Commit f8bb8923 authored by unknown's avatar unknown
Browse files

Fix for BUG#9622: Make index statistics collection in MyISAM behave the same 

way in ALTER TABLE ... ENABLE KEYS, ANALYZE TABLE and after bulk insert:
now statistics collection always assumes NULLs are inequal. 


mysql-test/r/myisam.result:
  Testcase for BUG#9622
mysql-test/t/myisam.test:
  Testcase for BUG#9622
parent 1fb790d3

myisam/mi_check.c

+35 −1
Original line number Diff line number Diff line
@@ -3243,6 +3243,9 @@ static int sort_key_write(MI_SORT_PARAM *sort_param, const void *a) 
    cmp=ha_key_cmp(sort_param->seg,sort_info->key_block->lastkey,

		   (uchar*) a, USE_WHOLE_KEY,SEARCH_FIND | SEARCH_UPDATE,

		   &diff_pos);

    ha_key_cmp(sort_param->seg,sort_info->key_block->lastkey,

               (uchar*) a, USE_WHOLE_KEY,SEARCH_FIND | SEARCH_NULL_ARE_NOT_EQUAL,

               &diff_pos);

    sort_param->unique[diff_pos-1]++;

  }

  else
@@ -3955,7 +3958,38 @@ void update_auto_increment_key(MI_CHECK *param, MI_INFO *info, 
  return;

}



    /* calculate unique keys for each part key */



/*

  Update statistics for each part of an index

  

  SYNOPSIS

    update_key_parts()

      keyinfo               Index information (only key->keysegs used)

      rec_per_key_part  OUT Store statistics here

      unique            IN  Array of #distinct values collected over index

                            run.

      records               Number of records in the table

      

  NOTES

    Unique is an array:

    unique[0]= (#different values of {keypart1}) - 1

    unique[1]= (#different values of {keypart2,keypart1} tuple) - unique[0] - 1

    ...

    Here we assume that NULL != NULL (see SEARCH_NULL_ARE_NOT_EQUAL). The

    'unique' array is collected in one sequential scan through the entire

    index. This is done in two places: in chk_index() and in sort_key_write().



    Output is an array:

    rec_per_key_part[k] = 

     = E(#records in the table such that keypart_1=c_1 AND ... AND 

         keypart_k=c_k for arbitrary constants c_1 ... c_k) 

     

     = {assuming that values have uniform distribution and index contains all

        tuples from the domain (or that {c_1, ..., c_k} tuple is choosen from

        index tuples}

     

     = #tuples-in-the-index / #distinct-tuples-in-the-index.

*/



void update_key_parts(MI_KEYDEF *keyinfo, ulong *rec_per_key_part,

			     ulonglong *unique, ulonglong records)

mysql-test/r/myisam.result

+14 −0
Original line number Diff line number Diff line
@@ -581,3 +581,17 @@ check table t1; 
Table	Op	Msg_type	Msg_text

test.t1	check	status	OK

drop table t1;

create table t1 (a int, key(a));

insert into t1 values (1),(2),(3),(4),(NULL),(NULL),(NULL),(NULL);

analyze table t1;

Table	Op	Msg_type	Msg_text

test.t1	analyze	status	OK

show keys from t1;

Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment

t1	1	a	1	a	A	8	NULL	NULL	YES	BTREE	

alter table t1 disable keys;

alter table t1 enable keys;

show keys from t1;

Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment

t1	1	a	1	a	A	8	NULL	NULL	YES	BTREE	

drop table t1;

mysql-test/t/myisam.test

+15 −0
Original line number Diff line number Diff line
@@ -560,3 +560,18 @@ update t1 set c2='A B' where c1=2; 
check table t1;

drop table t1;





# BUG#9622 - ANALYZE TABLE and ALTER TABLE .. ENABLE INDEX produce

# different statistics on the same table with NULL values.

create table t1 (a int, key(a));



insert into t1 values (1),(2),(3),(4),(NULL),(NULL),(NULL),(NULL);

analyze table t1;

show keys from t1;



alter table t1 disable keys;

alter table t1 enable keys;

show keys from t1;



drop table t1;