1 files changed, 51 insertions, 2 deletions

diff --git a/sql/handler.cc b/sql/handler.cc
index 67f9e25703e..9c03a9ef88f 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -1492,6 +1492,46 @@ void handler::adjust_next_insert_id_after_explicit_value(ulonglong nr)
 
 
 /*
+  Computes the largest number X:
+  - smaller than or equal to "nr"
+  - of the form: auto_increment_offset + N * auto_increment_increment
+  where N>=0.
+
+  SYNOPSIS
+    prev_insert_id
+      nr            Number to "round down"
+      variables     variables struct containing auto_increment_increment and
+                    auto_increment_offset
+
+  RETURN
+    The number X if it exists, "nr" otherwise.
+*/
+
+inline ulonglong
+prev_insert_id(ulonglong nr, struct system_variables *variables)
+{
+  if (unlikely(nr < variables->auto_increment_offset))
+  {
+    /*
+      There's nothing good we can do here. That is a pathological case, where
+      the offset is larger than the column's max possible value, i.e. not even
+      the first sequence value may be inserted. User will receive warning.
+    */
+    DBUG_PRINT("info",("auto_increment: nr: %lu cannot honour "
+                       "auto_increment_offset: %lu",
+                       nr, variables->auto_increment_offset));
+    return nr;
+  }
+  if (variables->auto_increment_increment == 1)
+    return nr; // optimization of the formula below
+  nr= (((nr - variables->auto_increment_offset)) /
+       (ulonglong) variables->auto_increment_increment);
+  return (nr * (ulonglong) variables->auto_increment_increment +
+          variables->auto_increment_offset);
+}
+
+
+/*
   Update the auto_increment field if necessary
 
   SYNOPSIS
@@ -1590,10 +1630,19 @@ bool handler::update_auto_increment()
   /* Mark that we should clear next_insert_id before next stmt */
   thd->clear_next_insert_id= 1;
 
-  if (!table->next_number_field->store((longlong) nr, TRUE))
+  if (likely(!table->next_number_field->store((longlong) nr, TRUE)))
     thd->insert_id((ulonglong) nr);
   else
-    thd->insert_id(table->next_number_field->val_int());
+  {
+    /*
+      overflow of the field; we'll use the max value, however we try to
+      decrease it to honour auto_increment_* variables:
+    */
+    nr= prev_insert_id(table->next_number_field->val_int(), variables);
+    thd->insert_id(nr);
+    if (unlikely(table->next_number_field->store((longlong) nr, TRUE)))
+      thd->insert_id(nr= table->next_number_field->val_int());
+  }
 
   /*
     We can't set next_insert_id if the auto-increment key is not the