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Semi-join optimizations code cleanup:

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- Break down POSITION/advance_sj_state() into four classes 
  representing potential semi-join strategies.

- Treat all strategies uniformly (before, DuplicateWeedout 
  was special as it was the catch-all strategy. Now, we're 
  still relying on it to be the catch-all, but are able to 
  function,e.g. with firstmatch=on,duplicate_weedout=off.

- Update test results (checked)
This commit is contained in:
Sergey Petrunya
2011-11-23 04:25:52 +04:00
parent 7f746fbe74
commit 694ce95557
6 changed files with 780 additions and 489 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
mysql-test/r/subselect_sj2.result
View File

@ -323,8 +323,8 @@ WHERE Language='English' AND Percentage > 10 AND
t2.Population > 100000);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 range Population,Country Population 4 NULL 1 Using index condition; Rowid-ordered scan; Start temporary
1 PRIMARY t2 eq_ref PRIMARY,Population PRIMARY 3 test.t1.Country 1 Using where
1 PRIMARY t3 eq_ref PRIMARY,Percentage PRIMARY 33 test.t1.Country,const 1 Using index condition; Using where; End temporary
1 PRIMARY t2 eq_ref PRIMARY,Population PRIMARY 3 test.t1.Country 1 Using where; End temporary
1 PRIMARY t3 eq_ref PRIMARY,Percentage PRIMARY 33 test.t1.Country,const 1 Using index condition; Using where
set optimizer_switch=@bug35674_save_optimizer_switch;
DROP TABLE t1,t2,t3;
CREATE TABLE t1 (

4
mysql-test/r/subselect_sj2_jcl6.result
View File

@ -332,8 +332,8 @@ WHERE Language='English' AND Percentage > 10 AND
t2.Population > 100000);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 range Population,Country Population 4 NULL 1 Using index condition; Rowid-ordered scan; Start temporary
1 PRIMARY t2 eq_ref PRIMARY,Population PRIMARY 3 test.t1.Country 1 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 PRIMARY t3 eq_ref PRIMARY,Percentage PRIMARY 33 test.t1.Country,const 1 Using index condition; Using where; End temporary; Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan
1 PRIMARY t2 eq_ref PRIMARY,Population PRIMARY 3 test.t1.Country 1 Using where; End temporary; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 PRIMARY t3 eq_ref PRIMARY,Percentage PRIMARY 33 test.t1.Country,const 1 Using index condition; Using where; Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan
set optimizer_switch=@bug35674_save_optimizer_switch;
DROP TABLE t1,t2,t3;
CREATE TABLE t1 (

762
sql/opt_subselect.cc
View File

@ -2168,70 +2168,414 @@ bool find_eq_ref_candidate(TABLE *table, table_map sj_inner_tables)
See setup_semijoin_dups_elimination() for a description of what kinds of
join prefixes each strategy can handle.
*/
bool is_multiple_semi_joins(POSITION *prefix, uint idx, table_map inner_tables)
{
for (int i= (int)idx; i >= 0; i--)
{
TABLE_LIST *emb_sj_nest;
if ((emb_sj_nest= prefix[i].table->emb_sj_nest))
{
if (inner_tables & emb_sj_nest->sj_inner_tables)
return !test(inner_tables == emb_sj_nest->sj_inner_tables);
}
}
return FALSE;
}
void advance_sj_state(JOIN *join, table_map remaining_tables,
const JOIN_TAB *new_join_tab, uint idx,
void advance_sj_state(JOIN *join, table_map remaining_tables, uint idx,
double *current_record_count, double *current_read_time,
POSITION *loose_scan_pos)
{
TABLE_LIST *emb_sj_nest;
POSITION *pos= join->positions + idx;
remaining_tables &= ~new_join_tab->table->map;
bool disable_jbuf= join->thd->variables.join_cache_level == 0;
const JOIN_TAB *new_join_tab= pos->table;
Semi_join_strategy_picker *pickers[]=
{
&pos->firstmatch_picker,
&pos->loosescan_picker,
&pos->sjmat_picker,
&pos->dups_weedout_picker,
NULL,
};
pos->prefix_cost.convert_from_cost(*current_read_time);
pos->prefix_record_count= *current_record_count;
pos->sj_strategy= SJ_OPT_NONE;
pos->prefix_dups_producing_tables= join->cur_dups_producing_tables;
/* We're performing optimization inside SJ-Materialization nest */
if (join->emb_sjm_nest)
{
pos->invalidate_firstmatch_prefix();
pos->first_loosescan_table= MAX_TABLES;
pos->dupsweedout_tables= 0;
pos->sjm_scan_need_tables= 0;
/*
We're performing optimization inside SJ-Materialization nest:
- there are no other semi-joins inside semi-join nests
- attempts to build semi-join strategies here will confuse
the optimizer, so bail out.
*/
return;
}
/* Initialize the state or copy it from prev. tables */
/*
Update join->cur_sj_inner_tables (Used by FirstMatch in this function and
LooseScan detector in best_access_path)
*/
remaining_tables &= ~new_join_tab->table->map;
pos->prefix_dups_producing_tables= join->cur_dups_producing_tables;
TABLE_LIST *emb_sj_nest;
if ((emb_sj_nest= new_join_tab->emb_sj_nest))
{
/// join->cur_sj_inner_tables |= emb_sj_nest->sj_inner_tables;
join->cur_dups_producing_tables |= emb_sj_nest->sj_inner_tables;
/* Remove the sj_nest if all of its SJ-inner tables are in cur_table_map */
/// if (!(remaining_tables &
/// emb_sj_nest->sj_inner_tables & ~new_join_tab->table->map))
/// join->cur_sj_inner_tables &= ~emb_sj_nest->sj_inner_tables;
}
Semi_join_strategy_picker **strategy;
if (idx == join->const_tables)
{
pos->invalidate_firstmatch_prefix();
pos->first_loosescan_table= MAX_TABLES;
pos->dupsweedout_tables= 0;
pos->sjm_scan_need_tables= 0;
LINT_INIT(pos->sjm_scan_last_inner);
/* First table, initialize pickers */
for (strategy= pickers; *strategy != NULL; strategy++)
(*strategy)->set_empty();
pos->inner_tables_handled_with_other_sjs= 0;
}
else
{
// FirstMatch
pos->first_firstmatch_table=
(pos[-1].sj_strategy == SJ_OPT_FIRST_MATCH) ?
MAX_TABLES : pos[-1].first_firstmatch_table;
pos->first_firstmatch_rtbl= pos[-1].first_firstmatch_rtbl;
pos->firstmatch_need_tables= pos[-1].firstmatch_need_tables;
// LooseScan
pos->first_loosescan_table=
(pos[-1].sj_strategy == SJ_OPT_LOOSE_SCAN) ?
MAX_TABLES : pos[-1].first_loosescan_table;
pos->loosescan_need_tables= pos[-1].loosescan_need_tables;
// SJ-Materialization Scan
pos->sjm_scan_need_tables=
(pos[-1].sj_strategy == SJ_OPT_MATERIALIZE_SCAN) ?
0 : pos[-1].sjm_scan_need_tables;
pos->sjm_scan_last_inner= pos[-1].sjm_scan_last_inner;
// Duplicate Weedout
pos->dupsweedout_tables= pos[-1].dupsweedout_tables;
pos->first_dupsweedout_table= pos[-1].first_dupsweedout_table;
for (strategy= pickers; *strategy != NULL; strategy++)
{
(*strategy)->set_from_prev(pos - 1);
}
pos->inner_tables_handled_with_other_sjs=
pos[-1].inner_tables_handled_with_other_sjs;
}
table_map handled_by_fm_or_ls= 0;
/* FirstMatch Strategy */
pos->prefix_cost.convert_from_cost(*current_read_time);
pos->prefix_record_count= *current_record_count;
{
pos->sj_strategy= SJ_OPT_NONE;
for (strategy= pickers; *strategy != NULL; strategy++)
{
table_map handled_fanout;
sj_strategy_enum sj_strategy;
double rec_count= *current_record_count;
double read_time= *current_read_time;
if ((*strategy)->check_qep(join, idx, remaining_tables,
new_join_tab,
&rec_count,
&read_time,
&handled_fanout,
&sj_strategy,
loose_scan_pos))
{
/*
It's possible to use the strategy. Use it, if
- it removes semi-join fanout that was not removed before
- using it is cheaper than using something else,
and {if some other strategy has removed fanout
that this strategy is trying to remove, then it
did remove the fanout only for one semi-join}
This is to avoid a situation when
1. strategy X removes fanout for semijoin X,Y
2. using strategy Z is cheaper, but it only removes
fanout from semijoin X.
3. We have no clue what to do about fanount of semi-join Y.
*/
if ((join->cur_dups_producing_tables & handled_fanout) ||
(read_time < *current_read_time &&
!(handled_fanout & pos->inner_tables_handled_with_other_sjs)))
{
/* Mark strategy as used */
(*strategy)->mark_used();
pos->sj_strategy= sj_strategy;
*current_read_time= read_time;
*current_record_count= rec_count;
join->cur_dups_producing_tables &= ~handled_fanout;
//TODO: update bitmap of semi-joins that were handled together with
// others.
if (is_multiple_semi_joins(join->positions, idx, handled_fanout))
pos->inner_tables_handled_with_other_sjs |= handled_fanout;
}
else
{
/* We decided not to apply the strategy. */
(*strategy)->set_empty();
}
}
}
}
if ((emb_sj_nest= new_join_tab->emb_sj_nest))
{
join->cur_sj_inner_tables |= emb_sj_nest->sj_inner_tables;
/* Remove the sj_nest if all of its SJ-inner tables are in cur_table_map */
if (!(remaining_tables &
emb_sj_nest->sj_inner_tables & ~new_join_tab->table->map))
join->cur_sj_inner_tables &= ~emb_sj_nest->sj_inner_tables;
}
pos->prefix_cost.convert_from_cost(*current_read_time);
pos->prefix_record_count= *current_record_count;
}
void Sj_materialization_picker::set_from_prev(struct st_position *prev)
{
if (prev->sjmat_picker.is_used)
set_empty();
else
{
sjm_scan_need_tables= prev->sjmat_picker.sjm_scan_need_tables;
sjm_scan_last_inner= prev->sjmat_picker.sjm_scan_last_inner;
}
is_used= FALSE;
}
bool Sj_materialization_picker::check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
POSITION *loose_scan_pos)
{
bool sjm_scan;
SJ_MATERIALIZATION_INFO *mat_info;
if ((mat_info= at_sjmat_pos(join, remaining_tables,
new_join_tab, idx, &sjm_scan)))
{
if (sjm_scan)
{
/*
We can't yet evaluate this option yet. This is because we can't
accout for fanout of sj-inner tables yet:
ntX SJM-SCAN(it1 ... itN) | ot1 ... otN |
^(1) ^(2)
we're now at position (1). SJM temptable in general has multiple
records, so at point (1) we'll get the fanout from sj-inner tables (ie
there will be multiple record combinations).
The final join result will not contain any semi-join produced
fanout, i.e. tables within SJM-SCAN(...) will not contribute to
the cardinality of the join output. Extra fanout produced by
SJM-SCAN(...) will be 'absorbed' into fanout produced by ot1 ... otN.
The simple way to model this is to remove SJM-SCAN(...) fanout once
we reach the point #2.
*/
sjm_scan_need_tables=
new_join_tab->emb_sj_nest->sj_inner_tables |
new_join_tab->emb_sj_nest->nested_join->sj_depends_on |
new_join_tab->emb_sj_nest->nested_join->sj_corr_tables;
sjm_scan_last_inner= idx;
}
else
{
/* This is SJ-Materialization with lookups */
COST_VECT prefix_cost;
signed int first_tab= (int)idx - mat_info->tables;
double prefix_rec_count;
if (first_tab < (int)join->const_tables)
{
prefix_cost.zero();
prefix_rec_count= 1.0;
}
else
{
prefix_cost= join->positions[first_tab].prefix_cost;
prefix_rec_count= join->positions[first_tab].prefix_record_count;
}
double mat_read_time= prefix_cost.total_cost();
mat_read_time += mat_info->materialization_cost.total_cost() +
prefix_rec_count * mat_info->lookup_cost.total_cost();
/*
NOTE: When we pick to use SJM[-Scan] we don't memcpy its POSITION
elements to join->positions as that makes it hard to return things
back when making one step back in join optimization. That's done
after the QEP has been chosen.
*/
*read_time= mat_read_time;
*record_count= prefix_rec_count;
*handled_fanout= new_join_tab->emb_sj_nest->sj_inner_tables;
*strategy= SJ_OPT_MATERIALIZE;
return TRUE;
}
}
/* 4.A SJM-Scan second phase check */
if (sjm_scan_need_tables && /* Have SJM-Scan prefix */
!(sjm_scan_need_tables & remaining_tables))
{
TABLE_LIST *mat_nest=
join->positions[sjm_scan_last_inner].table->emb_sj_nest;
SJ_MATERIALIZATION_INFO *mat_info= mat_nest->sj_mat_info;
double prefix_cost;
double prefix_rec_count;
int first_tab= sjm_scan_last_inner + 1 - mat_info->tables;
/* Get the prefix cost */
if (first_tab == (int)join->const_tables)
{
prefix_rec_count= 1.0;
prefix_cost= 0.0;
}
else
{
prefix_cost= join->positions[first_tab - 1].prefix_cost.total_cost();
prefix_rec_count= join->positions[first_tab - 1].prefix_record_count;
}
/* Add materialization cost */
prefix_cost += mat_info->materialization_cost.total_cost() +
prefix_rec_count * mat_info->scan_cost.total_cost();
prefix_rec_count *= mat_info->rows;
uint i;
table_map rem_tables= remaining_tables;
for (i= idx; i != (first_tab + mat_info->tables - 1); i--)
rem_tables |= join->positions[i].table->table->map;
POSITION curpos, dummy;
/* Need to re-run best-access-path as we prefix_rec_count has changed */
bool disable_jbuf= (join->thd->variables.join_cache_level == 0);
for (i= first_tab + mat_info->tables; i <= idx; i++)
{
best_access_path(join, join->positions[i].table, rem_tables, i,
disable_jbuf, prefix_rec_count, &curpos, &dummy);
prefix_rec_count *= curpos.records_read;
prefix_cost += curpos.read_time;
}
*strategy= SJ_OPT_MATERIALIZE_SCAN;
*read_time= prefix_cost;
*record_count= prefix_rec_count;
*handled_fanout= mat_nest->sj_inner_tables;
return TRUE;
}
return FALSE;
}
void LooseScan_picker::set_from_prev(struct st_position *prev)
{
if (prev->loosescan_picker.is_used)
set_empty();
else
{
first_loosescan_table= prev->loosescan_picker.first_loosescan_table;
loosescan_need_tables= prev->loosescan_picker.loosescan_need_tables;
}
is_used= FALSE;
}
bool LooseScan_picker::check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
struct st_position *loose_scan_pos)
{
POSITION *first= join->positions + first_loosescan_table;
/*
LooseScan strategy can't handle interleaving between tables from the
semi-join that LooseScan is handling and any other tables.
If we were considering LooseScan for the join prefix (1)
and the table we're adding creates an interleaving (2)
then
stop considering loose scan
*/
if ((first_loosescan_table != MAX_TABLES) && // (1)
(first->table->emb_sj_nest->sj_inner_tables & remaining_tables) && //(2)
new_join_tab->emb_sj_nest != first->table->emb_sj_nest) //(2)
{
first_loosescan_table= MAX_TABLES;
}
/*
If we got an option to use LooseScan for the current table, start
considering using LooseScan strategy
*/
if (loose_scan_pos->read_time != DBL_MAX && !join->outer_join)
{
first_loosescan_table= idx;
loosescan_need_tables=
new_join_tab->emb_sj_nest->sj_inner_tables |
new_join_tab->emb_sj_nest->nested_join->sj_depends_on |
new_join_tab->emb_sj_nest->nested_join->sj_corr_tables;
}
if ((first_loosescan_table != MAX_TABLES) &&
!(remaining_tables & loosescan_need_tables) &&
(new_join_tab->table->map & loosescan_need_tables))
{
/*
Ok we have LooseScan plan and also have all LooseScan sj-nest's
inner tables and outer correlated tables into the prefix.
*/
first= join->positions + first_loosescan_table;
uint n_tables= my_count_bits(first->table->emb_sj_nest->sj_inner_tables);
/* Got a complete LooseScan range. Calculate its cost */
/*
The same problem as with FirstMatch - we need to save POSITIONs
somewhere but reserving space for all cases would require too
much space. We will re-calculate POSITION structures later on.
*/
bool disable_jbuf= (join->thd->variables.join_cache_level == 0);
optimize_wo_join_buffering(join, first_loosescan_table, idx,
remaining_tables,
TRUE, //first_alt
disable_jbuf ? join->table_count :
first_loosescan_table + n_tables,
record_count,
read_time);
/*
We don't yet have any other strategies that could handle this
semi-join nest (the other options are Duplicate Elimination or
Materialization, which need at least the same set of tables in
the join prefix to be considered) so unconditionally pick the
LooseScan.
*/
*strategy= SJ_OPT_LOOSE_SCAN;
*handled_fanout= first->table->emb_sj_nest->sj_inner_tables;
return TRUE;
}
return FALSE;
}
void Firstmatch_picker::set_from_prev(struct st_position *prev)
{
if (prev->firstmatch_picker.is_used)
invalidate_firstmatch_prefix();
else
{
first_firstmatch_table= prev->firstmatch_picker.first_firstmatch_table;
first_firstmatch_rtbl= prev->firstmatch_picker.first_firstmatch_rtbl;
firstmatch_need_tables= prev->firstmatch_picker.firstmatch_need_tables;
}
is_used= FALSE;
}
bool Firstmatch_picker::check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
POSITION *loose_scan_pos)
{
if (new_join_tab->emb_sj_nest &&
optimizer_flag(join->thd, OPTIMIZER_SWITCH_FIRSTMATCH) &&
!join->outer_join)
@ -2259,298 +2603,102 @@ void advance_sj_state(JOIN *join, table_map remaining_tables,
((remaining_tables | new_join_tab->table->map) & sj_inner_tables)))
{
/* Start tracking potential FirstMatch range */
pos->first_firstmatch_table= idx;
pos->firstmatch_need_tables= sj_inner_tables;
pos->first_firstmatch_rtbl= remaining_tables;
first_firstmatch_table= idx;
firstmatch_need_tables= sj_inner_tables;
first_firstmatch_rtbl= remaining_tables;
}
if (pos->in_firstmatch_prefix())
if (in_firstmatch_prefix())
{
if (outer_corr_tables & pos->first_firstmatch_rtbl)
if (outer_corr_tables & first_firstmatch_rtbl)
{
/*
Trying to add an sj-inner table whose sj-nest has an outer correlated
table that was not in the prefix. This means FirstMatch can't be used.
*/
pos->invalidate_firstmatch_prefix();
invalidate_firstmatch_prefix();
}
else
{
/* Record that we need all of this semi-join's inner tables, too */
pos->firstmatch_need_tables|= sj_inner_tables;
firstmatch_need_tables|= sj_inner_tables;
}
if (pos->in_firstmatch_prefix() &&
!(pos->firstmatch_need_tables & remaining_tables))
if (in_firstmatch_prefix() &&
!(firstmatch_need_tables & remaining_tables))
{
/*
Got a complete FirstMatch range.
Calculate correct costs and fanout
*/
optimize_wo_join_buffering(join, pos->first_firstmatch_table, idx,
optimize_wo_join_buffering(join, first_firstmatch_table, idx,
remaining_tables, FALSE, idx,
current_record_count,
current_read_time);
record_count,
read_time);
/*
We don't yet know what are the other strategies, so pick the
FirstMatch.
We ought to save the alternate POSITIONs produced by
optimize_wo_join_buffering but the problem is that providing save
space uses too much space. Instead, we will re-calculate the
alternate POSITIONs after we've picked the best QEP.
*/
pos->sj_strategy= SJ_OPT_FIRST_MATCH;
handled_by_fm_or_ls= pos->firstmatch_need_tables;
*handled_fanout= firstmatch_need_tables;
/* *record_count and *read_time were set by the above call */
*strategy= SJ_OPT_FIRST_MATCH;
return TRUE;
}
}
}
return FALSE;
}
/* LooseScan Strategy */
{
POSITION *first=join->positions+pos->first_loosescan_table;
/*
LooseScan strategy can't handle interleaving between tables from the
semi-join that LooseScan is handling and any other tables.
If we were considering LooseScan for the join prefix (1)
and the table we're adding creates an interleaving (2)
then
stop considering loose scan
*/
if ((pos->first_loosescan_table != MAX_TABLES) && // (1)
(first->table->emb_sj_nest->sj_inner_tables & remaining_tables) && //(2)
new_join_tab->emb_sj_nest != first->table->emb_sj_nest) //(2)
{
pos->first_loosescan_table= MAX_TABLES;
}
/*
If we got an option to use LooseScan for the current table, start
considering using LooseScan strategy
*/
if (loose_scan_pos->read_time != DBL_MAX && !join->outer_join)
{
pos->first_loosescan_table= idx;
pos->loosescan_need_tables=
new_join_tab->emb_sj_nest->sj_inner_tables |
new_join_tab->emb_sj_nest->nested_join->sj_depends_on |
new_join_tab->emb_sj_nest->nested_join->sj_corr_tables;
}
if ((pos->first_loosescan_table != MAX_TABLES) &&
!(remaining_tables & pos->loosescan_need_tables) &&
(pos->table->table->map & pos->loosescan_need_tables))
{
/*
Ok we have LooseScan plan and also have all LooseScan sj-nest's
inner tables and outer correlated tables into the prefix.
*/
first=join->positions + pos->first_loosescan_table;
uint n_tables= my_count_bits(first->table->emb_sj_nest->sj_inner_tables);
/* Got a complete LooseScan range. Calculate its cost */
/*
The same problem as with FirstMatch - we need to save POSITIONs
somewhere but reserving space for all cases would require too
much space. We will re-calculate POSITION structures later on.
*/
optimize_wo_join_buffering(join, pos->first_loosescan_table, idx,
remaining_tables,
TRUE, //first_alt
disable_jbuf ? join->table_count :
pos->first_loosescan_table + n_tables,
current_record_count,
current_read_time);
/*
We don't yet have any other strategies that could handle this
semi-join nest (the other options are Duplicate Elimination or
Materialization, which need at least the same set of tables in
the join prefix to be considered) so unconditionally pick the
LooseScan.
*/
pos->sj_strategy= SJ_OPT_LOOSE_SCAN;
handled_by_fm_or_ls= first->table->emb_sj_nest->sj_inner_tables;
}
}
/*
Update join->cur_sj_inner_tables (Used by FirstMatch in this function and
LooseScan detector in best_access_path)
*/
if ((emb_sj_nest= new_join_tab->emb_sj_nest))
{
join->cur_sj_inner_tables |= emb_sj_nest->sj_inner_tables;
join->cur_dups_producing_tables |= emb_sj_nest->sj_inner_tables;
/* Remove the sj_nest if all of its SJ-inner tables are in cur_table_map */
if (!(remaining_tables &
emb_sj_nest->sj_inner_tables & ~new_join_tab->table->map))
join->cur_sj_inner_tables &= ~emb_sj_nest->sj_inner_tables;
}
join->cur_dups_producing_tables &= ~handled_by_fm_or_ls;
/* 4. SJ-Materialization and SJ-Materialization-scan strategy handler */
bool sjm_scan;
SJ_MATERIALIZATION_INFO *mat_info;
if ((mat_info= at_sjmat_pos(join, remaining_tables,
new_join_tab, idx, &sjm_scan)))
{
if (sjm_scan)
{
/*
We can't yet evaluate this option yet. This is because we can't
accout for fanout of sj-inner tables yet:
ntX SJM-SCAN(it1 ... itN) | ot1 ... otN |
^(1) ^(2)
we're now at position (1). SJM temptable in general has multiple
records, so at point (1) we'll get the fanout from sj-inner tables (ie
there will be multiple record combinations).
The final join result will not contain any semi-join produced
fanout, i.e. tables within SJM-SCAN(...) will not contribute to
the cardinality of the join output. Extra fanout produced by
SJM-SCAN(...) will be 'absorbed' into fanout produced by ot1 ... otN.
The simple way to model this is to remove SJM-SCAN(...) fanout once
we reach the point #2.
*/
pos->sjm_scan_need_tables=
new_join_tab->emb_sj_nest->sj_inner_tables |
new_join_tab->emb_sj_nest->nested_join->sj_depends_on |
new_join_tab->emb_sj_nest->nested_join->sj_corr_tables;
pos->sjm_scan_last_inner= idx;
}
void Duplicate_weedout_picker::set_from_prev(POSITION *prev)
{
if (prev->dups_weedout_picker.is_used)
set_empty();
else
{
/* This is SJ-Materialization with lookups */
COST_VECT prefix_cost;
signed int first_tab= (int)idx - mat_info->tables;
double prefix_rec_count;
if (first_tab < (int)join->const_tables)
{
prefix_cost.zero();
prefix_rec_count= 1.0;
}
else
{
prefix_cost= join->positions[first_tab].prefix_cost;
prefix_rec_count= join->positions[first_tab].prefix_record_count;
dupsweedout_tables= prev->dups_weedout_picker.dupsweedout_tables;
first_dupsweedout_table= prev->dups_weedout_picker.first_dupsweedout_table;
}
is_used= FALSE;
}
double mat_read_time= prefix_cost.total_cost();
mat_read_time += mat_info->materialization_cost.total_cost() +
prefix_rec_count * mat_info->lookup_cost.total_cost();
if (mat_read_time < *current_read_time || join->cur_dups_producing_tables)
{
/*
NOTE: When we pick to use SJM[-Scan] we don't memcpy its POSITION
elements to join->positions as that makes it hard to return things
back when making one step back in join optimization. That's done
after the QEP has been chosen.
*/
pos->sj_strategy= SJ_OPT_MATERIALIZE;
*current_read_time= mat_read_time;
*current_record_count= prefix_rec_count;
join->cur_dups_producing_tables&=
~new_join_tab->emb_sj_nest->sj_inner_tables;
}
}
}
/* 4.A SJM-Scan second phase check */
if (pos->sjm_scan_need_tables && /* Have SJM-Scan prefix */
!(pos->sjm_scan_need_tables & remaining_tables))
{
TABLE_LIST *mat_nest=
join->positions[pos->sjm_scan_last_inner].table->emb_sj_nest;
SJ_MATERIALIZATION_INFO *mat_info= mat_nest->sj_mat_info;
double prefix_cost;
double prefix_rec_count;
int first_tab= pos->sjm_scan_last_inner + 1 - mat_info->tables;
/* Get the prefix cost */
if (first_tab == (int)join->const_tables)
{
prefix_rec_count= 1.0;
prefix_cost= 0.0;
}
else
{
prefix_cost= join->positions[first_tab - 1].prefix_cost.total_cost();
prefix_rec_count= join->positions[first_tab - 1].prefix_record_count;
}
/* Add materialization cost */
prefix_cost += mat_info->materialization_cost.total_cost() +
prefix_rec_count * mat_info->scan_cost.total_cost();
prefix_rec_count *= mat_info->rows;
uint i;
table_map rem_tables= remaining_tables;
for (i= idx; i != (first_tab + mat_info->tables - 1); i--)
rem_tables |= join->positions[i].table->table->map;
POSITION curpos, dummy;
/* Need to re-run best-access-path as we prefix_rec_count has changed */
for (i= first_tab + mat_info->tables; i <= idx; i++)
{
best_access_path(join, join->positions[i].table, rem_tables, i,
disable_jbuf, prefix_rec_count, &curpos, &dummy);
prefix_rec_count *= curpos.records_read;
prefix_cost += curpos.read_time;
}
/*
Use the strategy if
* it is cheaper then what we've had, or
* we haven't picked any other semi-join strategy yet
In the second case, we pick this strategy unconditionally because
comparing cost without semi-join duplicate removal with cost with
duplicate removal is not an apples-to-apples comparison.
*/
if (prefix_cost < *current_read_time || join->cur_dups_producing_tables)
{
pos->sj_strategy= SJ_OPT_MATERIALIZE_SCAN;
*current_read_time= prefix_cost;
*current_record_count= prefix_rec_count;
join->cur_dups_producing_tables&= ~mat_nest->sj_inner_tables;
}
}
/* 5. Duplicate Weedout strategy handler */
{
/*
Duplicate weedout can be applied after all ON-correlated and
correlated
*/
bool Duplicate_weedout_picker::check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
POSITION *loose_scan_pos
)
{
TABLE_LIST *nest;
if ((nest= new_join_tab->emb_sj_nest))
{
if (!pos->dupsweedout_tables)
pos->first_dupsweedout_table= idx;
if (!dupsweedout_tables)
first_dupsweedout_table= idx;
pos->dupsweedout_tables |= nest->sj_inner_tables |
dupsweedout_tables |= nest->sj_inner_tables |
nest->nested_join->sj_depends_on |
nest->nested_join->sj_corr_tables;
}
if (pos->dupsweedout_tables)
if (dupsweedout_tables)
{
/* we're in the process of constructing a DuplicateWeedout range */
TABLE_LIST *emb= new_join_tab->table->pos_in_table_list->embedding;
/* and we've entered an inner side of an outer join*/
if (emb && emb->on_expr)
pos->dupsweedout_tables |= emb->nested_join->used_tables;
dupsweedout_tables |= emb->nested_join->used_tables;
}
if (pos->dupsweedout_tables &&
!(remaining_tables &
~new_join_tab->table->map & pos->dupsweedout_tables))
/* If this is the last table that we need for DuplicateWeedout range */
if (dupsweedout_tables && !(remaining_tables & ~new_join_tab->table->map &
dupsweedout_tables))
{
/*
Ok, reached a state where we could put a dups weedout point.
@ -2566,7 +2714,7 @@ void advance_sj_state(JOIN *join, table_map remaining_tables,
We need to calculate the cost in case #2 also because we need to make
choice between this join order and others.
*/
uint first_tab= pos->first_dupsweedout_table;
uint first_tab= first_dupsweedout_table;
double dups_cost;
double prefix_rec_count;
double sj_inner_fanout= 1.0;
@ -2586,7 +2734,7 @@ void advance_sj_state(JOIN *join, table_map remaining_tables,
}
table_map dups_removed_fanout= 0;
for (uint j= pos->first_dupsweedout_table; j <= idx; j++)
for (uint j= first_dupsweedout_table; j <= idx; j++)
{
POSITION *p= join->positions + j;
dups_cost += p->read_time;
@ -2623,23 +2771,13 @@ void advance_sj_state(JOIN *join, table_map remaining_tables,
one_lookup_cost;
dups_cost += write_cost + full_lookup_cost;
/*
Use the strategy if
* it is cheaper then what we've had, or
* we haven't picked any other semi-join strategy yet
The second part is necessary because this strategy is the last one
to consider (it needs "the most" tables in the prefix) and we can't
leave duplicate-producing tables not handled by any strategy.
*/
if (dups_cost < *current_read_time || join->cur_dups_producing_tables)
{
pos->sj_strategy= SJ_OPT_DUPS_WEEDOUT;
*current_read_time= dups_cost;
*current_record_count= prefix_rec_count * sj_outer_fanout;
join->cur_dups_producing_tables &= ~dups_removed_fanout;
}
}
*read_time= dups_cost;
*record_count= prefix_rec_count * sj_outer_fanout;
*handled_fanout= dups_removed_fanout;
*strategy= SJ_OPT_DUPS_WEEDOUT;
return TRUE;
}
return FALSE;
}
@ -2836,11 +2974,11 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
}
else if (pos->sj_strategy == SJ_OPT_MATERIALIZE_SCAN)
{
POSITION *first_inner= join->best_positions + pos->sjm_scan_last_inner;
POSITION *first_inner= join->best_positions + pos->sjmat_picker.sjm_scan_last_inner;
SJ_MATERIALIZATION_INFO *sjm= first_inner->table->emb_sj_nest->sj_mat_info;
sjm->is_used= TRUE;
sjm->is_sj_scan= TRUE;
first= pos->sjm_scan_last_inner - sjm->tables + 1;
first= pos->sjmat_picker.sjm_scan_last_inner - sjm->tables + 1;
memcpy(join->best_positions + first,
sjm->positions, sizeof(POSITION) * sjm->tables);
join->best_positions[first].sj_strategy= SJ_OPT_MATERIALIZE_SCAN;
@ -2878,7 +3016,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
if (pos->sj_strategy == SJ_OPT_FIRST_MATCH)
{
first= pos->first_firstmatch_table;
first= pos->firstmatch_picker.first_firstmatch_table;
join->best_positions[first].sj_strategy= SJ_OPT_FIRST_MATCH;
join->best_positions[first].n_sj_tables= tablenr - first + 1;
POSITION dummy; // For loose scan paths
@ -2911,7 +3049,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
if (pos->sj_strategy == SJ_OPT_LOOSE_SCAN)
{
first= pos->first_loosescan_table;
first= pos->loosescan_picker.first_loosescan_table;
POSITION *first_pos= join->best_positions + first;
POSITION loose_scan_pos; // For loose scan paths
double record_count= (first== join->const_tables)? 1.0:
@ -2950,7 +3088,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
Duplicate Weedout starting at pos->first_dupsweedout_table, ending at
this table.
*/
first= pos->first_dupsweedout_table;
first= pos->dups_weedout_picker.first_dupsweedout_table;
join->best_positions[first].sj_strategy= SJ_OPT_DUPS_WEEDOUT;
join->best_positions[first].n_sj_tables= tablenr - first + 1;
}
@ -3893,8 +4031,8 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
/* Calculate key length */
keylen= 0;
keyno= pos->loosescan_key;
for (uint kp=0; kp < pos->loosescan_parts; kp++)
keyno= pos->loosescan_picker.loosescan_key;
for (uint kp=0; kp < pos->loosescan_picker.loosescan_parts; kp++)
keylen += tab->table->key_info[keyno].key_part[kp].store_length;
tab->loosescan_key_len= keylen;

7
sql/opt_subselect.h
View File

@ -263,8 +263,8 @@ public:
{
pos->records_read= best_loose_scan_records;
pos->key= best_loose_scan_start_key;
pos->loosescan_key= best_loose_scan_key;
pos->loosescan_parts= best_max_loose_keypart + 1;
pos->loosescan_picker.loosescan_key= best_loose_scan_key;
pos->loosescan_picker.loosescan_parts= best_max_loose_keypart + 1;
pos->use_join_buffer= FALSE;
pos->table= tab;
// todo need ref_depend_map ?
@ -277,8 +277,7 @@ public:
};
void advance_sj_state(JOIN *join, const table_map remaining_tables,
const JOIN_TAB *new_join_tab, uint idx,
void advance_sj_state(JOIN *join, const table_map remaining_tables, uint idx,
double *current_record_count, double *current_read_time,
POSITION *loose_scan_pos);
void restore_prev_sj_state(const table_map remaining_tables,

23
sql/sql_select.cc
View File

@ -85,7 +85,7 @@ static int join_tab_cmp_embedded_first(const void *emb, const void* ptr1, const
static bool find_best(JOIN *join,table_map rest_tables,uint index,
double record_count,double read_time);
static uint cache_record_length(JOIN *join,uint index);
static bool get_best_combination(JOIN *join);
bool get_best_combination(JOIN *join);
static store_key *get_store_key(THD *thd,
KEYUSE *keyuse, table_map used_tables,
KEY_PART_INFO *key_part, uchar *key_buff,
@ -4883,7 +4883,7 @@ void set_position(JOIN *join,uint idx,JOIN_TAB *table,KEYUSE *key)
join->positions[idx].records_read=1.0; /* This is a const table */
join->positions[idx].ref_depend_map= 0;
join->positions[idx].loosescan_key= MAX_KEY; /* Not a LooseScan */
// join->positions[idx].loosescan_key= MAX_KEY; /* Not a LooseScan */
join->positions[idx].sj_strategy= SJ_OPT_NONE;
join->positions[idx].use_join_buffer= FALSE;
@ -5533,7 +5533,7 @@ best_access_path(JOIN *join,
pos->key= best_key;
pos->table= s;
pos->ref_depend_map= best_ref_depends_map;
pos->loosescan_key= MAX_KEY;
pos->loosescan_picker.loosescan_key= MAX_KEY;
pos->use_join_buffer= best_uses_jbuf;
loose_scan_opt.save_to_position(s, loose_scan_pos);
@ -5840,7 +5840,7 @@ optimize_straight_join(JOIN *join, table_map join_tables)
/* compute the cost of the new plan extended with 's' */
record_count*= join->positions[idx].records_read;
read_time+= join->positions[idx].read_time;
advance_sj_state(join, join_tables, s, idx, &record_count, &read_time,
advance_sj_state(join, join_tables, idx, &record_count, &read_time,
&loose_scan_pos);
join_tables&= ~(s->table->map);
@ -6356,7 +6356,7 @@ best_extension_by_limited_search(JOIN *join,
current_record_count= record_count * position->records_read;
current_read_time= read_time + position->read_time;
advance_sj_state(join, remaining_tables, s, idx, &current_record_count,
advance_sj_state(join, remaining_tables, idx, &current_record_count,
&current_read_time, &loose_scan_pos);
/* Expand only partial plans with lower cost than the best QEP so far */
@ -6513,7 +6513,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
*/
double current_record_count=record_count*records;
double current_read_time=read_time+best;
advance_sj_state(join, rest_tables, s, idx, &current_record_count,
advance_sj_state(join, rest_tables, idx, &current_record_count,
&current_read_time, &loose_scan_pos);
if (best_record_count > current_record_count ||
@ -7013,7 +7013,7 @@ static Item * const null_ptr= NULL;
TRUE Out of memory
*/
static bool
bool
get_best_combination(JOIN *join)
{
uint tablenr;
@ -7091,13 +7091,6 @@ get_best_combination(JOIN *join)
*j= *join->best_positions[tablenr].table;
#if 0
/* SJ-Materialization is represented with join tab ranges */
if (j->sj_strategy == SJ_OPT_MATERIALIZE ||
j->sj_strategy == SJ_OPT_MATERIALIZE)
j->sj_strategy= SJ_OPT_NONE;
#endif
j->bush_root_tab= sjm_nest_root;
form=join->table[tablenr]=j->table;
@ -7120,7 +7113,7 @@ get_best_combination(JOIN *join)
(join->best_positions[tablenr].sj_strategy == SJ_OPT_LOOSE_SCAN))
{
j->type=JT_ALL;
j->index= join->best_positions[tablenr].loosescan_key;
j->index= join->best_positions[tablenr].loosescan_picker.loosescan_key;
if (tablenr != join->const_tables)
join->full_join=1;
}

339
sql/sql_select.h
View File

@ -158,6 +158,17 @@ enum enum_nested_loop_state
};
/* Possible sj_strategy values */
enum sj_strategy_enum
{
SJ_OPT_NONE=0,
SJ_OPT_DUPS_WEEDOUT=1,
SJ_OPT_LOOSE_SCAN =2,
SJ_OPT_FIRST_MATCH =3,
SJ_OPT_MATERIALIZE =4,
SJ_OPT_MATERIALIZE_SCAN=5
};
/* Values for JOIN_TAB::packed_info */
#define TAB_INFO_HAVE_VALUE 1
#define TAB_INFO_USING_INDEX 2
@ -374,7 +385,7 @@ typedef struct st_join_table {
POSITION::sj_strategy field. This field is set up by the
fix_semijoin_strategies_for_picked_join_order.
*/
uint sj_strategy;
enum sj_strategy_enum sj_strategy;
uint n_sj_tables;
@ -496,66 +507,126 @@ enum_nested_loop_state
end_write_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
bool end_of_records);
/* psergey */
/**
Information about a position of table within a join order. Used in join
optimization.
struct st_position;
class Semi_join_strategy_picker
{
public:
/* Called when starting to build a new join prefix */
virtual void set_empty() = 0;
/*
Update internal state after another table has been added to the join
prefix
*/
virtual void set_from_prev(struct st_position *prev) = 0;
virtual bool check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
struct st_position *loose_scan_pos) = 0;
virtual void mark_used() = 0;
virtual ~Semi_join_strategy_picker() {}
};
/*
Duplicate Weedout strategy optimization state
*/
typedef struct st_position
class Duplicate_weedout_picker : public Semi_join_strategy_picker
{
/* The first table that the strategy will need to handle */
uint first_dupsweedout_table;
/*
Tables that we will need to have in the prefix to do the weedout step
(all inner and all outer that the involved semi-joins are correlated with)
*/
table_map dupsweedout_tables;
bool is_used;
public:
void set_empty()
{
dupsweedout_tables= 0;
first_dupsweedout_table= MAX_TABLES;
is_used= FALSE;
}
void set_from_prev(struct st_position *prev);
bool check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *stratey,
struct st_position *loose_scan_pos);
void mark_used() { is_used= TRUE; }
friend void fix_semijoin_strategies_for_picked_join_order(JOIN *join);
};
class Firstmatch_picker : public Semi_join_strategy_picker
{
/*
The "fanout": number of output rows that will be produced (after
pushed down selection condition is applied) per each row combination of
previous tables.
Index of the first inner table that we intend to handle with this
strategy
*/
double records_read;
uint first_firstmatch_table;
/*
Cost accessing the table in course of the entire complete join execution,
i.e. cost of one access method use (e.g. 'range' or 'ref' scan ) times
number the access method will be invoked.
Tables that were not in the join prefix when we've started considering
FirstMatch strategy.
*/
double read_time;
JOIN_TAB *table;
table_map first_firstmatch_rtbl;
/*
NULL - 'index' or 'range' or 'index_merge' or 'ALL' access is used.
Other - [eq_]ref[_or_null] access is used. Pointer to {t.keypart1 = expr}
Tables that need to be in the prefix before we can calculate the cost
of using FirstMatch strategy.
*/
KEYUSE *key;
table_map firstmatch_need_tables;
/* If ref-based access is used: bitmap of tables this table depends on */
table_map ref_depend_map;
bool is_used;
bool use_join_buffer;
bool in_firstmatch_prefix() { return (first_firstmatch_table != MAX_TABLES); }
void invalidate_firstmatch_prefix() { first_firstmatch_table= MAX_TABLES; }
public:
void set_empty()
{
invalidate_firstmatch_prefix();
is_used= FALSE;
}
void set_from_prev(struct st_position *prev);
bool check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
struct st_position *loose_scan_pos);
void mark_used() { is_used= TRUE; }
friend void fix_semijoin_strategies_for_picked_join_order(JOIN *join);
};
/* These form a stack of partial join order costs and output sizes */
COST_VECT prefix_cost;
double prefix_record_count;
/*
Current optimization state: Semi-join strategy to be used for this
and preceding join tables.
Join optimizer sets this for the *last* join_tab in the
duplicate-generating range. That is, in order to interpret this field,
one needs to traverse join->[best_]positions array from right to left.
When you see a join table with sj_strategy!= SJ_OPT_NONE, some other
field (depending on the strategy) tells how many preceding positions
this applies to. The values of covered_preceding_positions->sj_strategy
must be ignored.
*/
uint sj_strategy;
/*
Valid only after fix_semijoin_strategies_for_picked_join_order() call:
if sj_strategy!=SJ_OPT_NONE, this is the number of subsequent tables that
are covered by the specified semi-join strategy
*/
uint n_sj_tables;
/* LooseScan strategy members */
class LooseScan_picker : public Semi_join_strategy_picker
{
/* The first (i.e. driving) table we're doing loose scan for */
uint first_loosescan_table;
/*
@ -573,36 +644,46 @@ typedef struct st_position
uint loosescan_key; // final (one for strategy instance )
uint loosescan_parts; /* Number of keyparts to be kept distinct */
/* FirstMatch strategy */
/*
Index of the first inner table that we intend to handle with this
strategy
*/
uint first_firstmatch_table;
/*
Tables that were not in the join prefix when we've started considering
FirstMatch strategy.
*/
table_map first_firstmatch_rtbl;
/*
Tables that need to be in the prefix before we can calculate the cost
of using FirstMatch strategy.
*/
table_map firstmatch_need_tables;
bool is_used;
public:
void set_empty()
{
first_loosescan_table= MAX_TABLES;
is_used= FALSE;
}
bool in_firstmatch_prefix() { return (first_firstmatch_table != MAX_TABLES); }
void invalidate_firstmatch_prefix() { first_firstmatch_table= MAX_TABLES; }
void set_from_prev(struct st_position *prev);
bool check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
struct st_position *loose_scan_pos);
void mark_used() { is_used= TRUE; }
/* Duplicate Weedout strategy */
/* The first table that the strategy will need to handle */
uint first_dupsweedout_table;
/*
Tables that we will need to have in the prefix to do the weedout step
(all inner and all outer that the involved semi-joins are correlated with)
*/
table_map dupsweedout_tables;
friend class Loose_scan_opt;
friend void best_access_path(JOIN *join,
JOIN_TAB *s,
table_map remaining_tables,
uint idx,
bool disable_jbuf,
double record_count,
struct st_position *pos,
struct st_position *loose_scan_pos);
friend bool get_best_combination(JOIN *join);
friend int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
uint no_jbuf_after);
friend void fix_semijoin_strategies_for_picked_join_order(JOIN *join);
};
class Sj_materialization_picker : public Semi_join_strategy_picker
{
bool is_used;
/* SJ-Materialization-Scan strategy */
/* The last inner table (valid once we're after it) */
uint sjm_scan_last_inner;
/*
@ -612,9 +693,101 @@ typedef struct st_position
*/
table_map sjm_scan_need_tables;
table_map prefix_dups_producing_tables;
} POSITION;
public:
void set_empty()
{
sjm_scan_need_tables= 0;
LINT_INIT(sjm_scan_last_inner);
is_used= FALSE;
}
void set_from_prev(struct st_position *prev);
bool check_qep(JOIN *join,
uint idx,
table_map remaining_tables,
const JOIN_TAB *new_join_tab,
double *record_count,
double *read_time,
table_map *handled_fanout,
sj_strategy_enum *strategy,
struct st_position *loose_scan_pos);
void mark_used() { is_used= TRUE; }
friend void fix_semijoin_strategies_for_picked_join_order(JOIN *join);
};
/**
Information about a position of table within a join order. Used in join
optimization.
*/
typedef struct st_position
{
/* The table that's put into join order */
JOIN_TAB *table;
/*
The "fanout": number of output rows that will be produced (after
pushed down selection condition is applied) per each row combination of
previous tables.
*/
double records_read;
/*
Cost accessing the table in course of the entire complete join execution,
i.e. cost of one access method use (e.g. 'range' or 'ref' scan ) times
number the access method will be invoked.
*/
double read_time;
/* Cumulative cost and record count for the join prefix */
COST_VECT prefix_cost;
double prefix_record_count;
/*
NULL - 'index' or 'range' or 'index_merge' or 'ALL' access is used.
Other - [eq_]ref[_or_null] access is used. Pointer to {t.keypart1 = expr}
*/
KEYUSE *key;
/* If ref-based access is used: bitmap of tables this table depends on */
table_map ref_depend_map;
/*
TRUE <=> join buffering will be used. At the moment this is based on
*very* imprecise guesses made in best_access_path().
*/
bool use_join_buffer;
/*
Current optimization state: Semi-join strategy to be used for this
and preceding join tables.
Join optimizer sets this for the *last* join_tab in the
duplicate-generating range. That is, in order to interpret this field,
one needs to traverse join->[best_]positions array from right to left.
When you see a join table with sj_strategy!= SJ_OPT_NONE, some other
field (depending on the strategy) tells how many preceding positions
this applies to. The values of covered_preceding_positions->sj_strategy
must be ignored.
*/
enum sj_strategy_enum sj_strategy;
/*
Valid only after fix_semijoin_strategies_for_picked_join_order() call:
if sj_strategy!=SJ_OPT_NONE, this is the number of subsequent tables that
are covered by the specified semi-join strategy
*/
uint n_sj_tables;
table_map prefix_dups_producing_tables;
table_map inner_tables_handled_with_other_sjs;
Duplicate_weedout_picker dups_weedout_picker;
Firstmatch_picker firstmatch_picker;
LooseScan_picker loosescan_picker;
Sj_materialization_picker sjmat_picker;
} POSITION;
typedef struct st_rollup
{
@ -626,18 +799,6 @@ typedef struct st_rollup
} ROLLUP;
#define SJ_OPT_NONE 0
#define SJ_OPT_DUPS_WEEDOUT 1
#define SJ_OPT_LOOSE_SCAN 2
#define SJ_OPT_FIRST_MATCH 3
#define SJ_OPT_MATERIALIZE 4
#define SJ_OPT_MATERIALIZE_SCAN 5
inline bool sj_is_materialize_strategy(uint strategy)
{
return strategy >= SJ_OPT_MATERIALIZE;
}
class JOIN_TAB_RANGE: public Sql_alloc
{
public: