP TABLE t1;

sql/log_event.cc

@@ -6173,14 +6173,19 @@ int Rows_log_event::do_apply_event(Relay_log_info const *rli)
       table->in_use = old_thd;
       switch (error)
       {
-        /* Some recoverable errors */
-      case HA_ERR_RECORD_CHANGED:
-      case HA_ERR_KEY_NOT_FOUND:	/* Idempotency support: OK if
-                                           tuple does not exist */
-	error= 0;
       case 0:
 	break;
 
+      /* Some recoverable errors */
+      case HA_ERR_RECORD_CHANGED:
+      case HA_ERR_KEY_NOT_FOUND:	/* Idempotency support: OK if
+                                           tuple does not exist */
+        if (get_type_code() != UPDATE_ROWS_EVENT)
+        {
+          error= 0;
+          break;
+        }
+        /* Fall through in the event that we have an update event */
       default:
 	rli->report(ERROR_LEVEL, thd->net.last_errno,
                     "Error in %s event: row application failed. %s",
@@ -6197,6 +6202,10 @@ int Rows_log_event::do_apply_event(Relay_log_info const *rli)
        m_curr_row_end.
       */ 
    
+      DBUG_PRINT("info", ("error: %d", error));
+      DBUG_PRINT("info", ("curr_row: 0x%lu; curr_row_end: 0x%lu; rows_end: 0x%lu",
+                          (ulong) m_curr_row, (ulong) m_curr_row_end, (ulong) m_rows_end));
+
       if (!m_curr_row_end && !error)
         unpack_current_row(rli);
   
@@ -7931,7 +7940,15 @@ Update_rows_log_event::do_exec_row(const Relay_log_info *const rli)
 
   int error= find_row(rli); 
   if (error)
+  {
+    /*
+      We need to read the second image in the event of error to be
+      able to skip to the next pair of updates
+    */
+    m_curr_row= m_curr_row_end;
+    unpack_current_row(rli);
     return error;
+  }
 
   /*
     This is the situation after locating BI:

sql/log_event.h

@@ -37,6 +37,23 @@
 #include "rpl_reporting.h"
 #endif
 
+/**
+   Either assert or return an error.
+
+   In debug build, the condition will be checked, but in non-debug
+   builds, the error code given will be returned instead.
+
+   @param COND   Condition to check
+   @param ERRNO  Error number to return in non-debug builds
+*/
+#ifdef DBUG_OFF
+#define ASSERT_OR_RETURN_ERROR(COND, ERRNO) \
+  do { if (!(COND)) return ERRNO; } while (0)
+#else
+#define ASSERT_OR_RETURN_ERROR(COND, ERRNO) \
+  DBUG_ASSERT(COND)
+#endif
+
 #define LOG_READ_EOF    -1
 #define LOG_READ_BOGUS  -2
 #define LOG_READ_IO     -3
@@ -2316,8 +2333,11 @@ protected:
   int unpack_current_row(const Relay_log_info *const rli)
   { 
     DBUG_ASSERT(m_table);
-    return ::unpack_row(rli, m_table, m_width, m_curr_row, &m_cols, 
-                        &m_curr_row_end, &m_master_reclength);
+    ASSERT_OR_RETURN_ERROR(m_curr_row < m_rows_end, HA_ERR_CORRUPT_EVENT);
+    int const result= ::unpack_row(rli, m_table, m_width, m_curr_row, &m_cols,
+                                   &m_curr_row_end, &m_master_reclength);
+    ASSERT_OR_RETURN_ERROR(m_curr_row_end <= m_rows_end, HA_ERR_CORRUPT_EVENT);
+    return result;
   }
 #endif