BUG#47312: RBR: Disabling key on slave breaks replication:

HA_ERR_WRONG_INDEX
      
In RBR, disabling keys on slave table will break replication when
updating or deleting a record. When the slave thread tries to
find the row, by searching in the storage engine, it checks
whether the table has a key or not. If it has one, then the slave
thread uses it to search the record.
      
Nonetheless, the slave only checks whether the key exists or not,
it does not verify if it is active. Should the key be
disabled (eg, DBA has issued an ALTER TABLE ... DISABLE KEYS)
then it will result in error: HA_ERR_WRONG_INDEX.
      
This patch addresses this issue by making the slave thread also
check whether the key is active or not before actually using it.

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

+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;
+SET SQL_LOG_BIN=0;
+CREATE TABLE t (a int, b int, c int, key(b));
+SET SQL_LOG_BIN=1;
+CREATE TABLE t (a int, b int, c int);
+INSERT INTO t VALUES (1,2,4);
+INSERT INTO t VALUES (4,3,4);
+DELETE FROM t;
+DROP TABLE t;
+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;
+CREATE TABLE t (a int, b int, c int, key(b));
+ALTER TABLE t DISABLE KEYS;
+INSERT INTO t VALUES (1,2,4);
+INSERT INTO t VALUES (4,3,4);
+DELETE FROM t;
+DROP TABLE t;

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

+# BUG#47312: RBR: Disabling key on slave breaks replication:
+# HA_ERR_WRONG_INDEX
+#
+# Description
+# ===========
+#   
+#   This test case checks whether disabling a key on a slave breaks
+#   replication or not.
+#   
+#   Case #1, shows that while not using ALTER TABLE... DISABLE KEYS and
+#   the slave has no key defined while the master has one, replication
+#   won't break.
+#
+#   Case #2, shows that before patch for BUG#47312, if defining key on
+#   slave table, and later disable it, replication would break. This
+#   has been fixed.
+# 
+
+-- source include/master-slave.inc
+-- source include/have_binlog_format_row.inc
+
+#
+# Case #1: master has key, but slave has not. 
+#          Replication does not break.
+# 
+
+SET SQL_LOG_BIN=0;
+CREATE TABLE t (a int, b int, c int, key(b));
+SET SQL_LOG_BIN=1;
+
+-- connection slave
+
+CREATE TABLE t (a int, b int, c int);
+
+-- connection master
+
+INSERT INTO t VALUES (1,2,4);
+INSERT INTO t VALUES (4,3,4);
+DELETE FROM t;
+
+-- sync_slave_with_master
+
+-- connection master
+DROP TABLE t;
+
+-- sync_slave_with_master
+
+#
+# Case #2: master has key, slave also has one, 
+#          but it gets disabled sometime.
+#          Replication does not break anymore.
+# 
+-- source include/master-slave-reset.inc
+-- connection master
+
+CREATE TABLE t (a int, b int, c int, key(b));
+
+-- sync_slave_with_master
+
+ALTER TABLE t DISABLE KEYS;
+
+-- connection master
+
+INSERT INTO t VALUES (1,2,4);
+INSERT INTO t VALUES (4,3,4);
+DELETE FROM t;
+
+-- sync_slave_with_master
+
+-- connection master
+DROP TABLE t;
+
+-- sync_slave_with_master

sql/log_event.cc

@@ -8835,11 +8835,11 @@ int Rows_log_event::find_row(const Relay_log_info *rli)
    */ 
   store_record(table,record[1]);    
 
-  if (table->s->keys > 0)
+  if (table->s->keys > 0 && table->s->keys_in_use.is_set(0))
   {
     DBUG_PRINT("info",("locating record using primary key (index_read)"));
 
-    /* We have a key: search the table using the index */
+    /* The 0th key is active: search the table using the index */
     if (!table->file->inited && (error= table->file->ha_index_init(0, FALSE)))
     {
       DBUG_PRINT("info",("ha_index_init returns error %d",error));