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Added thread variable max_seeks_for_key

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Change optimizer to prefer key lookups before table scan
Change table scans to be done after tables with constrains on scanned table 


mysql-test/r/distinct.result:
  Update results
mysql-test/r/group_by.result:
  Update results
mysql-test/r/heap.result:
  Update results
mysql-test/r/join.result:
  Update results
mysql-test/r/key_diff.result:
  Update results
mysql-test/r/myisam.result:
  Update results
mysql-test/r/order_by.result:
  Update results
mysql-test/r/select_safe.result:
  Update results
mysql-test/t/distinct.test:
  Change test to be repeatable
mysql-test/t/join.test:
  Change test to be repeatable
mysql-test/t/select_safe.test:
  Add tests for MAX_SEEKS_FOR_KEY
sql/handler.h:
  Optimize structure for 64 bit machines (and to avoid problems with gdb)
sql/item_cmpfunc.cc:
  Initialize not_null_tables_cache properly
sql/mysqld.cc:
  Added max_seeks_for_key
sql/set_var.cc:
  Added max_seeks_for_key
sql/sql_class.h:
  Added max_seeks_for_key
sql/sql_select.cc:
  Added max_seeks_for_key
  Change optimizer to prefer key lookups before table scan.
  Change table scans to be done after tables with constrains on scanned table
This commit is contained in:
unknown
2003-06-27 03:04:54 +03:00
parent 7539980eb1
commit c2cb9b97be
17 changed files with 114 additions and 65 deletions
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41
sql/sql_select.cc
View File

@ -1271,14 +1271,14 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds,
/*
Set a max range of how many seeks we can expect when using keys
This was (s->read_time*5), but this was too low with small rows
This is can't be to high as otherwise we are likely to use
table scan.
*/
s->worst_seeks= (double) s->found_records / 5;
s->worst_seeks= min((double) s->found_records / 10,
(double) s->read_time*3);
if (s->worst_seeks < 2.0) // Fix for small tables
s->worst_seeks=2.0;
/* if (s->type == JT_EQ_REF)
continue; */
if (s->const_keys)
{
ha_rows records;
@ -1884,6 +1884,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
best=best_time=records=DBL_MAX;
KEYUSE *best_key=0;
uint best_max_key_part=0;
my_bool found_constrain= 0;
if (s->keyuse)
{ /* Use key if possible */
@ -1964,6 +1965,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
}
else
{
found_constrain= 1;
/*
Check if we found full key
*/
@ -2000,16 +2002,18 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
records=2.0; // Can't be as good as a unique
}
}
/* Limit the number of matched rows */
tmp= records;
set_if_smaller(tmp, (double) thd->variables.max_seeks_for_key);
if (table->used_keys & ((key_map) 1 << key))
{
/* we can use only index tree */
uint keys_per_block= table->file->block_size/2/
(keyinfo->key_length+table->file->ref_length)+1;
tmp=(record_count*(records+keys_per_block-1)/
keys_per_block);
tmp=record_count*(tmp+keys_per_block-1)/keys_per_block;
}
else
tmp=record_count*min(records,s->worst_seeks);
tmp=record_count*min(tmp,s->worst_seeks);
}
}
else
@ -2039,7 +2043,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
{
/*
Assume that the first key part matches 1% of the file
and that the hole key matches 10 (dupplicates) or 1
and that the hole key matches 10 (duplicates) or 1
(unique) records.
Assume also that more key matches proportionally more
records
@ -2071,6 +2075,8 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
records=(ulong) tmp;
}
}
/* Limit the number of matched rows */
set_if_smaller(tmp, (double) thd->variables.max_seeks_for_key);
if (table->used_keys & ((key_map) 1 << key))
{
/* we can use only index tree */
@ -2113,20 +2119,31 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
s->table->used_keys && best_key) &&
!(s->table->force_index && best_key))
{ // Check full join
ha_rows rnd_records= s->found_records;
if (s->on_expr)
{
tmp=rows2double(s->found_records); // Can't use read cache
tmp=rows2double(rnd_records); // Can't use read cache
}
else
{
tmp=(double) s->read_time;
/* Calculate time to read through cache */
/* Calculate time to read previous rows through cache */
tmp*=(1.0+floor((double) cache_record_length(join,idx)*
record_count /
(double) thd->variables.join_buff_size));
}
/*
If there is a restriction on the table, assume that 25% of the
rows can be skipped on next part.
This is to force tables that this table depends on before this
table
*/
if (found_constrain)
rnd_records-= rnd_records/4;
if (best == DBL_MAX ||
(tmp + record_count/(double) TIME_FOR_COMPARE*s->found_records <
(tmp + record_count/(double) TIME_FOR_COMPARE*rnd_records <
best + record_count/(double) TIME_FOR_COMPARE*records))
{
/*
@ -2134,7 +2151,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
will ensure that this will be used
*/
best=tmp;
records= rows2double(s->found_records);
records= rows2double(rnd_records);
best_key=0;
}
}