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MWL#68 Subquery optimization: Efficient NOT IN execution with NULLs

Browse source 
This patch implements correct NULL semantics for materialized subquery execution.
The implementation has the following properties and main limitations:
- It passes all query result tests, but fails a number of EXPLAIN tests because of
  changed plans.
- The EXPLAIN output for partial matching is not decided yet.
- It works only when all necessary indexes fit into main memory. Notice that these
  are not the general B-tree/Hash indexes, but instead much more compact ones,
  therefore this limitation may not be a problem in many practical cases.
- It doesn't contain specialized tests.
- In several places the implementation uses methods that are modified copies of
  other similar methods. These cases need to be refactored to avoid code duplication.
- Add a test if the predicate is top-level just before deciding on partial matching.
  If it is top-level, use a more efficient exec method (index lookup).
- Add sorting of indexes according to their selectivity. The code is almost there.
- Needs more comments, and to sync existing ones with the implementation.

sql/item_cmpfunc.h:
  Expose the Arg_comparator of a comparison predicate. This makes it possible to
  directly get the comparison result {-1,0,1}, which is not possible through the
  val_XXX() methods which "fold" such results into a boolean.
sql/item_subselect.cc:
  The core of the implementation of MWL#68.
sql/item_subselect.h:
  The core of the implementation of MWL#68.
sql/opt_subselect.cc:
  Removed the limitation for materialized subquery execution that it is applicable only
  for top-level predicates.
sql/sql_class.cc:
  New class select_materialize_with_stats that collects data statistics about
  the data being inserted into the target table.
sql/sql_class.h:
  New class select_materialize_with_stats that collects data statistics about
  the data being inserted into the target table.
sql/sql_select.cc:
  - more complete initialization of the TABLE object of a temp table.
  - call setup_subquery_materialization at one more exit point.
This commit is contained in:
unknown 2010-02-19 23:55:57 +02:00
parent d63959eed3
commit 5515bcba06
7 changed files with 1894 additions and 206 deletions
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1
sql/item_cmpfunc.h
View file

@ -350,6 +350,7 @@ public:
CHARSET_INFO *compare_collation() { return cmp.cmp_collation.collation; }
uint decimal_precision() const { return 1; }
void top_level_item() { abort_on_null= TRUE; }
Arg_comparator *get_comparator() { return &cmp; }
friend class Arg_comparator;
};

1538
sql/item_subselect.cc
View file

File diff suppressed because it is too large Load diff

398
sql/item_subselect.h
View file

@ -297,7 +297,7 @@ public:
Representation of IN subquery predicates of the form
"left_expr IN (SELECT ...)".
@detail
@details
This class has:
- A "subquery execution engine" (as a subclass of Item_subselect) that allows
it to evaluate subqueries. (and this class participates in execution by
@ -319,6 +319,12 @@ protected:
*/
List<Cached_item> *left_expr_cache;
bool first_execution;
/*
Set to TRUE if at query execution time we determine that this item's
value is a constant during this execution. We need this member because
it is not possible to substitute 'this' with a constant item.
*/
bool is_constant;
/*
expr & optimizer used in subselect rewriting to store Item for
@ -387,8 +393,8 @@ public:
Item_in_subselect(Item * left_expr, st_select_lex *select_lex);
Item_in_subselect()
:Item_exists_subselect(), left_expr_cache(0), first_execution(TRUE),
optimizer(0), abort_on_null(0), pushed_cond_guards(NULL),
exec_method(NOT_TRANSFORMED), upper_item(0)
is_constant(FALSE), optimizer(0), abort_on_null(0),
pushed_cond_guards(NULL), exec_method(NOT_TRANSFORMED), upper_item(0)
{}
void cleanup();
subs_type substype() { return IN_SUBS; }
@ -421,6 +427,8 @@ public:
void update_used_tables();
bool setup_engine();
bool init_left_expr_cache();
/* Inform 'this' that it was computed, and contains a valid result. */
void set_first_execution() { if (first_execution) first_execution= FALSE; }
bool is_expensive_processor(uchar *arg);
friend class Item_ref_null_helper;
@ -428,6 +436,7 @@ public:
friend class Item_in_optimizer;
friend class subselect_indexsubquery_engine;
friend class subselect_hash_sj_engine;
friend class subselect_rowid_merge_engine;
};
@ -462,7 +471,8 @@ public:
enum enum_engine_type {ABSTRACT_ENGINE, SINGLE_SELECT_ENGINE,
UNION_ENGINE, UNIQUESUBQUERY_ENGINE,
INDEXSUBQUERY_ENGINE, HASH_SJ_ENGINE};
INDEXSUBQUERY_ENGINE, HASH_SJ_ENGINE,
ROR_INTERSECT_ENGINE};
subselect_engine(Item_subselect *si, select_result_interceptor *res)
:thd(0)
@ -635,8 +645,10 @@ public:
virtual void print (String *str, enum_query_type query_type);
bool change_result(Item_subselect *si, select_result_interceptor *result);
bool no_tables();
int index_lookup(); /* TIMOUR: this method needs refactoring. */
int scan_table();
bool copy_ref_key();
int copy_ref_key_simple(); /* TIMOUR: this method needs refactoring. */
bool no_rows() { return empty_result_set; }
virtual enum_engine_type engine_type() { return UNIQUESUBQUERY_ENGINE; }
};
@ -704,51 +716,399 @@ inline bool Item_subselect::is_uncacheable() const
}
/**
Compute an IN predicate via a hash semi-join. The subquery is materialized
during the first evaluation of the IN predicate. The IN predicate is executed
via the functionality inherited from subselect_uniquesubquery_engine.
/*
Distinguish the type od (0-based) row numbers from the type of the index into
an array of row numbers.
*/
typedef ha_rows rownum_t;
/*
An Ordered_key is an in-memory table index that allows O(log(N)) time
lookups of a multi-part key.
If the index is over a single column, then this column may contain NULLs, and
the NULLs are stored and tested separately for NULL in O(1) via is_null().
Multi-part indexes assume that the indexed columns do not contain NULLs.
TODO:
= Due to the unnatural assymetry between single and multi-part indexes, it
makes sense to somehow refactor or extend the class.
= This class can be refactored into a base abstract interface, and two
subclasses:
- one to represent single-column indexes, and
- another to represent multi-column indexes.
Such separation would allow slightly more efficient implementation of
the single-column indexes.
= The current design requires such indexes to be fully recreated for each
PS (re)execution, however most of the comprising objects can be reused.
*/
class subselect_hash_sj_engine: public subselect_uniquesubquery_engine
class Ordered_key
{
protected:
/*
Index of the key in an array of keys. This index allows to
construct (sub)sets of keys represented by bitmaps.
*/
uint key_idx;
/* The table being indexed. */
TABLE *tbl;
/* The columns being indexed. */
Item_field **key_columns;
/* Number of elements in 'key_columns' (number of key parts). */
uint key_column_count;
/*
An expression, or sequence of expressions that forms the search key.
*/
Item *search_key;
/* Value index related members. */
/*
The actual value index, consists of a sorted sequence of row numbers.
*/
rownum_t *key_buff;
/* Number of elements in key_buff. */
ha_rows key_buff_elements;
/* Current element in 'key_buff'. */
ha_rows cur_key_idx;
/*
Mapping from row numbers to row ids. The element row_num_to_rowid[i]
contains a buffer with the rowid for the row numbered 'i'.
The memory for this member is not maintanined by this class because
all Ordered_key indexes of the same table share the same mapping.
*/
uchar *row_num_to_rowid;
/*
A sequence of predicates to compare the search key with the corresponding
columns of a table row from the index.
*/
Item_func_lt **compare_pred;
/* Null index related members. */
MY_BITMAP null_key;
/* Count of NULLs per column. */
ha_rows null_count;
/* The row number that contains the first NULL in a column. */
ha_rows min_null_row;
/* The row number that contains the last NULL in a column. */
ha_rows max_null_row;
protected:
bool alloc_keys_buffers();
/*
Quick sort comparison function that compares two rows of the same table
indentfied with their row numbers.
*/
int cmp_keys_by_row_data(rownum_t a, rownum_t b);
static int cmp_keys_by_row_data_and_rownum(Ordered_key *key,
rownum_t* a, rownum_t* b);
int cmp_key_with_search_key(rownum_t row_num);
public:
static void *operator new(size_t size) throw ()
{ return sql_alloc(size); }
Ordered_key(uint key_idx_arg, TABLE *tbl_arg,
Item *search_key_arg, ha_rows null_count_arg,
ha_rows min_null_row_arg, ha_rows max_null_row_arg,
uchar *row_num_to_rowid_arg);
~Ordered_key();
void cleanup();
/* Initialize a multi-column index. */
bool init(MY_BITMAP *columns_to_index);
/* Initialize a single-column index. */
bool init(int col_idx);
uint get_column_count() { return key_column_count; }
uint get_key_idx() { return key_idx; }
uint get_field_idx(uint i)
{
DBUG_ASSERT(i < key_column_count);
return key_columns[i]->field->field_index;
}
Item *get_search_key(uint i)
{
return search_key->element_index(key_columns[i]->field->field_index);
}
void add_key(rownum_t row_num)
{
/* The caller must know how many elements to add. */
DBUG_ASSERT(key_buff_elements && cur_key_idx < key_buff_elements);
key_buff[cur_key_idx]= row_num;
++cur_key_idx;
}
void sort_keys();
double null_selectivity() { return (1 - null_count / null_key.n_bits); }
/*
Position the current element at the first row that matches the key.
The key itself is propagated by evaluating the current value(s) of
this->search_key.
*/
bool lookup();
/* Move the current index cursor to the first key. */
void first()
{
DBUG_ASSERT(key_buff_elements);
cur_key_idx= 0;
}
/* TODO */
bool next_same();
/* Move the current index cursor to the next key. */
bool next()
{
DBUG_ASSERT(key_buff_elements);
if (cur_key_idx < key_buff_elements - 1)
{
++cur_key_idx;
return TRUE;
}
return FALSE;
};
/* Return the current index element. */
rownum_t current()
{
DBUG_ASSERT(key_buff_elements && cur_key_idx < key_buff_elements);
return key_buff[cur_key_idx];
}
void set_null(rownum_t row_num)
{
bitmap_set_bit(&null_key, row_num);
}
bool is_null(rownum_t row_num)
{
/*
Indexes consisting of only NULLs do not have a bitmap buffer at all.
Their only initialized member is 'n_bits', which is equal to the number
of temp table rows.
*/
if (null_count == tbl->file->stats.records)
{
DBUG_ASSERT(tbl->file->stats.records == null_key.n_bits);
return TRUE;
}
if (row_num > max_null_row || row_num < min_null_row)
return FALSE;
return bitmap_is_set(&null_key, row_num);
}
};
class subselect_rowid_merge_engine: public subselect_engine
{
protected:
/* The temporary table that contains a materialized subquery. */
TABLE *tmp_table;
/*
The engine used to check whether an IN predicate is TRUE or not. If not
TRUE, then subselect_rowid_merge_engine further distinguishes between
FALSE and UNKNOWN.
*/
subselect_uniquesubquery_engine *lookup_engine;
/*
Mapping from row numbers to row ids. The rowids are stored sequentially
in the array - rowid[i] is located in row_num_to_rowid + i * rowid_length.
*/
uchar *row_num_to_rowid;
/*
A subset of all the keys for which there is a match for the same row.
Used during execution. Computed for each outer reference
*/
MY_BITMAP matching_keys;
/*
The columns of the outer reference that are NULL. Computed for each
outer reference.
*/
MY_BITMAP matching_outer_cols;
/*
Columns that consist of only NULLs. Such columns match any value.
Computed once per query execution.
*/
MY_BITMAP null_only_columns;
/*
Indexes of row numbers, sorted by <column_value, row_number>. If an
index may contain NULLs, the NULLs are stored efficiently in a bitmap.
The indexes are sorted by the selectivity of their NULL sub-indexes, the
one with the fewer NULLs is first. Thus, if there is any index on
non-NULL columns, it is contained in keys[0].
*/
Ordered_key **merge_keys;
/* The number of elements in keys. */
uint keys_count;
/*
An index on all non-NULL columns of 'tmp_table'. The index has the
logical form: <[v_i1 | ... | v_ik], rownum>. It allows to find the row
number where the columns c_i1,...,c1_k contain the values v_i1,...,v_ik.
If such an index exists, it is always the first element of 'keys'.
*/
Ordered_key *non_null_key;
/*
Priority queue of Ordered_key indexes, one per NULLable column.
This queue is used by the partial match algorithm in method exec().
*/
QUEUE pq;
/* True if there is a NULL (sub)row that covers all NULLable columns. */
bool has_covering_null_row;
protected:
/*
Comparison function to compare keys in order of increasing bitmap
selectivity.
*/
static int cmp_keys_by_null_selectivity(Ordered_key *a, Ordered_key *b);
/*
Comparison function used by the priority queue pq, the 'smaller' key
is the one with the smaller current row number.
*/
static int cmp_keys_by_cur_rownum(void *arg, uchar *k1, uchar *k2);
bool test_null_row(rownum_t row_num);
bool partial_match();
public:
subselect_rowid_merge_engine(subselect_uniquesubquery_engine *engine_arg,
TABLE *tmp_table_arg, uint keys_count_arg,
uint has_covering_null_row_arg,
Item_subselect *item_arg,
select_result_interceptor *result_arg)
:subselect_engine(item_arg, result_arg),
tmp_table(tmp_table_arg), lookup_engine(engine_arg),
keys_count(keys_count_arg), non_null_key(NULL),
has_covering_null_row(has_covering_null_row_arg)
{
thd= lookup_engine->get_thd();
}
~subselect_rowid_merge_engine();
bool init(MY_BITMAP *non_null_key_parts, MY_BITMAP *partial_match_key_parts);
void cleanup();
int prepare() { return 0; }
void fix_length_and_dec(Item_cache**) {}
int exec();
uint cols() { /* TODO: what is the correct value? */ return 1; }
uint8 uncacheable() { return UNCACHEABLE_DEPENDENT; }
void exclude() {}
table_map upper_select_const_tables() { return 0; }
void print(String*, enum_query_type) {}
bool change_result(Item_subselect*, select_result_interceptor*)
{ DBUG_ASSERT(FALSE); return false; }
bool no_tables() { return false; }
bool no_rows()
{
/*
TODO: It is completely unclear what is the semantics of this
method. The current result is computed so that the call to no_rows()
from Item_in_optimizer::val_int() sets Item_in_optimizer::null_value
correctly.
*/
return !(((Item_in_subselect *) item)->null_value);
}
};
/**
Compute an IN predicate via a hash semi-join. This class is responsible for
the materialization of the subquery, and the selection of the correct and
optimal execution method (e.g. direct index lookup, or partial matching) for
the IN predicate.
*/
class subselect_hash_sj_engine : public subselect_engine
{
protected:
/* The table into which the subquery is materialized. */
TABLE *tmp_table;
/* TRUE if the subquery was materialized into a temp table. */
bool is_materialized;
/*
The old engine already chosen at parse time and stored in permanent memory.
Through this member we can re-create and re-prepare materialize_join for
each execution of a prepared statement. We akso resuse the functionality
each execution of a prepared statement. We also reuse the functionality
of subselect_single_select_engine::[prepare | cols].
*/
subselect_single_select_engine *materialize_engine;
/* The engine used to compute the IN predicate. */
subselect_engine *lookup_engine;
/*
QEP to execute the subquery and materialize its result into a
temporary table. Created during the first call to exec().
*/
JOIN *materialize_join;
/* Temp table context of the outer select's JOIN. */
TMP_TABLE_PARAM *tmp_param;
/*
TRUE if the subquery result has an all-NULL column, which means that
there at best can be a partial match for any IN execution.
*/
bool inner_partial_match;
/*
TRUE if the materialized subquery contains a whole row only of NULLs.
*/
bool has_null_row;
/* Keyparts of the only non-NULL composite index in a rowid merge. */
MY_BITMAP non_null_key_parts;
/* Keyparts of the single column indexes with NULL, one keypart per index. */
MY_BITMAP partial_match_key_parts;
uint count_partial_match_columns;
uint count_null_only_columns;
/*
A conjunction of all the equality condtions between all pairs of expressions
that are arguments of an IN predicate. We need these to post-filter some
IN results because index lookups sometimes match values that are actually
not equal to the search key in SQL terms.
*/
Item *semi_join_conds;
/* Possible execution strategies that can be used to compute hash semi-join.*/
enum exec_strategy {
COMPLETE_MATCH, /* Use regular index lookups. */
PARTIAL_MATCH, /* Use some partial matching strategy. */
PARTIAL_MATCH_INDEX, /* Use partial matching through index merging. */
PARTIAL_MATCH_SCAN, /* Use partial matching through table scan. */
IMPOSSIBLE /* Subquery materialization is not applicable. */
};
/* The chosen execution strategy. Computed after materialization. */
exec_strategy strategy;
protected:
void set_strategy_using_schema();
void set_strategy_using_data();
bool make_semi_join_conds();
subselect_uniquesubquery_engine* make_unique_engine();
public:
subselect_hash_sj_engine(THD *thd, Item_subselect *in_predicate,
subselect_single_select_engine *old_engine)
:subselect_uniquesubquery_engine(thd, NULL, in_predicate, NULL),
is_materialized(FALSE), materialize_engine(old_engine),
materialize_join(NULL), tmp_param(NULL)
{}
subselect_single_select_engine *old_engine)
:subselect_engine(in_predicate, NULL), tmp_table(NULL),
is_materialized(FALSE), materialize_engine(old_engine), lookup_engine(NULL),
materialize_join(NULL), count_partial_match_columns(0),
count_null_only_columns(0), semi_join_conds(NULL)
{
set_thd(thd);
}
~subselect_hash_sj_engine();
bool init_permanent(List<Item> *tmp_columns);
bool init_runtime();
void cleanup();
int prepare() { return 0; }
int prepare() { return 0; } /* Override virtual function in base class. */
int exec();
virtual void print (String *str, enum_query_type query_type);
uint cols()
{
return materialize_engine->cols();
}
uint8 uncacheable() { return UNCACHEABLE_DEPENDENT; }
table_map upper_select_const_tables() { return 0; }
bool no_rows() { return !tmp_table->file->stats.records; }
virtual enum_engine_type engine_type() { return HASH_SJ_ENGINE; }
/*
TODO: factor out all these methods in a base subselect_index_engine class
because all of them have dummy implementations and should never be called.
*/
void fix_length_and_dec(Item_cache** row);//=>base class
void exclude(); //=>base class
//=>base class
bool change_result(Item_subselect *si, select_result_interceptor *result);
bool no_tables();//=>base class
};

13
sql/opt_subselect.cc
View file

@ -187,11 +187,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
does not call setup_subquery_materialization(). We could make
SELECT ... FROM DUAL call that function but that doesn't seem
to be the case that is worth handling.
4. Subquery predicate is a top-level predicate
(this implies it is not negated)
TODO: this is a limitation that should be lifted once we
implement correct NULL semantics (WL#3830)
5. Subquery is non-correlated
4. Subquery is non-correlated
TODO:
This is an overly restrictive condition. It can be extended to:
(Subquery is non-correlated ||
@ -199,7 +195,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
(Subquery is correlated to the immediate outer query &&
Subquery !contains {GROUP BY, ORDER BY [LIMIT],
aggregate functions}) && subquery predicate is not under "NOT IN"))
6. No execution method was already chosen (by a prepared statement).
5. No execution method was already chosen (by a prepared statement).
(*) The subquery must be part of a SELECT statement. The current
condition also excludes multi-table update statements.
@ -218,9 +214,8 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
subquery_types_allow_materialization(in_subs))
{
// psergey-todo: duplicated_subselect_card_check: where it's done?
if (in_subs->is_top_level_item() && // 4
!in_subs->is_correlated && // 5
in_subs->exec_method == Item_in_subselect::NOT_TRANSFORMED) // 6
if (!in_subs->is_correlated && // 4
in_subs->exec_method == Item_in_subselect::NOT_TRANSFORMED) // 5
in_subs->exec_method= Item_in_subselect::MATERIALIZATION;
}

66
sql/sql_class.cc
View file

@ -42,6 +42,7 @@
#include "sp_rcontext.h"
#include "sp_cache.h"
#include "sql_select.h" /* declares create_tmp_table() */
/*
The following is used to initialise Table_ident with a internal
@ -2877,6 +2878,71 @@ bool select_dumpvar::send_eof()
return 0;
}
bool
select_materialize_with_stats::
create_result_table(THD *thd_arg, List<Item> *column_types,
bool is_union_distinct, ulonglong options,
const char *table_alias, bool bit_fields_as_long)
{
DBUG_ASSERT(table == 0);
tmp_table_param.field_count= column_types->elements;
tmp_table_param.bit_fields_as_long= bit_fields_as_long;
if (! (table= create_tmp_table(thd_arg, &tmp_table_param, *column_types,
(ORDER*) 0, is_union_distinct, 1,
options, HA_POS_ERROR, (char*) table_alias)))
return TRUE;
col_stat= (Column_statistics*) table->in_use->alloc(table->s->fields *
sizeof(Column_statistics));
if (!stat)
return TRUE;
cleanup();
table->file->extra(HA_EXTRA_WRITE_CACHE);
table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
return FALSE;
}
/**
Override select_union::send_data to analyze each row for NULLs and to
update null_statistics before sending data to the client.
@return TRUE if fatal error when sending data to the client
@return FALSE on success
*/
bool select_materialize_with_stats::send_data(List<Item> &items)
{
List_iterator_fast<Item> item_it(items);
Item *cur_item;
Column_statistics *cur_col_stat= col_stat;
uint nulls_in_row= 0;
++count_rows;
while ((cur_item= item_it++))
{
if (cur_item->is_null())
{
++cur_col_stat->null_count;
cur_col_stat->max_null_row= count_rows;
if (!cur_col_stat->min_null_row)
cur_col_stat->min_null_row= count_rows;
++nulls_in_row;
}
++cur_col_stat;
}
if (nulls_in_row > max_nulls_in_row)
max_nulls_in_row= nulls_in_row;
return select_union::send_data(items);
}
/****************************************************************************
TMP_TABLE_PARAM
****************************************************************************/

77
sql/sql_class.h
View file

@ -2740,19 +2740,20 @@ public:
class select_union :public select_result_interceptor
{
protected:
TMP_TABLE_PARAM tmp_table_param;
public:
TABLE *table;
select_union() :table(0) {}
select_union() :table(0) { tmp_table_param.init(); }
int prepare(List<Item> &list, SELECT_LEX_UNIT *u);
bool send_data(List<Item> &items);
bool send_eof();
bool flush();
bool create_result_table(THD *thd, List<Item> *column_types,
bool is_distinct, ulonglong options,
const char *alias, bool bit_fields_as_long);
virtual bool create_result_table(THD *thd, List<Item> *column_types,
bool is_distinct, ulonglong options,
const char *alias, bool bit_fields_as_long);
};
/* Base subselect interface class */
@ -2776,6 +2777,74 @@ public:
bool send_data(List<Item> &items);
};
/*
This class specializes select_union to collect statistics about the
data stored in the temp table. Currently the class collects statistcs
about NULLs.
*/
class select_materialize_with_stats : public select_union
{
protected:
class Column_statistics
{
public:
/* Count of NULLs per column. */
ha_rows null_count;
/* The row number that contains the first NULL in a column. */
ha_rows min_null_row;
/* The row number that contains the last NULL in a column. */
ha_rows max_null_row;
};
/* Array of statistics data per column. */
Column_statistics* col_stat;
/*
The number of columns in the biggest sub-row that consists of only
NULL values.
*/
ha_rows max_nulls_in_row;
/*
Count of rows writtent to the temp table. This is redundant as it is
already stored in handler::stats.records, however that one is relatively
expensive to compute (given we need that for evry row).
*/
ha_rows count_rows;
public:
select_materialize_with_stats() {}
virtual bool create_result_table(THD *thd, List<Item> *column_types,
bool is_distinct, ulonglong options,
const char *alias, bool bit_fields_as_long);
bool init_result_table(ulonglong select_options);
bool send_data(List<Item> &items);
void cleanup()
{
memset(col_stat, 0, table->s->fields * sizeof(Column_statistics));
max_nulls_in_row= 0;
count_rows= 0;
}
ha_rows get_null_count_of_col(uint idx)
{
DBUG_ASSERT(idx < table->s->fields);
return col_stat[idx].null_count;
}
ha_rows get_max_null_of_col(uint idx)
{
DBUG_ASSERT(idx < table->s->fields);
return col_stat[idx].max_null_row;
}
ha_rows get_min_null_of_col(uint idx)
{
DBUG_ASSERT(idx < table->s->fields);
return col_stat[idx].min_null_row;
}
ha_rows get_max_nulls_in_row() { return max_nulls_in_row; }
};
/* used in independent ALL/ANY optimisation */
class select_max_min_finder_subselect :public select_subselect
{

7
sql/sql_select.cc
View file

@ -874,6 +874,9 @@ JOIN::optimize()
{
DBUG_PRINT("info",("No tables"));
error= 0;
/* Create all structures needed for materialized subquery execution. */
if (setup_subquery_materialization())
DBUG_RETURN(1);
DBUG_RETURN(0);
}
error= -1; // Error is sent to client
@ -11233,7 +11236,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
param->group_buff=group_buff;
share->keys=1;
share->uniques= test(using_unique_constraint);
table->key_info=keyinfo;
table->key_info= table->s->key_info= keyinfo;
keyinfo->key_part=key_part_info;
keyinfo->flags=HA_NOSAME;
keyinfo->usable_key_parts=keyinfo->key_parts= param->group_parts;
@ -11319,7 +11322,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
keyinfo->key_parts * sizeof(KEY_PART_INFO))))
goto err;
bzero((void*) key_part_info, keyinfo->key_parts * sizeof(KEY_PART_INFO));
table->key_info=keyinfo;
table->key_info= table->s->key_info= keyinfo;
keyinfo->key_part=key_part_info;
keyinfo->flags=HA_NOSAME | HA_NULL_ARE_EQUAL;
keyinfo->key_length= 0; // Will compute the sum of the parts below.