Commit 072cca77 authored by sasha@mysql.sashanet.com's avatar sasha@mysql.sashanet.com
Browse files

handle tree overflow in count(distinct) 

test heap table/tree overflow in count(distinct)
parent ac379c40

mysql-test/r/count_distinct2.result

+8 −0
Original line number Diff line number Diff line
@@ -74,3 +74,11 @@ count(distinct n2) n1 
1	NULL

1	1

3	2

count(distinct n)

5000

Variable_name	Value

Created_tmp_disk_tables	1

count(distinct s)

5000

Variable_name	Value

Created_tmp_disk_tables	1

mysql-test/t/count_distinct2-master.opt

0 → 100644
+1 −0
Original line number Diff line number Diff line 
-O max_heap_table_size=16384

mysql-test/t/count_distinct2.test

+29 −0
Original line number Diff line number Diff line
@@ -43,3 +43,32 @@ select count(distinct n1), count(distinct n2) from t1; 


select count(distinct n2), n1 from t1 group by n1;

drop table t1;



# test the converstion from tree to MyISAM

create table t1 (n int);

let $1=5000;

while ($1)

{

 eval insert into t1 values($1);

 dec $1;

}



flush status;

select count(distinct n) from t1;

show status like 'Created_tmp_disk_tables';

drop table t1;



#test conversion from heap to MyISAM

create table t1 (s text);

let $1=5000;

while ($1)

{

 eval insert into t1 values('$1');

 dec $1;

}



flush status;

select count(distinct s) from t1;

show status like 'Created_tmp_disk_tables';

drop table t1;

sql/item_sum.cc

+42 −1
Original line number Diff line number Diff line
@@ -830,7 +830,26 @@ int composite_key_cmp(void* arg, byte* key1, byte* key2) 
  return 0;

}



// helper function for walking the tree when we dump it to MyISAM -

// tree_walk will call it for each

// leaf



int dump_leaf(byte* key, uint32 count __attribute__((unused)),

		     Item_sum_count_distinct* item)

{

  char* buf = item->table->record[0];

  int error;

  memset(buf, 0xff, item->rec_offset); // make up for cheating in the tree

  memcpy(buf + item->rec_offset, key, item->tree.size_of_element);

  if ((error = item->table->file->write_row(buf)))

  {

        if (error != HA_ERR_FOUND_DUPP_KEY &&

	    error != HA_ERR_FOUND_DUPP_UNIQUE)

	  return 1;

  }



  return 0;

}



Item_sum_count_distinct::~Item_sum_count_distinct()

{
@@ -916,11 +935,29 @@ bool Item_sum_count_distinct::setup(THD *thd) 
		key_len, compare_key, 0, 0);

      tree.cmp_arg = cmp_arg;

      use_tree = 1;



      // the only time key_len could be 0 is if someone does

      // count(distinct) on a char(0) field - stupid thing to do,

      // but this has to be handled - otherwise someone can crash

      // the server with a DoS attack

      max_elements_in_tree = (key_len) ? max_heap_table_size/key_len :

	max_heap_table_size;

    }

  

  return 0;

}



int Item_sum_count_distinct::tree_to_myisam()

{

  if(create_myisam_from_heap(table, tmp_table_param,

			     HA_ERR_RECORD_FILE_FULL, 1) ||

     tree_walk(&tree, (tree_walk_action)&dump_leaf, (void*)this,

	       left_root_right))

    return 1;

  delete_tree(&tree);

  use_tree = 0;

  return 0;

}



void Item_sum_count_distinct::reset()

{
@@ -947,7 +984,11 @@ bool Item_sum_count_distinct::add() 


  if(use_tree)

    {

      if(!tree_insert(&tree, table->record[0] + rec_offset, 0))

      // if the tree got too big, convert to MyISAM, otherwise

      // insert into the tree

      if((tree.elements_in_tree > max_elements_in_tree && tree_to_myisam())

	 ||

	 !tree_insert(&tree, table->record[0] + rec_offset, 0))

	return 1;

    }

  else if ((error=table->file->write_row(table->record[0])))

sql/item_sum.h

+14 −3
Original line number Diff line number Diff line
@@ -148,14 +148,25 @@ class Item_sum_count_distinct :public Item_sum_int 
  bool fix_fields(THD *thd,TABLE_LIST *tables);

  TMP_TABLE_PARAM *tmp_table_param;

  TREE tree;

  bool use_tree; // If there are no blobs, we can use a tree, which

  uint max_elements_in_tree;

  // calculated based on max_heap_table_size. If reached,

  // walk the tree and dump it into MyISAM table

  

  bool use_tree;

  // If there are no blobs, we can use a tree, which

  // is faster than heap table. In that case, we still use the table

  // to help get things set up, but we insert nothing in it

  int rec_offset; // the first few bytes of record ( at least one)

  

  int rec_offset;

  // the first few bytes of record ( at least one)

  // are just markers for deleted and NULLs. We want to skip them since

  // they will just bloat the tree without providing any valuable info



  int tree_to_myisam();

  

  friend int composite_key_cmp(void* arg, byte* key1, byte* key2);

  friend int dump_leaf(byte* key, uint32 count __attribute__((unused)),

		Item_sum_count_distinct* item);



  public:

  Item_sum_count_distinct(List<Item> &list)