1 files changed, 35 insertions, 16 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 64a2049a37b..bd6065c9403 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -1029,19 +1029,24 @@ get_datetime_value(THD *thd, Item ***item_arg, Item **cache_arg,
        1    if items are equal or both are null
        0    otherwise
     If is_nulls_eq is FALSE:
-      -1   a < b or one of items is null
+      -1   a < b or at least one item is null
        0   a == b
        1   a > b
+    See the table:
+    is_nulls_eq | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 |
+    a_is_null   | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 |
+    b_is_null   | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 |
+    result      | 1 | 0 | 0 |0/1|-1 |-1 |-1 |-1/0/1|
 */
 
 int Arg_comparator::compare_datetime()
 {
-  bool is_null= FALSE;
+  bool a_is_null, b_is_null;
   ulonglong a_value, b_value;
 
   /* Get DATE/DATETIME/TIME value of the 'a' item. */
-  a_value= (*get_value_func)(thd, &a, &a_cache, *b, &is_null);
-  if (!is_nulls_eq && is_null)
+  a_value= (*get_value_func)(thd, &a, &a_cache, *b, &a_is_null);
+  if (!is_nulls_eq && a_is_null)
   {
     if (owner)
       owner->null_value= 1;
@@ -1049,14 +1054,15 @@ int Arg_comparator::compare_datetime()
   }
 
   /* Get DATE/DATETIME/TIME value of the 'b' item. */
-  b_value= (*get_value_func)(thd, &b, &b_cache, *a, &is_null);
-  if (is_null)
+  b_value= (*get_value_func)(thd, &b, &b_cache, *a, &b_is_null);
+  if (a_is_null || b_is_null)
   {
     if (owner)
       owner->null_value= is_nulls_eq ? 0 : 1;
-    return is_nulls_eq ? 1 : -1;
+    return is_nulls_eq ? (a_is_null == b_is_null) : -1;
   }
 
+  /* Here we have two not-NULL values. */
   if (owner)
     owner->null_value= 0;
 
@@ -4460,8 +4466,20 @@ void Item_func_like::cleanup()
 
 #ifdef USE_REGEX
 
-bool
-Item_func_regex::regcomp(bool send_error)
+/**
+  @brief Compile regular expression.
+
+  @param[in]    send_error     send error message if any.
+
+  @details Make necessary character set conversion then 
+  compile regular expression passed in the args[1].
+
+  @retval    0     success.
+  @retval    1     error occurred.
+  @retval   -1     given null regular expression.
+ */
+
+int Item_func_regex::regcomp(bool send_error)
 {
   char buff[MAX_FIELD_WIDTH];
   String tmp(buff,sizeof(buff),&my_charset_bin);
@@ -4469,12 +4487,12 @@ Item_func_regex::regcomp(bool send_error)
   int error;
 
   if (args[1]->null_value)
-    return TRUE;
+    return -1;
 
   if (regex_compiled)
   {
     if (!stringcmp(res, &prev_regexp))
-      return FALSE;
+      return 0;
     prev_regexp.copy(*res);
     my_regfree(&preg);
     regex_compiled= 0;
@@ -4486,7 +4504,7 @@ Item_func_regex::regcomp(bool send_error)
     uint dummy_errors;
     if (conv.copy(res->ptr(), res->length(), res->charset(),
                   regex_lib_charset, &dummy_errors))
-      return TRUE;
+      return 1;
     res= &conv;
   }
 
@@ -4498,10 +4516,10 @@ Item_func_regex::regcomp(bool send_error)
       (void) my_regerror(error, &preg, buff, sizeof(buff));
       my_error(ER_REGEXP_ERROR, MYF(0), buff);
     }
-    return TRUE;
+    return 1;
   }
   regex_compiled= 1;
-  return FALSE;
+  return 0;
 }
 
 
@@ -4539,13 +4557,14 @@ Item_func_regex::fix_fields(THD *thd, Item **ref)
   const_item_cache=args[0]->const_item() && args[1]->const_item();
   if (!regex_compiled && args[1]->const_item())
   {
-    if (args[1]->null_value)
+    int comp_res= regcomp(TRUE);
+    if (comp_res == -1)
     {						// Will always return NULL
       maybe_null=1;
       fixed= 1;
       return FALSE;
     }
-    if (regcomp(TRUE))
+    else if (comp_res)
       return TRUE;
     regex_is_const= 1;
     maybe_null= args[0]->maybe_null;