Bug #12752572 61579: REPLICATION FAILURE WHILE

INNODB_AUTOINC_LOCK_MODE=1 AND USING TRIGGER

When an insert stmt like "insert into t values (1),(2),(3)" is
executed, the autoincrement values assigned to these three rows are
expected to be contiguous.  In the given lock mode
(innodb_autoinc_lock_mode=1), the auto inc lock will be released
before the end of the statement.  So to make the autoincrement
contiguous for a given statement, we need to reserve the auto inc
values at the beginning of the statement.  

Modified the fix based on review comment by Svoj.  

sql/handler.cc

@@ -2398,18 +2398,18 @@ int handler::update_auto_increment()
         Note that in prelocked mode no estimation is given.
       */
 
-      /*
-        For multi-row inserts, if the bulk inserts cannot be started, the
-        handler::estimation_rows_to_insert will not be set. Set it here.
-      */
-      if ((estimation_rows_to_insert == 0) &&
-          (thd->lex->many_values.elements > 0))
-      {
-        estimation_rows_to_insert= thd->lex->many_values.elements;
-      }
-
       if ((auto_inc_intervals_count == 0) && (estimation_rows_to_insert > 0))
         nb_desired_values= estimation_rows_to_insert;
+      else if ((auto_inc_intervals_count == 0) &&
+               (thd->lex->many_values.elements > 0))
+      {
+        /*
+          For multi-row inserts, if the bulk inserts cannot be started, the
+          handler::estimation_rows_to_insert will not be set. But we still
+          want to reserve the autoinc values.
+        */
+        nb_desired_values= thd->lex->many_values.elements;
+      }
       else /* go with the increasing defaults */
       {
         /* avoid overflow in formula, with this if() */