merge

mysql-test/include/partition_date_range.inc

+# Created for verifying bug#20577.
+# expects TABLE t1 (... , a DATE, ...)
+
+--sorted_result
+SELECT * FROM t1 WHERE a < '1001-01-01';
+--sorted_result
+SELECT * FROM t1 WHERE a <= '1001-01-01';
+--sorted_result
+SELECT * FROM t1 WHERE a >= '1001-01-01';
+--sorted_result
+SELECT * FROM t1 WHERE a > '1001-01-01';
+--sorted_result
+SELECT * FROM t1 WHERE a = '1001-01-01';
+--sorted_result
+SELECT * FROM t1 WHERE a < '1001-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a <= '1001-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a >= '1001-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a > '1001-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a = '1001-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a < '1999-02-31';
+--sorted_result
+SELECT * FROM t1 WHERE a <= '1999-02-31';
+--sorted_result
+SELECT * FROM t1 WHERE a >= '1999-02-31';
+--sorted_result
+SELECT * FROM t1 WHERE a > '1999-02-31';
+--sorted_result
+SELECT * FROM t1 WHERE a = '1999-02-31';
+--sorted_result
+SELECT * FROM t1 WHERE a BETWEEN '0000-00-00' AND '1002-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a BETWEEN '0000-00-00' AND '1001-01-01';
+--sorted_result
+SELECT * FROM t1 WHERE a BETWEEN '0001-01-02' AND '1002-00-00';
+--sorted_result
+SELECT * FROM t1 WHERE a BETWEEN '0001-01-01' AND '1001-01-01';
+if ($explain_partitions)
+{
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a < '1001-01-01';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a <= '1001-01-01';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a >= '1001-01-01';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a > '1001-01-01';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a = '1001-01-01';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a < '1001-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a <= '1001-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a >= '1001-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a > '1001-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a = '1001-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a < '1999-02-31';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a <= '1999-02-31';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a >= '1999-02-31';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a > '1999-02-31';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a = '1999-02-31';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a BETWEEN '0000-00-00' AND '1002-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a BETWEEN '0000-00-00' AND '1001-01-01';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a BETWEEN '0001-01-02' AND '1002-00-00';
+EXPLAIN PARTITIONS SELECT * FROM t1 WHERE a BETWEEN '0001-01-01' AND '1001-01-01';
+}

mysql-test/r/partition_range.result

@@ -745,7 +745,7 @@ a
 EXPLAIN PARTITIONS SELECT * FROM t1
 WHERE a >= '2004-07-01' AND a <= '2004-09-30';
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	p407,p408,p409	ALL	NULL	NULL	NULL	NULL	9	Using where
+1	SIMPLE	t1	p3xx,p407,p408,p409	ALL	NULL	NULL	NULL	NULL	18	Using where
 SELECT * from t1
 WHERE (a >= '2004-07-01' AND a <= '2004-09-30') OR
 (a >= '2005-07-01' AND a <= '2005-09-30');
@@ -772,7 +772,7 @@ EXPLAIN PARTITIONS SELECT * from t1
 WHERE (a >= '2004-07-01' AND a <= '2004-09-30') OR
 (a >= '2005-07-01' AND a <= '2005-09-30');
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	p407,p408,p409,p507,p508,p509	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t1	p3xx,p407,p408,p409,p507,p508,p509	ALL	NULL	NULL	NULL	NULL	27	Using where
 DROP TABLE t1;
 create table t1 (a int);
 insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

sql-common/my_time.c

@@ -450,9 +450,7 @@ str_to_datetime(const char *str, uint length, MYSQL_TIME *l_time,
     }
   }
 
-  DBUG_RETURN(l_time->time_type=
-              (number_of_fields <= 3 ? MYSQL_TIMESTAMP_DATE :
-                                       MYSQL_TIMESTAMP_DATETIME));
+  DBUG_RETURN(l_time->time_type);
 
 err:
   bzero((char*) l_time, sizeof(*l_time));

sql/item.cc

@@ -6853,14 +6853,21 @@ void resolve_const_item(THD *thd, Item **ref, Item *comp_item)
 }
 
 /**
-  Return true if the value stored in the field is equal to the const
-  item.
+  Compare the value stored in field, with the original item.
 
-  We need to use this on the range optimizer because in some cases
-  we can't store the value in the field without some precision/character loss.
+  @param field   field which the item is converted and stored in
+  @param item    original item
+
+  @return Return an integer greater than, equal to, or less than 0 if
+          the value stored in the field is greater than,  equal to,
+          or less than the original item
+
+  @note We only use this on the range optimizer/partition pruning,
+        because in some cases we can't store the value in the field
+        without some precision/character loss.
 */
 
-bool field_is_equal_to_item(Field *field,Item *item)
+int stored_field_cmp_to_item(Field *field, Item *item)
 {
 
   Item_result res_type=item_cmp_type(field->result_type(),
@@ -6871,28 +6878,49 @@ bool field_is_equal_to_item(Field *field,Item *item)
     char field_buff[MAX_FIELD_WIDTH];
     String item_tmp(item_buff,sizeof(item_buff),&my_charset_bin),*item_result;
     String field_tmp(field_buff,sizeof(field_buff),&my_charset_bin);
+    enum_field_types field_type;
     item_result=item->val_str(&item_tmp);
     if (item->null_value)
-      return 1;					// This must be true
+      return 0;
     field->val_str(&field_tmp);
-    return !stringcmp(&field_tmp,item_result);
+
+    /*
+      If comparing DATE with DATETIME, append the time-part to the DATE.
+      So that the strings are equally formatted.
+      A DATE converted to string is 10 characters, and a DATETIME converted
+      to string is 19 characters.
+    */
+    field_type= field->type();
+    if (field_type == MYSQL_TYPE_DATE &&
+        item_result->length() == 19)
+      field_tmp.append(" 00:00:00");
+    else if (field_type == MYSQL_TYPE_DATETIME &&
+             item_result->length() == 10)
+      item_result->append(" 00:00:00");
+
+    return stringcmp(&field_tmp,item_result);
   }
   if (res_type == INT_RESULT)
-    return 1;					// Both where of type int
+    return 0;					// Both are of type int
   if (res_type == DECIMAL_RESULT)
   {
     my_decimal item_buf, *item_val,
                field_buf, *field_val;
     item_val= item->val_decimal(&item_buf);
     if (item->null_value)
-      return 1;					// This must be true
+      return 0;
     field_val= field->val_decimal(&field_buf);
-    return !my_decimal_cmp(item_val, field_val);
+    return my_decimal_cmp(item_val, field_val);
   }
   double result= item->val_real();
   if (item->null_value)
+    return 0;
+  double field_result= field->val_real();
+  if (field_result < result)
+    return -1;
+  else if (field_result > result)
     return 1;
-  return result == field->val_real();
+  return 0;
 }
 
 Item_cache* Item_cache::get_cache(const Item *item)

sql/item.h

@@ -397,13 +397,20 @@ public:
   from INT_RESULT, may be NULL, or are unsigned.
   It will be possible to address this issue once the related partitioning bugs
   (BUG#16002, BUG#15447, BUG#13436) are fixed.
+
+  The NOT_NULL enums are used in TO_DAYS, since TO_DAYS('2001-00-00') returns
+  NULL which puts those rows into the NULL partition, but
+  '2000-12-31' < '2001-00-00' < '2001-01-01'. So special handling is needed
+  for this (see Bug#20577).
 */
 
 typedef enum monotonicity_info 
 {
    NON_MONOTONIC,              /* none of the below holds */
    MONOTONIC_INCREASING,       /* F() is unary and (x < y) => (F(x) <= F(y)) */
-   MONOTONIC_STRICT_INCREASING /* F() is unary and (x < y) => (F(x) <  F(y)) */
+   MONOTONIC_INCREASING_NOT_NULL,  /* But only for valid/real x and y */
+   MONOTONIC_STRICT_INCREASING,/* F() is unary and (x < y) => (F(x) <  F(y)) */
+   MONOTONIC_STRICT_INCREASING_NOT_NULL  /* But only for valid/real x and y */
 } enum_monotonicity_info;
 
 /*************************************************************************/
@@ -576,8 +583,8 @@ public:
         left_endp  FALSE  <=> The interval is "x < const" or "x <= const"
                    TRUE   <=> The interval is "x > const" or "x >= const"
 
-        incl_endp  IN   TRUE <=> the comparison is '<' or '>'
-                        FALSE <=> the comparison is '<=' or '>='
+        incl_endp  IN   FALSE <=> the comparison is '<' or '>'
+                        TRUE  <=> the comparison is '<=' or '>='
                    OUT  The same but for the "F(x) $CMP$ F(const)" comparison
 
     DESCRIPTION
@@ -3118,4 +3125,4 @@ void mark_select_range_as_dependent(THD *thd,
 extern Cached_item *new_Cached_item(THD *thd, Item *item);
 extern Item_result item_cmp_type(Item_result a,Item_result b);
 extern void resolve_const_item(THD *thd, Item **ref, Item *cmp_item);
-extern bool field_is_equal_to_item(Field *field,Item *item);
+extern int stored_field_cmp_to_item(Field *field, Item *item);

sql/item_timefunc.cc

@@ -960,9 +960,9 @@ enum_monotonicity_info Item_func_to_days::get_monotonicity_info() const
   if (args[0]->type() == Item::FIELD_ITEM)
   {
     if (args[0]->field_type() == MYSQL_TYPE_DATE)
-      return MONOTONIC_STRICT_INCREASING;
+      return MONOTONIC_STRICT_INCREASING_NOT_NULL;
     if (args[0]->field_type() == MYSQL_TYPE_DATETIME)
-      return MONOTONIC_INCREASING;
+      return MONOTONIC_INCREASING_NOT_NULL;
   }
   return NON_MONOTONIC;
 }
@@ -973,12 +973,27 @@ longlong Item_func_to_days::val_int_endpoint(bool left_endp, bool *incl_endp)
   DBUG_ASSERT(fixed == 1);
   MYSQL_TIME ltime;
   longlong res;
-  if (get_arg0_date(&ltime, TIME_NO_ZERO_DATE))
+  int dummy;                                /* unused */
+  if (get_arg0_date(&ltime, TIME_FUZZY_DATE))
   {
     /* got NULL, leave the incl_endp intact */
     return LONGLONG_MIN;
   }
   res=(longlong) calc_daynr(ltime.year,ltime.month,ltime.day);
+  /* Set to NULL if invalid date, but keep the value */
+  null_value= check_date(&ltime,
+                         (ltime.year || ltime.month || ltime.day),
+                         (TIME_NO_ZERO_IN_DATE | TIME_NO_ZERO_DATE),
+                         &dummy);
+  if (null_value)
+  {
+    /*
+      Even if the evaluation return NULL, the calc_daynr is useful for pruning
+    */
+    if (args[0]->field_type() != MYSQL_TYPE_DATE)
+      *incl_endp= TRUE;
+    return res;
+  }
   
   if (args[0]->field_type() == MYSQL_TYPE_DATE)
   {
@@ -991,15 +1006,19 @@ longlong Item_func_to_days::val_int_endpoint(bool left_endp, bool *incl_endp)
     point to day bound ("strictly less" comparison stays intact):
 
       col < '2007-09-15 00:00:00'  -> TO_DAYS(col) <  TO_DAYS('2007-09-15')
+      col > '2007-09-15 23:59:59'  -> TO_DAYS(col) >  TO_DAYS('2007-09-15')
 
     which is different from the general case ("strictly less" changes to
     "less or equal"):
 
       col < '2007-09-15 12:34:56'  -> TO_DAYS(col) <= TO_DAYS('2007-09-15')
   */
-  if (!left_endp && !(ltime.hour || ltime.minute || ltime.second ||
-                      ltime.second_part))
-    ; /* do nothing */
+  if ((!left_endp && !(ltime.hour || ltime.minute || ltime.second ||
+                       ltime.second_part)) ||
+       (left_endp && ltime.hour == 23 && ltime.minute == 59 &&
+        ltime.second == 59))
+    /* do nothing */
+    ;
   else
     *incl_endp= TRUE;
   return res;

sql/mysql_priv.h

@@ -2277,7 +2277,8 @@ enum enum_explain_filename_mode
 {
   EXPLAIN_ALL_VERBOSE= 0,
   EXPLAIN_PARTITIONS_VERBOSE,
-  EXPLAIN_PARTITIONS_AS_COMMENT
+  EXPLAIN_PARTITIONS_AS_COMMENT,
+  EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING
 };
 uint explain_filename(const char *from, char *to, uint to_length,
                       enum_explain_filename_mode explain_mode);

sql/opt_range.cc

@@ -5826,6 +5826,7 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
       {
         tree= new (alloc) SEL_ARG(field, 0, 0);
         tree->type= SEL_ARG::IMPOSSIBLE;
+        field->table->in_use->variables.sql_mode= orig_sql_mode;
         goto end;
       }
       else
@@ -5855,11 +5856,14 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
 
             but we'll need to convert '>' to '>=' and '<' to '<='. This will
             be done together with other types at the end of this function
-            (grep for field_is_equal_to_item)
+            (grep for stored_field_cmp_to_item)
           */
         }
         else
+        {
+          field->table->in_use->variables.sql_mode= orig_sql_mode;
           goto end;
+        }
       }
     }
 
@@ -5930,7 +5934,7 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
 
   switch (type) {
   case Item_func::LT_FUNC:
-    if (field_is_equal_to_item(field,value))
+    if (stored_field_cmp_to_item(field,value) == 0)
       tree->max_flag=NEAR_MAX;
     /* fall through */
   case Item_func::LE_FUNC:
@@ -5944,11 +5948,16 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
     break;
   case Item_func::GT_FUNC:
     /* Don't use open ranges for partial key_segments */
-    if (field_is_equal_to_item(field,value) &&
-        !(key_part->flag & HA_PART_KEY_SEG))
+    if ((!(key_part->flag & HA_PART_KEY_SEG)) &&
+        (stored_field_cmp_to_item(field, value) <= 0))
       tree->min_flag=NEAR_MIN;
-    /* fall through */
+    tree->max_flag= NO_MAX_RANGE;
+    break;
   case Item_func::GE_FUNC:
+    /* Don't use open ranges for partial key_segments */
+    if ((!(key_part->flag & HA_PART_KEY_SEG)) &&
+        (stored_field_cmp_to_item(field,value) < 0))
+      tree->min_flag= NEAR_MIN;
     tree->max_flag=NO_MAX_RANGE;
     break;
   case Item_func::SP_EQUALS_FUNC:
@@ -6439,13 +6448,6 @@ key_and(RANGE_OPT_PARAM *param, SEL_ARG *key1, SEL_ARG *key2, uint clone_flag)
     return 0;					// Can't optimize this
   }
 
-  if ((key1->min_flag | key2->min_flag) & GEOM_FLAG)
-  {
-    key1->free_tree();
-    key2->free_tree();
-    return 0;					// Can't optimize this
-  }
-
   key1->use_count--;
   key2->use_count--;
   SEL_ARG *e1=key1->first(), *e2=key2->first(), *new_tree=0;

sql/partition_info.h

@@ -300,6 +300,7 @@ static inline void init_single_partition_iterator(uint32 part_id,
 {
   part_iter->part_nums.start= part_iter->part_nums.cur= part_id;
   part_iter->part_nums.end= part_id+1;
+  part_iter->ret_null_part= part_iter->ret_null_part_orig= FALSE;
   part_iter->get_next= get_next_partition_id_range;
 }
 

sql/share/errmsg.txt

@@ -6184,17 +6184,17 @@ ER_FUNC_INEXISTENT_NAME_COLLISION 42000
 # When updating these, please update EXPLAIN_FILENAME_MAX_EXTRA_LENGTH in
 # mysql_priv.h with the new maximal additional length for explain_filename.
 ER_DATABASE_NAME
-  eng "Database `%s`"
-  swe "Databas `%s`"
+  eng "Database"
+  swe "Databas"
 ER_TABLE_NAME
-  eng "Table `%s`"
-  swe "Tabell `%s`"
+  eng "Table"
+  swe "Tabell"
 ER_PARTITION_NAME
-  eng "Partition `%s`"
-  swe "Partition `%s`"
+  eng "Partition"
+  swe "Partition"
 ER_SUBPARTITION_NAME
-  eng "Subpartition `%s`"
-  swe "Subpartition `%s`"
+  eng "Subpartition"
+  swe "Subpartition"
 ER_TEMPORARY_NAME
   eng "Temporary"
   swe "Temporr"

sql/sql_partition.cc

@@ -2766,8 +2766,24 @@ uint32 get_list_array_idx_for_endpoint(partition_info *part_info,
 
   if (part_info->part_expr->null_value)
   {
-    DBUG_RETURN(0);
+    /*
+      Special handling for MONOTONIC functions that can return NULL for
+      values that are comparable. I.e.
+      '2000-00-00' can be compared to '2000-01-01' but TO_DAYS('2000-00-00')
+      returns NULL which cannot be compared used <, >, <=, >= etc.
+
+      Otherwise, just return the the first index (lowest value).
+    */
+    enum_monotonicity_info monotonic;
+    monotonic= part_info->part_expr->get_monotonicity_info();
+    if (monotonic != MONOTONIC_INCREASING_NOT_NULL && 
+        monotonic != MONOTONIC_STRICT_INCREASING_NOT_NULL)
+    {
+      /* F(col) can not return NULL, return index with lowest value */
+      DBUG_RETURN(0);
+    }
   }
+
   if (unsigned_flag)
     part_func_value-= 0x8000000000000000ULL;
   DBUG_ASSERT(part_info->no_list_values);
@@ -2916,11 +2932,29 @@ uint32 get_partition_id_range_for_endpoint(partition_info *part_info,
 
   if (part_info->part_expr->null_value)
   {
-    uint32 ret_part_id= 0;
-    if (!left_endpoint && include_endpoint)
-      ret_part_id= 1;
-    DBUG_RETURN(ret_part_id);
+    /*
+      Special handling for MONOTONIC functions that can return NULL for
+      values that are comparable. I.e.
+      '2000-00-00' can be compared to '2000-01-01' but TO_DAYS('2000-00-00')
+      returns NULL which cannot be compared used <, >, <=, >= etc.
+
+      Otherwise, just return the first partition
+      (may be included if not left endpoint)
+    */
+    enum_monotonicity_info monotonic;
+    monotonic= part_info->part_expr->get_monotonicity_info();
+    if (monotonic != MONOTONIC_INCREASING_NOT_NULL &&
+        monotonic != MONOTONIC_STRICT_INCREASING_NOT_NULL)
+    {
+      /* F(col) can not return NULL, return partition with lowest value */
+      if (!left_endpoint && include_endpoint)
+        DBUG_RETURN(1);
+      DBUG_RETURN(0);               
+
+    }
   }
+
+
   if (unsigned_flag)
     part_func_value-= 0x8000000000000000ULL;
   if (left_endpoint && !include_endpoint)
@@ -6696,6 +6730,7 @@ int get_part_iter_for_interval_via_mapping(partition_info *part_info,
   Field *field= part_info->part_field_array[0];
   uint32             max_endpoint_val;
   get_endpoint_func  get_endpoint;
+  bool               can_match_multiple_values;  /* is not '=' */
   uint field_len= field->pack_length_in_rec();
   part_iter->ret_null_part= part_iter->ret_null_part_orig= FALSE;
 
@@ -6733,6 +6768,23 @@ int get_part_iter_for_interval_via_mapping(partition_info *part_info,
   }
   else
     assert(0);
+  
+  can_match_multiple_values= (flags || !min_value || !max_value ||
+                              memcmp(min_value, max_value, field_len));
+  if (can_match_multiple_values &&
+      (part_info->part_type == RANGE_PARTITION ||
+       part_info->has_null_value))
+  {
+    /* Range scan on RANGE or LIST partitioned table */
+    enum_monotonicity_info monotonic;
+    monotonic= part_info->part_expr->get_monotonicity_info();
+    if (monotonic == MONOTONIC_INCREASING_NOT_NULL ||
+        monotonic == MONOTONIC_STRICT_INCREASING_NOT_NULL)
+    {
+      /* col is NOT NULL, but F(col) can return NULL, add NULL partition */
+      part_iter->ret_null_part= part_iter->ret_null_part_orig= TRUE;
+    }
+  }
 
   /* 
     Find minimum: Do special handling if the interval has left bound in form
@@ -6765,6 +6817,14 @@ int get_part_iter_for_interval_via_mapping(partition_info *part_info,
       store_key_image_to_rec(field, min_value, field_len);
       bool include_endp= !test(flags & NEAR_MIN);
       part_iter->part_nums.start= get_endpoint(part_info, 1, include_endp);
+      if (!can_match_multiple_values && part_info->part_expr->null_value)
+      {
+        /* col = x and F(x) = NULL -> only search NULL partition */
+        part_iter->part_nums.cur= part_iter->part_nums.start= 0;
+        part_iter->part_nums.end= 0;
+        part_iter->ret_null_part= part_iter->ret_null_part_orig= TRUE;
+        return 1;
+      }
       part_iter->part_nums.cur= part_iter->part_nums.start;
       if (part_iter->part_nums.start == max_endpoint_val)
         return 0; /* No partitions */
@@ -6959,7 +7019,13 @@ uint32 get_next_partition_id_range(PARTITION_ITERATOR* part_iter)
 {
   if (part_iter->part_nums.cur >= part_iter->part_nums.end)
   {
+    if (part_iter->ret_null_part)
+    {
+      part_iter->ret_null_part= FALSE;
+      return 0;                    /* NULL always in first range partition */
+    }
     part_iter->part_nums.cur= part_iter->part_nums.start;
+    part_iter->ret_null_part= part_iter->ret_null_part_orig;
     return NOT_A_PARTITION_ID;
   }
   else
@@ -6987,7 +7053,7 @@ uint32 get_next_partition_id_range(PARTITION_ITERATOR* part_iter)
 
 uint32 get_next_partition_id_list(PARTITION_ITERATOR *part_iter)
 {
-  if (part_iter->part_nums.cur == part_iter->part_nums.end)
+  if (part_iter->part_nums.cur >= part_iter->part_nums.end)
   {
     if (part_iter->ret_null_part)
     {

sql/sql_table.cc

@@ -72,7 +72,7 @@ static void wait_for_kill_signal(THD *thd)
   @brief Helper function for explain_filename
 */
 static char* add_identifier(char *to_p, const char * end_p,
-                           const char* name, uint name_len, int errcode)
+                           const char* name, uint name_len, bool add_quotes)
 {
   uint res;
   uint errors;
@@ -92,18 +92,44 @@ static char* add_identifier(char *to_p, const char * end_p,
   res= strconvert(&my_charset_filename, conv_name, system_charset_info,
                   conv_string, FN_REFLEN, &errors);
   if (!res || errors)
+  {
+    DBUG_PRINT("error", ("strconvert of '%s' failed with %u (errors: %u)", conv_name, res, errors));
     conv_name= name;
+  }
   else
   {
     DBUG_PRINT("info", ("conv '%s' -> '%s'", conv_name, conv_string));
     conv_name= conv_string;
   }
 
-  if (errcode)
-    to_p+= my_snprintf(to_p, end_p - to_p, ER(errcode), conv_name);
+  if (add_quotes && (end_p - to_p > 2))
+  {
+    *(to_p++)= '`';
+    while (*conv_name && (end_p - to_p - 1) > 0)
+    {
+      uint length= my_mbcharlen(system_charset_info, *conv_name);
+      if (!length)
+        length= 1;
+      if (length == 1 && *conv_name == '`')
+      { 
+        if ((end_p - to_p) < 3)
+          break;
+        *(to_p++)= '`';
+        *(to_p++)= *(conv_name++);
+      }
+      else if (length < (end_p - to_p))
+      {
+        to_p= strnmov(to_p, conv_name, length);
+        conv_name+= length;
+      }
+      else
+        break;                               /* string already filled */
+    }
+    to_p= strnmov(to_p, "`", end_p - to_p);
+  }
   else
-    to_p+= my_snprintf(to_p, end_p - to_p, "`%s`", conv_name);
-  return to_p;
+    to_p= strnmov(to_p, conv_name, end_p - to_p);
+  DBUG_RETURN(to_p);
 }
 
 
@@ -135,6 +161,8 @@ static char* add_identifier(char *to_p, const char * end_p,
                             [,[ Temporary| Renamed] Partition `p`
                             [, Subpartition `sp`]] *|
                             (| is really a /, and it is all in one line)
+                            EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING ->
+                            same as above but no quotes are added.
 
    @retval     Length of returned string
 */
@@ -245,28 +273,39 @@ uint explain_filename(const char *from,
         part_name_len-= 5;
     }
   }
+  else
+    table_name_len= strlen(table_name);
   if (db_name)
   {
     if (explain_mode == EXPLAIN_ALL_VERBOSE)
     {
-      to_p= add_identifier(to_p, end_p, db_name, db_name_len,
-                           ER_DATABASE_NAME);
+      to_p= strnmov(to_p, ER(ER_DATABASE_NAME), end_p - to_p);
+      *(to_p++)= ' ';
+      to_p= add_identifier(to_p, end_p, db_name, db_name_len, 1);
       to_p= strnmov(to_p, ", ", end_p - to_p);
     }
     else
     {
-      to_p= add_identifier(to_p, end_p, db_name, db_name_len, 0);
+      to_p= add_identifier(to_p, end_p, db_name, db_name_len,
+                           (explain_mode !=
+                            EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING));
       to_p= strnmov(to_p, ".", end_p - to_p);
     }
   }
   if (explain_mode == EXPLAIN_ALL_VERBOSE)
-    to_p= add_identifier(to_p, end_p, table_name, table_name_len,
-                         ER_TABLE_NAME);
+  {
+    to_p= strnmov(to_p, ER(ER_TABLE_NAME), end_p - to_p);
+    *(to_p++)= ' ';
+    to_p= add_identifier(to_p, end_p, table_name, table_name_len, 1);
+  }
   else
-    to_p= add_identifier(to_p, end_p, table_name, table_name_len, 0);
+    to_p= add_identifier(to_p, end_p, table_name, table_name_len,
+                         (explain_mode !=
+                          EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING));
   if (part_name)
   {
-    if (explain_mode == EXPLAIN_PARTITIONS_AS_COMMENT)
+    if (explain_mode == EXPLAIN_PARTITIONS_AS_COMMENT ||
+        explain_mode == EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING)
       to_p= strnmov(to_p, " /* ", end_p - to_p);
     else if (explain_mode == EXPLAIN_PARTITIONS_VERBOSE)
       to_p= strnmov(to_p, " ", end_p - to_p);
@@ -280,15 +319,22 @@ uint explain_filename(const char *from,
         to_p= strnmov(to_p, ER(ER_RENAMED_NAME), end_p - to_p);
       to_p= strnmov(to_p, " ", end_p - to_p);
     }
+    to_p= strnmov(to_p, ER(ER_PARTITION_NAME), end_p - to_p);
+    *(to_p++)= ' ';
     to_p= add_identifier(to_p, end_p, part_name, part_name_len,
-                         ER_PARTITION_NAME);
+                         (explain_mode !=
+                          EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING));
     if (subpart_name)
     {
       to_p= strnmov(to_p, ", ", end_p - to_p);
+      to_p= strnmov(to_p, ER(ER_SUBPARTITION_NAME), end_p - to_p);
+      *(to_p++)= ' ';
       to_p= add_identifier(to_p, end_p, subpart_name, subpart_name_len,
-                           ER_SUBPARTITION_NAME);
+                           (explain_mode !=
+                            EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING));
     }
-    if (explain_mode == EXPLAIN_PARTITIONS_AS_COMMENT)
+    if (explain_mode == EXPLAIN_PARTITIONS_AS_COMMENT ||
+        explain_mode == EXPLAIN_PARTITIONS_AS_COMMENT_NO_QUOTING)
       to_p= strnmov(to_p, " */", end_p - to_p);
   }
   DBUG_PRINT("exit", ("to '%s'", to));