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

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.
parent 02c4cab3
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sql/item_cmpfunc.h
View file @ a292ca34
......@@ -350,6 +350,7 @@ class Item_bool_func2 :public Item_int_func
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;
};
......
sql/item_subselect.cc
View file @ a292ca34
......@@ -138,6 +138,7 @@ void Item_in_subselect::cleanup()
left_expr_cache= NULL;
}
first_execution= TRUE;
is_constant= FALSE;
Item_subselect::cleanup();
DBUG_VOID_RETURN;
}
......@@ -438,8 +439,10 @@ bool Item_subselect::exec()
int res;
if (thd->is_error())
{
/* Do not execute subselect in case of a fatal error */
return 1;
}
/*
Simulate a failure in sub-query execution. Used to test e.g.
out of memory or query being killed conditions.
......@@ -464,9 +467,6 @@ bool Item_subselect::exec()
bool Item_in_subselect::exec()
{
DBUG_ENTER("Item_in_subselect::exec");
DBUG_ASSERT(exec_method != MATERIALIZATION ||
(exec_method == MATERIALIZATION &&
engine->engine_type() == subselect_engine::HASH_SJ_ENGINE));
/*
Initialize the cache of the left predicate operand. This has to be done as
late as now, because Cached_item directly contains a resolved field (not
......@@ -482,14 +482,14 @@ bool Item_in_subselect::exec()
if (!left_expr_cache && exec_method == MATERIALIZATION)
init_left_expr_cache();
/* If the new left operand is already in the cache, reuse the old result. */
if (left_expr_cache && test_if_item_cache_changed(*left_expr_cache) < 0)
{
/* Always compute IN for the first row as the cache is not valid for it. */
if (!first_execution)
/*
If the new left operand is already in the cache, reuse the old result.
Use the cached result only if this is not the first execution of IN
because the cache is not valid for the first execution.
*/
if (!first_execution && left_expr_cache &&
test_if_item_cache_changed(*left_expr_cache) < 0)
DBUG_RETURN(FALSE);
first_execution= FALSE;
}
/*
The exec() method below updates item::value, and item::null_value, thus if
......@@ -899,8 +899,8 @@ bool Item_in_subselect::test_limit(st_select_lex_unit *unit_arg)
Item_in_subselect::Item_in_subselect(Item * left_exp,
st_select_lex *select_lex):
Item_exists_subselect(), left_expr_cache(0), first_execution(TRUE),
optimizer(0), pushed_cond_guards(NULL), exec_method(NOT_TRANSFORMED),
upper_item(0)
is_constant(FALSE), optimizer(0), pushed_cond_guards(NULL),
exec_method(NOT_TRANSFORMED), upper_item(0)
{
DBUG_ENTER("Item_in_subselect::Item_in_subselect");
left_expr= left_exp;
......@@ -1094,6 +1094,8 @@ bool Item_in_subselect::val_bool()
{
DBUG_ASSERT(fixed == 1);
null_value= 0;
if (is_constant)
return value;
if (exec())
{
reset();
......@@ -1560,9 +1562,9 @@ Item_in_subselect::row_value_transformer(JOIN *join)
DBUG_ENTER("Item_in_subselect::row_value_transformer");
// psergey: duplicated_subselect_card_check
if (select_lex->item_list.elements != left_expr->cols())
if (select_lex->item_list.elements != cols_num)
{
my_error(ER_OPERAND_COLUMNS, MYF(0), left_expr->cols());
my_error(ER_OPERAND_COLUMNS, MYF(0), cols_num);
DBUG_RETURN(RES_ERROR);
}
......@@ -1969,17 +1971,69 @@ void Item_in_subselect::print(String *str, enum_query_type query_type)
bool Item_in_subselect::fix_fields(THD *thd_arg, Item **ref)
{
bool result = 0;
uint outer_cols_num;
List<Item> *inner_cols;
if (exec_method == SEMI_JOIN)
return !( (*ref)= new Item_int(1));
if (thd_arg->lex->view_prepare_mode && left_expr && !left_expr->fixed)
result = left_expr->fix_fields(thd_arg, &left_expr);
/*
Check if the outer and inner IN operands match in those cases when we
will not perform IN=>EXISTS transformation. Currently this is when we
use subquery materialization.
The condition below is true when this method was called recursively from
inside JOIN::prepare for the JOIN object created by the call chain
Item_subselect::fix_fields -> subselect_single_select_engine::prepare,
which creates a JOIN object for the subquery and calls JOIN::prepare for
the JOIN of the subquery.
Notice that in some cases, this doesn't happen, and the check_cols()
test for each Item happens later in
Item_in_subselect::row_value_in_to_exists_transformer.
The reason for this mess is that our JOIN::prepare phase works top-down
instead of bottom-up, so we first do name resoluton and semantic checks
for the outer selects, then for the inner.
*/
if (engine &&
engine->engine_type() == subselect_engine::SINGLE_SELECT_ENGINE &&
((subselect_single_select_engine*)engine)->join)
{
outer_cols_num= left_expr->cols();
if (unit->is_union())
inner_cols= &(unit->types);
else
inner_cols= &(unit->first_select()->item_list);
if (outer_cols_num != inner_cols->elements)
{
my_error(ER_OPERAND_COLUMNS, MYF(0), outer_cols_num);
return TRUE;
}
if (outer_cols_num > 1)
{
List_iterator<Item> inner_col_it(*inner_cols);
Item *inner_col;
for (uint i= 0; i < outer_cols_num; i++)
{
inner_col= inner_col_it++;
if (inner_col->check_cols(left_expr->element_index(i)->cols()))
return TRUE;
}
}
}
if (thd_arg->lex->view_prepare_mode && left_expr && !left_expr->fixed &&
left_expr->fix_fields(thd_arg, &left_expr))
return TRUE;
if (Item_subselect::fix_fields(thd_arg, ref))
return TRUE;
fixed= TRUE;
return result || Item_subselect::fix_fields(thd_arg, ref);
return FALSE;
}
void Item_in_subselect::fix_after_pullout(st_select_lex *new_parent, Item **ref)
{
left_expr->fix_after_pullout(new_parent, &left_expr);
......@@ -2256,10 +2310,9 @@ bool subselect_union_engine::no_rows()
void subselect_uniquesubquery_engine::cleanup()
{
DBUG_ENTER("subselect_uniquesubquery_engine::cleanup");
/*
subselect_uniquesubquery_engine have not 'result' assigbed, so we do not
cleanup() it
*/
/* Tell handler we don't need the index anymore */
if (tab->table->file->inited)
tab->table->file->ha_index_end();
DBUG_VOID_RETURN;
}
......@@ -2280,7 +2333,7 @@ subselect_union_engine::subselect_union_engine(st_select_lex_unit *u,
Create and prepare the JOIN object that represents the query execution
plan for the subquery.
@detail
@details
This method is called from Item_subselect::fix_fields. For prepared
statements it is called both during the PREPARE and EXECUTE phases in the
following ways:
......@@ -2582,14 +2635,23 @@ int subselect_uniquesubquery_engine::scan_table()
for (;;)
{
error=table->file->ha_rnd_next(table->record[0]);
if (error && error != HA_ERR_END_OF_FILE)
if (error) {
if (error == HA_ERR_RECORD_DELETED)
{
error= report_error(table, error);
error= 0;
continue;
}
if (error == HA_ERR_END_OF_FILE)
{
error= 0;
break;
}
/* No more rows */
if (table->status)
else
{
error= report_error(table, error);
break;
}
}
if (!cond || cond->val_int())
{
......@@ -2699,6 +2761,56 @@ bool subselect_uniquesubquery_engine::copy_ref_key()
}
/*
@retval 1 A NULL was found in the outer reference, index lookup is
not applicable, the outer ref is unsusable as a lookup key,
use some other method to find a match.
@retval 0 The outer ref was copied into an index lookup key.
@retval -1 The outer ref cannot possibly match any row, IN is FALSE.
*/
/* TIMOUR: this method is a variant of copy_ref_key(), needs refactoring. */
int subselect_uniquesubquery_engine::copy_ref_key_simple()
{
for (store_key **copy= tab->ref.key_copy ; *copy ; copy++)
{
enum store_key::store_key_result store_res;
store_res= (*copy)->copy();
tab->ref.key_err= store_res;
/*
When there is a NULL part in the key we don't need to make index
lookup for such key thus we don't need to copy whole key.
If we later should do a sequential scan return OK. Fail otherwise.
See also the comment for the subselect_uniquesubquery_engine::exec()
function.
*/
null_keypart= (*copy)->null_key;
if (null_keypart)
return 1;
/*
Check if the error is equal to STORE_KEY_FATAL. This is not expressed
using the store_key::store_key_result enum because ref.key_err is a
boolean and we want to detect both TRUE and STORE_KEY_FATAL from the
space of the union of the values of [TRUE, FALSE] and
store_key::store_key_result.
TODO: fix the variable an return types.
*/
if (store_res == store_key::STORE_KEY_FATAL)
{
/*
Error converting the left IN operand to the column type of the right
IN operand.
*/
return -1;
}
}
return 0;
}
/*
Execute subselect
......@@ -2739,7 +2851,13 @@ int subselect_uniquesubquery_engine::exec()
/* TODO: change to use of 'full_scan' here? */
if (copy_ref_key())
{
/*
TIMOUR: copy_ref_key() == 1 means NULL result, not error, why return 1?
Check who reiles on this result.
*/
DBUG_RETURN(1);
}
if (table->status)
{
/*
......@@ -2780,6 +2898,54 @@ int subselect_uniquesubquery_engine::exec()
}
/*
TIMOUR: this needs more thinking, as exec() is a wrong IMO because:
- we don't need empty_result_set, as it is == 1 <=> when
item->value == 0
- scan_table() returns >0 even when there was no actuall error,
but we only found EOF while scanning.
- scan_table should not check table->status, but it should check
HA_ERR_END_OF_FILE
*/
int subselect_uniquesubquery_engine::index_lookup()
{
DBUG_ENTER("subselect_uniquesubquery_engine::index_lookup");
int error;
TABLE *table= tab->table;
empty_result_set= TRUE;
table->status= 0;
if (!table->file->inited)
table->file->ha_index_init(tab->ref.key, 0);
error= table->file->ha_index_read_map(table->record[0],
tab->ref.key_buff,
make_prev_keypart_map(tab->
ref.key_parts),
HA_READ_KEY_EXACT);
DBUG_PRINT("info", ("lookup result: %i", error));
if (error &&
error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
error= report_error(table, error);
else
{
error= 0;
table->null_row= 0;
if (!table->status && (!cond || cond->val_int()))
{
((Item_in_subselect *) item)->value= 1;
empty_result_set= FALSE;
}
else
((Item_in_subselect *) item)->value= 0;
}
DBUG_RETURN(error);
}
subselect_uniquesubquery_engine::~subselect_uniquesubquery_engine()
{
/* Tell handler we don't need the index anymore */
......@@ -3214,6 +3380,7 @@ bool subselect_union_engine::no_tables()
bool subselect_uniquesubquery_engine::no_tables()
{
/* returning value is correct, but this method should never be called */
DBUG_ASSERT(FALSE);
return 0;
}
......@@ -3223,17 +3390,140 @@ bool subselect_uniquesubquery_engine::no_tables()
******************************************************************************/
/**
Check if an IN predicate should be executed via partial matching using
only schema information.
@details
This test essentially has three results:
- partial matching is applicable, but cannot be executed due to a
limitation in the total number of indexes, as a result we can't
use subquery materialization at all.
- partial matching is either applicable or not, and this can be
determined by looking at 'this->max_keys'.
If max_keys > 1, then we need partial matching because there are
more indexes than just the one we use during materialization to
remove duplicates.
*/
void subselect_hash_sj_engine::set_strategy_using_schema()
{
Item_in_subselect *item_in= (Item_in_subselect *) item;
DBUG_ENTER("subselect_hash_sj_engine::set_strategy_using_schema");
if (item_in->is_top_level_item())
strategy= COMPLETE_MATCH;
else
{
List_iterator<Item> inner_col_it(*item_in->unit->get_unit_column_types());
Item *outer_col, *inner_col;
for (uint i= 0; i < item_in->left_expr->cols(); i++)
{
outer_col= item_in->left_expr->element_index(i);
inner_col= inner_col_it++;
if (!inner_col->maybe_null && !outer_col->maybe_null)
bitmap_set_bit(&non_null_key_parts, i);
else
{
bitmap_set_bit(&partial_match_key_parts, i);
++count_partial_match_columns;
}
}
}
/* If no column contains NULLs use regular hash index lookups. */
if (count_partial_match_columns)
strategy= PARTIAL_MATCH;
else
strategy= COMPLETE_MATCH;
DBUG_VOID_RETURN;
}
/**
Test whether an IN predicate must be computed via partial matching
based on the NULL statistics for each column of a materialized subquery.
@details The procedure analyzes column NULL statistics, updates the
matching type of columns that cannot be NULL or that contain only NULLs.
Based on this, the procedure determines the final execution strategy for
the [NOT] IN predicate.
*/
void subselect_hash_sj_engine::set_strategy_using_data()
{
Item_in_subselect *item_in= (Item_in_subselect *) item;
select_materialize_with_stats *result_sink=
(select_materialize_with_stats *) result;
Item *outer_col;
DBUG_ENTER("subselect_hash_sj_engine::set_strategy_using_data");
/* Call this procedure only if already selected partial matching. */
DBUG_ASSERT(strategy == PARTIAL_MATCH);
for (uint i= 0; i < item_in->left_expr->cols(); i++)
{
if (!bitmap_is_set(&partial_match_key_parts, i))
continue;
outer_col= item_in->left_expr->element_index(i);
/*
If column 'i' doesn't contain NULLs, and the corresponding outer reference
cannot have a NULL value, then 'i' is a non-nullable column.
*/
if (result_sink->get_null_count_of_col(i) == 0 && !outer_col->maybe_null)
{
bitmap_clear_bit(&partial_match_key_parts, i);
bitmap_set_bit(&non_null_key_parts, i);
--count_partial_match_columns;
}
if (result_sink->get_null_count_of_col(i) ==
tmp_table->file->stats.records)
++count_null_only_columns;
}
/* If no column contains NULLs use regular hash index lookups. */
if (!count_partial_match_columns)
strategy= COMPLETE_MATCH;
DBUG_VOID_RETURN;
}
/*
Initialize a MY_BITMAP with a buffer allocated on the current
memory root.
TIMOUR: move to bitmap C file?
*/
static my_bool
bitmap_init_memroot(MY_BITMAP *map, uint n_bits, MEM_ROOT *mem_root)
{
my_bitmap_map *bitmap_buf;
if (!(bitmap_buf= (my_bitmap_map*) alloc_root(mem_root,
bitmap_buffer_size(n_bits))) ||
bitmap_init(map, bitmap_buf, n_bits, FALSE))
return TRUE;
bitmap_clear_all(map);
return FALSE;
}
/**
Create all structures needed for IN execution that can live between PS
reexecution.
@detail
@param tmp_columns the items that produce the data for the temp table
@details
- Create a temporary table to store the result of the IN subquery. The
temporary table has one hash index on all its columns.
- Create a new result sink that sends the result stream of the subquery to
the temporary table,
- Create and initialize a new JOIN_TAB, and TABLE_REF objects to perform
lookups into the indexed temporary table.
@notice:
Currently Item_subselect::init() already chooses and creates at parse
......@@ -3245,166 +3535,228 @@ bool subselect_uniquesubquery_engine::no_tables()
bool subselect_hash_sj_engine::init_permanent(List<Item> *tmp_columns)
{
/* The result sink where we will materialize the subquery result. */
select_union *tmp_result_sink;
/* The table into which the subquery is materialized. */
TABLE *tmp_table;
KEY *tmp_key; /* The only index on the temporary table. */
uint tmp_key_parts; /* Number of keyparts in tmp_key. */
Item_in_subselect *item_in= (Item_in_subselect *) item;
/* Options to create_tmp_table. */
ulonglong tmp_create_options= thd->options | TMP_TABLE_ALL_COLUMNS;
/* | TMP_TABLE_FORCE_MYISAM; TIMOUR: force MYISAM */
DBUG_ENTER("subselect_hash_sj_engine::init_permanent");
/* 1. Create/initialize materialization related objects. */
if (bitmap_init_memroot(&non_null_key_parts, tmp_columns->elements,
thd->mem_root) ||
bitmap_init_memroot(&partial_match_key_parts, tmp_columns->elements,
thd->mem_root))
DBUG_RETURN(TRUE);
set_strategy_using_schema();
/*
Create and initialize a select result interceptor that stores the
result stream in a temporary table. The temporary table itself is
managed (created/filled/etc) internally by the interceptor.
*/
if (!(tmp_result_sink= new select_union))
/*
TIMOUR:
Select a more efficient result sink when we know there is no need to collect
data statistics.
if (strategy == COMPLETE_MATCH)
{
if (!(result= new select_union))
DBUG_RETURN(TRUE);
}
else if (strategy == PARTIAL_MATCH)
{
if (!(result= new select_materialize_with_stats))
DBUG_RETURN(TRUE);
}
*/
if (!(result= new select_materialize_with_stats))
DBUG_RETURN(TRUE);
if (tmp_result_sink->create_result_table(
thd, tmp_columns, TRUE,
thd->options | TMP_TABLE_ALL_COLUMNS,
if (((select_union*) result)->create_result_table(
thd, tmp_columns, TRUE, tmp_create_options,
"materialized subselect", TRUE))
DBUG_RETURN(TRUE);
tmp_table= tmp_result_sink->table;
tmp_key= tmp_table->key_info;
tmp_key_parts= tmp_key->key_parts;
tmp_table= ((select_union*) result)->table;
/*
If the subquery has blobs, or the total key lenght is bigger than some
length, then the created index cannot be used for lookups and we
can't use hash semi join. If this is the case, delete the temporary
table since it will not be used, and tell the caller we failed to
initialize the engine.
If the subquery has blobs, or the total key lenght is bigger than
some length, or the total number of key parts is more than the
allowed maximum (currently MAX_REF_PARTS == 16), then the created
index cannot be used for lookups and we can't use hash semi
join. If this is the case, delete the temporary table since it
will not be used, and tell the caller we failed to initialize the
engine.
*/
if (tmp_table->s->keys == 0)
{
#ifndef DBUG_OFF
handlerton *tmp_table_hton= tmp_table->s->db_type();
#ifdef USE_MARIA_FOR_TMP_TABLES
DBUG_ASSERT(tmp_table_hton == maria_hton);
#else
DBUG_ASSERT(tmp_table_hton == myisam_hton);
#endif
#endif
DBUG_ASSERT(
tmp_table->s->uniques ||
tmp_table->key_info->key_length >= tmp_table->file->max_key_length() ||
tmp_table->key_info->key_parts > tmp_table->file->max_key_parts());
free_tmp_table(thd, tmp_table);
tmp_table= NULL;
delete result;
result= NULL;
DBUG_RETURN(TRUE);
}
result= tmp_result_sink;
/*
Make sure there is only one index on the temp table, and it doesn't have
the extra key part created when s->uniques > 0.
*/
DBUG_ASSERT(tmp_table->s->keys == 1 && tmp_columns->elements == tmp_key_parts);
DBUG_ASSERT(tmp_table->s->keys == 1 &&
((Item_in_subselect *) item)->left_expr->cols() ==
tmp_table->key_info->key_parts);
/* 2. Create/initialize execution related objects. */
/*
Create and initialize the JOIN_TAB that represents an index lookup
plan operator into the materialized subquery result. Notice that:
- this JOIN_TAB has no corresponding JOIN (and doesn't need one), and
- here we initialize only those members that are used by
subselect_uniquesubquery_engine, so these objects are incomplete.
*/
if (!(tab= (JOIN_TAB*) thd->alloc(sizeof(JOIN_TAB))))
DBUG_RETURN(TRUE);
tab->table= tmp_table;
tab->ref.key= 0; /* The only temp table index. */
tab->ref.key_length= tmp_key->key_length;
if (!(tab->ref.key_buff=
(uchar*) thd->calloc(ALIGN_SIZE(tmp_key->key_length) * 2)) ||
!(tab->ref.key_copy=
(store_key**) thd->alloc((sizeof(store_key*) *
(tmp_key_parts + 1)))) ||
!(tab->ref.items=
(Item**) thd->alloc(sizeof(Item*) * tmp_key_parts)))
if (make_semi_join_conds())
DBUG_RETURN(TRUE);
KEY_PART_INFO *cur_key_part= tmp_key->key_part;
store_key **ref_key= tab->ref.key_copy;
uchar *cur_ref_buff= tab->ref.key_buff;
DBUG_RETURN(FALSE);
}
/*
/*
Create an artificial condition to post-filter those rows matched by index
lookups that cannot be distinguished by the index lookup procedure, e.g.
because of truncation. Prepared statements execution requires that
fix_fields is called for every execution. In order to call fix_fields we
need to create a Name_resolution_context and a corresponding TABLE_LIST
for the temporary table for the subquery, so that all column references
lookups that cannot be distinguished by the index lookup procedure.
@notes
The need for post-filtering may occur e.g. because of
truncation. Prepared statements execution requires that fix_fields is
called for every execution. In order to call fix_fields we need to
create a Name_resolution_context and a corresponding TABLE_LIST for
the temporary table for the subquery, so that all column references
to the materialized subquery table can be resolved correctly.
*/
DBUG_ASSERT(cond == NULL);
if (!(cond= new Item_cond_and))
DBUG_RETURN(TRUE);
@returns
@retval TRUE memory allocation error occurred
@retval FALSE the conditions were created and resolved (fixed)
*/
bool subselect_hash_sj_engine::make_semi_join_conds()
{
/*
Table reference for tmp_table that is used to resolve column references
(Item_fields) to columns in tmp_table.
*/
TABLE_LIST *tmp_table_ref;
/* Name resolution context for all tmp_table columns created below. */
Name_resolution_context *context;
Item_in_subselect *item_in= (Item_in_subselect *) item;
DBUG_ENTER("subselect_hash_sj_engine::make_semi_join_conds");
DBUG_ASSERT(semi_join_conds == NULL);
if (!(semi_join_conds= new Item_cond_and))
DBUG_RETURN(TRUE);
if (!(tmp_table_ref= (TABLE_LIST*) thd->alloc(sizeof(TABLE_LIST))))
DBUG_RETURN(TRUE);
tmp_table_ref->init_one_table("", "materialized subselect", TL_READ);
tmp_table_ref->table= tmp_table;
/* Name resolution context for all tmp_table columns created below. */
Name_resolution_context *context= new Name_resolution_context;
context= new Name_resolution_context;
context->init();
context->first_name_resolution_table=
context->last_name_resolution_table= tmp_table_ref;
for (uint i= 0; i < tmp_key_parts; i++, cur_key_part++, ref_key++)
for (uint i= 0; i < item_in->left_expr->cols(); i++)
{
Item_func_eq *eq_cond; /* New equi-join condition for the current column. */
/* Item for the corresponding field from the materialized temp table. */
Item_field *right_col_item;
int null_count= test(cur_key_part->field->real_maybe_null());
tab->ref.items[i]= item_in->left_expr->element_index(i);
if (!(right_col_item= new Item_field(thd, context, cur_key_part->field)) ||
!(eq_cond= new Item_func_eq(tab->ref.items[i], right_col_item)) ||
((Item_cond_and*)cond)->add(eq_cond))
if (!(right_col_item= new Item_field(thd, context, tmp_table->field[i])) ||
!(eq_cond= new Item_func_eq(item_in->left_expr->element_index(i),
right_col_item)) ||
(((Item_cond_and*)semi_join_conds)->add(eq_cond)))
{
delete cond;
cond= NULL;
delete semi_join_conds;
semi_join_conds= NULL;
DBUG_RETURN(TRUE);
}
*ref_key= new store_key_item(thd, cur_key_part->field,
/* TODO:
the NULL byte is taken into account in
cur_key_part->store_length, so instead of
cur_ref_buff + test(maybe_null), we could
use that information instead.
*/
cur_ref_buff + null_count,
null_count ? tab->ref.key_buff : 0,
cur_key_part->length, tab->ref.items[i]);
cur_ref_buff+= cur_key_part->store_length;
}
*ref_key= NULL; /* End marker. */
tab->ref.key_err= 1;
tab->ref.key_parts= tmp_key_parts;
if (cond->fix_fields(thd, &cond))
if (semi_join_conds->fix_fields(thd, &semi_join_conds))
DBUG_RETURN(TRUE);
DBUG_RETURN(FALSE);
}
/**
Create a new uniquesubquery engine for the execution of an IN predicate.
@details
Create and initialize a new JOIN_TAB, and Table_ref objects to perform
lookups into the indexed temporary table.
@retval A new subselect_hash_sj_engine object
@retval NULL if a memory allocation error occurs
*/
subselect_uniquesubquery_engine*
subselect_hash_sj_engine::make_unique_engine()
{
Item_in_subselect *item_in= (Item_in_subselect *) item;
/* The only index on the temporary table. */
KEY *tmp_key= tmp_table->key_info;
/* Number of keyparts in tmp_key. */
uint tmp_key_parts= tmp_key->key_parts;
JOIN_TAB *tab;
DBUG_ENTER("subselect_hash_sj_engine::make_unique_engine");
/*
Create and initialize the JOIN_TAB that represents an index lookup
plan operator into the materialized subquery result. Notice that:
- this JOIN_TAB has no corresponding JOIN (and doesn't need one), and
- here we initialize only those members that are used by
subselect_uniquesubquery_engine, so these objects are incomplete.
*/
if (!(tab= (JOIN_TAB*) thd->alloc(sizeof(JOIN_TAB))))
DBUG_RETURN(NULL);
tab->table= tmp_table;
tab->ref.key= 0; /* The only temp table index. */
tab->ref.key_length= tmp_key->key_length;
if (!(tab->ref.key_buff=
(uchar*) thd->calloc(ALIGN_SIZE(tmp_key->key_length) * 2)) ||
!(tab->ref.key_copy=
(store_key**) thd->alloc((sizeof(store_key*) *
(tmp_key_parts + 1)))) ||
!(tab->ref.items=
(Item**) thd->alloc(sizeof(Item*) * tmp_key_parts)))
DBUG_RETURN(NULL);
KEY_PART_INFO *cur_key_part= tmp_key->key_part;
store_key **ref_key= tab->ref.key_copy;
uchar *cur_ref_buff= tab->ref.key_buff;
for (uint i= 0; i < tmp_key_parts; i++, cur_key_part++, ref_key++)
{
tab->ref.items[i]= item_in->left_expr->element_index(i);
int null_count= test(cur_key_part->field->real_maybe_null());
*ref_key= new store_key_item(thd, cur_key_part->field,
/* TIMOUR:
the NULL byte is taken into account in
cur_key_part->store_length, so instead of
cur_ref_buff + test(maybe_null), we could
use that information instead.
*/
cur_ref_buff + null_count,
null_count ? tab->ref.key_buff : 0,
cur_key_part->length, tab->ref.items[i]);
cur_ref_buff+= cur_key_part->store_length;
}
*ref_key= NULL; /* End marker. */
tab->ref.key_err= 1;
tab->ref.key_parts= tmp_key_parts;
DBUG_RETURN(new subselect_uniquesubquery_engine(thd, tab, item,
semi_join_conds));
}
/**
Initialize members of the engine that need to be re-initilized at each
execution.
......@@ -3424,7 +3776,8 @@ bool subselect_hash_sj_engine::init_runtime()
Repeat name resolution for 'cond' since cond is not part of any
clause of the query, and it is not 'fixed' during JOIN::prepare.
*/
if (cond && !cond->fixed && cond->fix_fields(thd, &cond))
if (semi_join_conds && !semi_join_conds->fixed &&
semi_join_conds->fix_fields(thd, &semi_join_conds))
return TRUE;
/* Let our engine reuse this query plan for materialization. */
materialize_join= materialize_engine->join;
......@@ -3436,15 +3789,15 @@ bool subselect_hash_sj_engine::init_runtime()
subselect_hash_sj_engine::~subselect_hash_sj_engine()
{
delete result;
if (tab)
free_tmp_table(thd, tab->table);
if (tmp_table)
free_tmp_table(thd, tmp_table);
}
/**
Cleanup performed after each PS execution.
@detail
@details
Called in the end of JOIN::prepare for PS from Item_subselect::cleanup.
*/
......@@ -3453,14 +3806,13 @@ void subselect_hash_sj_engine::cleanup()
is_materialized= FALSE;
result->cleanup(); /* Resets the temp table as well. */
materialize_engine->cleanup();
subselect_uniquesubquery_engine::cleanup();
}
/**
Execute a subquery IN predicate via materialization.
@detail
@details
If needed materialize the subquery into a temporary table, then
copmpute the predicate via a lookup into this table.
......@@ -3471,6 +3823,8 @@ void subselect_hash_sj_engine::cleanup()
int subselect_hash_sj_engine::exec()
{
Item_in_subselect *item_in= (Item_in_subselect *) item;
SELECT_LEX *save_select= thd->lex->current_select;
int res= 0;
DBUG_ENTER("subselect_hash_sj_engine::exec");
......@@ -3478,10 +3832,6 @@ int subselect_hash_sj_engine::exec()
Optimize and materialize the subquery during the first execution of
the subquery predicate.
*/
if (!is_materialized)
{
int res= 0;
SELECT_LEX *save_select= thd->lex->current_select;
thd->lex->current_select= materialize_engine->select_lex;
if ((res= materialize_join->optimize()))
goto err; /* purecov: inspected */
......@@ -3505,29 +3855,75 @@ int subselect_hash_sj_engine::exec()
statistics, then we test if the temporary table for the query result is
empty.
*/
tab->table->file->info(HA_STATUS_VARIABLE);
if (!tab->table->file->stats.records)
tmp_table->file->info(HA_STATUS_VARIABLE);
if (!tmp_table->file->stats.records)
{
empty_result_set= TRUE;
item_in->value= FALSE;
/* TODO: check we need this: item_in->null_value= FALSE; */
/* The value of IN will not change during this execution. */
item_in->is_constant= TRUE;
item_in->set_first_execution();
/* TIMOUR: check if we need this: item_in->null_value= FALSE; */
DBUG_RETURN(FALSE);
}
/* Set tmp_param only if its usable, i.e. tmp_param->copy_field != NULL. */
tmp_param= &(item_in->unit->outer_select()->join->tmp_table_param);
if (tmp_param && !tmp_param->copy_field)
tmp_param= NULL;
if (strategy == PARTIAL_MATCH)
set_strategy_using_data();
/* A unique_engine is used both for complete and partial matching. */
if (!(lookup_engine= make_unique_engine()))
{
res= 1;
goto err;
}
if (strategy == PARTIAL_MATCH)
{
subselect_rowid_merge_engine *rowid_merge_engine;
uint count_pm_keys;
MY_BITMAP *nn_key_parts;
bool has_covering_null_row;
select_materialize_with_stats *result_sink=
(select_materialize_with_stats *) result;
/* Total number of keys needed for partial matching. */
nn_key_parts= (count_partial_match_columns < tmp_table->s->fields) ?
&non_null_key_parts : NULL;
has_covering_null_row= (result_sink->get_max_nulls_in_row() ==
tmp_table->s->fields -
(nn_key_parts ? bitmap_bits_set(nn_key_parts) : 0));
if (has_covering_null_row)
count_pm_keys= nn_key_parts ? 1 : 0;
else
count_pm_keys= count_partial_match_columns - count_null_only_columns +
(nn_key_parts ? 1 : 0);
if (!(rowid_merge_engine=
new subselect_rowid_merge_engine((subselect_uniquesubquery_engine*)
lookup_engine,
tmp_table,
count_pm_keys,
has_covering_null_row,
item, result)) ||
rowid_merge_engine->init(nn_key_parts, &partial_match_key_parts))
{
strategy= PARTIAL_MATCH_SCAN;
delete rowid_merge_engine;
/* TIMOUR: setup execution structures for partial match via scanning. */
}
else
{
strategy= PARTIAL_MATCH_INDEX;
lookup_engine= rowid_merge_engine;
}
}
item_in->change_engine(lookup_engine);
err:
thd->lex->current_select= save_select;
if (res)
DBUG_RETURN(res);
}
/*
Lookup the left IN operand in the hash index of the materialized subquery.
*/
DBUG_RETURN(subselect_uniquesubquery_engine::exec());
}
......@@ -3540,10 +3936,808 @@ void subselect_hash_sj_engine::print(String *str, enum_query_type query_type)
str->append(STRING_WITH_LEN(" <materialize> ("));
materialize_engine->print(str, query_type);
str->append(STRING_WITH_LEN(" ), "));
if (tab)
subselect_uniquesubquery_engine::print(str, query_type);
if (lookup_engine)
lookup_engine->print(str, query_type);
else
str->append(STRING_WITH_LEN(
"<the access method for lookups is not yet created>"
));
}
void subselect_hash_sj_engine::fix_length_and_dec(Item_cache** row)
{
DBUG_ASSERT(FALSE);
}
void subselect_hash_sj_engine::exclude()
{
DBUG_ASSERT(FALSE);
}
bool subselect_hash_sj_engine::no_tables()
{
DBUG_ASSERT(FALSE);
return FALSE;
}
bool subselect_hash_sj_engine::change_result(Item_subselect *si,
select_result_interceptor *res)
{
DBUG_ASSERT(FALSE);
return TRUE;
}
Ordered_key::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)
: key_idx(key_idx_arg), tbl(tbl_arg), search_key(search_key_arg),
row_num_to_rowid(row_num_to_rowid_arg), null_count(null_count_arg)
{
DBUG_ASSERT(tbl->file->stats.records > null_count);
key_buff_elements= tbl->file->stats.records - null_count;
cur_key_idx= HA_POS_ERROR;
DBUG_ASSERT((null_count && min_null_row_arg && max_null_row_arg) ||
(!null_count && !min_null_row_arg && !max_null_row_arg));
if (null_count)
{
/* The counters are 1-based, for key access we need 0-based indexes. */
min_null_row= min_null_row_arg - 1;
max_null_row= max_null_row_arg - 1;
}
else
min_null_row= max_null_row= 0;
}
Ordered_key::~Ordered_key()
{
/*
All data structures are allocated on thd->mem_root, thus we don't
free them here.
*/
}
/*
Cleanup that needs to be done for each PS (re)execution.
*/
void Ordered_key::cleanup()
{
/*
Currently these keys are recreated for each PS re-execution, thus
there is nothing to cleanup, the whole object goes away after execution
is over. All handler related initialization/deinitialization is done by
the parent subselect_rowid_merge_engine object.
*/
}
/*
Initialize a multi-column index.
*/
bool Ordered_key::init(MY_BITMAP *columns_to_index)
{
THD *thd= tbl->in_use;
uint cur_key_col= 0;
Item_field *cur_tmp_field;
Item_func_lt *fn_less_than;
key_column_count= bitmap_bits_set(columns_to_index);
// TIMOUR: check for mem allocation err, revert to scan
key_columns= (Item_field**) thd->alloc(key_column_count *
sizeof(Item_field*));
compare_pred= (Item_func_lt**) thd->alloc(key_column_count *
sizeof(Item_func_lt*));
for (uint i= 0; i < columns_to_index->n_bits; i++)
{
if (!bitmap_is_set(columns_to_index, i))
continue;
cur_tmp_field= new Item_field(tbl->field[i]);
/* Create the predicate (tmp_column[i] < outer_ref[i]). */
fn_less_than= new Item_func_lt(cur_tmp_field,
search_key->element_index(i));
fn_less_than->fix_fields(thd, (Item**) &fn_less_than);
key_columns[cur_key_col]= cur_tmp_field;
compare_pred[cur_key_col]= fn_less_than;
++cur_key_col;
}
if (alloc_keys_buffers())
{
/* TIMOUR revert to partial match via table scan. */
return TRUE;
}
return FALSE;
}
/*
Initialize a single-column index.
*/
bool Ordered_key::init(int col_idx)
{
THD *thd= tbl->in_use;
key_column_count= 1;
// TIMOUR: check for mem allocation err, revert to scan
key_columns= (Item_field**) thd->alloc(sizeof(Item_field*));
compare_pred= (Item_func_lt**) thd->alloc(sizeof(Item_func_lt*));
key_columns[0]= new Item_field(tbl->field[col_idx]);
/* Create the predicate (tmp_column[i] < outer_ref[i]). */
compare_pred[0]= new Item_func_lt(key_columns[0],
search_key->element_index(col_idx));
compare_pred[0]->fix_fields(thd, (Item**)&compare_pred[0]);
if (alloc_keys_buffers())
{
/* TIMOUR revert to partial match via table scan. */
return TRUE;
}
return FALSE;
}
bool Ordered_key::alloc_keys_buffers()
{
THD *thd= tbl->in_use;
DBUG_ASSERT(key_buff_elements > 0);
if (!(key_buff= (rownum_t*) thd->alloc(key_buff_elements *
sizeof(rownum_t))))
return TRUE;
/*
TIMOUR: it is enough to create bitmaps with size
(max_null_row - min_null_row), and then use min_null_row as
lookup offset.
*/
if (bitmap_init_memroot(&null_key,
/* this is max array index, we need count, so +1. */
max_null_row + 1,
thd->mem_root))
return TRUE;
cur_key_idx= HA_POS_ERROR;
return FALSE;
}
/*
Quick sort comparison function that compares two rows of the same table
indentfied with their row numbers.
@retval -1
@retval 0
@retval +1
*/
int
Ordered_key::cmp_keys_by_row_data(ha_rows a, ha_rows b)
{
uchar *rowid_a, *rowid_b;
int error, cmp_res;
/* The length in bytes of the rowids (positions) of tmp_table. */
uint rowid_length= tbl->file->ref_length;
if (a == b)
return 0;
/* Get the corresponding rowids. */
rowid_a= row_num_to_rowid + a * rowid_length;
rowid_b= row_num_to_rowid + b * rowid_length;
/* Fetch the rows for comparison. */
error= tbl->file->ha_rnd_pos(tbl->record[0], rowid_a);
DBUG_ASSERT(!error);
error= tbl->file->ha_rnd_pos(tbl->record[1], rowid_b);
DBUG_ASSERT(!error);
/*
Compare the two rows by the corresponding values of the indexed
columns.
*/
for (uint i= 0; i < key_column_count; i++)
{
Field *cur_field= key_columns[i]->field;
if ((cmp_res= cur_field->cmp_offset(tbl->s->rec_buff_length)))
return (cmp_res > 0 ? 1 : -1);
}
return 0;
}
int
Ordered_key::cmp_keys_by_row_data_and_rownum(Ordered_key *key,
rownum_t* a, rownum_t* b)
{
/* The result of comparing the two keys according to their row data. */
int cmp_row_res= key->cmp_keys_by_row_data(*a, *b);
if (cmp_row_res)
return cmp_row_res;
return (*a < *b) ? -1 : (*a > *b) ? 1 : 0;
}
void Ordered_key::sort_keys()
{
my_qsort2(key_buff, key_buff_elements, sizeof(rownum_t),
(qsort2_cmp) &cmp_keys_by_row_data_and_rownum, (void*) this);
/* Invalidate the current row position. */
cur_key_idx= HA_POS_ERROR;
}
/*
Compare the value(s) of the current key in 'search_key' with the
data of the current table record.
@notes The comparison result follows from the way compare_pred
is created in Ordered_key::init. Currently compare_pred compares
a field in of the current row with the corresponding Item that
contains the search key.
@param row_num Number of the row (not index in the key_buff array)
@retval -1 if (current row < search_key)
@retval 0 if (current row == search_key)
@retval +1 if (current row > search_key)
*/
int Ordered_key::cmp_key_with_search_key(rownum_t row_num)
{
/* The length in bytes of the rowids (positions) of tmp_table. */
uint rowid_length= tbl->file->ref_length;
uchar *cur_rowid= row_num_to_rowid + row_num * rowid_length;
int error, cmp_res;
error= tbl->file->ha_rnd_pos(tbl->record[0], cur_rowid);
DBUG_ASSERT(!error);
for (uint i= 0; i < key_column_count; i++)
{
cmp_res= compare_pred[i]->get_comparator()->compare();
/* Unlike Arg_comparator::compare_row() here there should be no NULLs. */
DBUG_ASSERT(!compare_pred[i]->null_value);
if (cmp_res)
return (cmp_res > 0 ? 1 : -1);
}
return 0;
}
/*
Find a key in a sorted array of keys via binary search.
see create_subq_in_equalities()
*/
bool Ordered_key::lookup()
{
DBUG_ASSERT(key_buff_elements);
ha_rows lo= 0;
ha_rows hi= key_buff_elements - 1;
ha_rows mid;
int cmp_res;
while (lo <= hi)
{
mid= lo + (hi - lo) / 2;
cmp_res= cmp_key_with_search_key(key_buff[mid]);
/*
In order to find the minimum match, check if the pevious element is
equal or smaller than the found one. If equal, we need to search further
to the left.
*/
if (!cmp_res && mid > 0)
cmp_res= !cmp_key_with_search_key(key_buff[mid - 1]) ? 1 : 0;
if (cmp_res == -1)
{
/* row[mid] < search_key */
lo= mid + 1;
}
else if (cmp_res == 1)
{
/* row[mid] > search_key */
if (!mid)
goto not_found;
hi= mid - 1;
}
else
{
/* row[mid] == search_key */
cur_key_idx= mid;
return TRUE;
}
}
not_found:
cur_key_idx= HA_POS_ERROR;
return FALSE;
}
/*
Move the current index pointer to the next key with the same column
values as the current key. Since the index is sorted, all such keys
are contiguous.
*/
bool Ordered_key::next_same()
{
DBUG_ASSERT(key_buff_elements);
if (cur_key_idx < key_buff_elements - 1)
{
/*
TIMOUR:
The below is quite inefficient, since as a result we will fetch every
row (except the last one) twice. There must be a more efficient way,
e.g. swapping record[0] and record[1], and reading only the new record.
*/
if (!cmp_keys_by_row_data(key_buff[cur_key_idx], key_buff[cur_key_idx + 1]))
{
++cur_key_idx;
return TRUE;
}
}
return FALSE;
}
/*
@param non_null_key_parts
@param partial_match_key_parts A union of all single-column NULL key parts.
@param count_partial_match_columns Number of NULL keyparts (set bits above).
*/
bool
subselect_rowid_merge_engine::init(MY_BITMAP *non_null_key_parts,
MY_BITMAP *partial_match_key_parts)
{
/* The length in bytes of the rowids (positions) of tmp_table. */
uint rowid_length= tmp_table->file->ref_length;
ha_rows row_count= tmp_table->file->stats.records;
rownum_t cur_rownum= 0;
select_materialize_with_stats *result_sink=
(select_materialize_with_stats *) result;
uint cur_key= 0;
Item_in_subselect *item_in= (Item_in_subselect*) item;
int error;
if (keys_count == 0)
{
/* There is nothing to initialize, we will only do regular lookups. */
return FALSE;
}
DBUG_ASSERT(!has_covering_null_row || (has_covering_null_row &&
keys_count == 1 &&
non_null_key_parts));
if (!(merge_keys= (Ordered_key**) thd->alloc(keys_count *
sizeof(Ordered_key*))) ||
!(row_num_to_rowid= (uchar*) thd->alloc(row_count * rowid_length *
sizeof(uchar))))
return TRUE;
/* Create the only non-NULL key if there is any. */
if (non_null_key_parts)
{
non_null_key= new Ordered_key(cur_key, tmp_table, item_in->left_expr,
0, 0, 0, row_num_to_rowid);
if (non_null_key->init(non_null_key_parts))
{
// TIMOUR: revert to partial matching via scanning
return TRUE;
}
merge_keys[cur_key]= non_null_key;
merge_keys[cur_key]->first();
++cur_key;
}
/*
If there is a covering NULL row, the only key that is needed is the
only non-NULL key that is already created above.
*/
if (!has_covering_null_row)
{
if (bitmap_init_memroot(&matching_keys, keys_count, thd->mem_root) ||
bitmap_init_memroot(&matching_outer_cols, keys_count, thd->mem_root) ||
bitmap_init_memroot(&null_only_columns, keys_count, thd->mem_root))
return TRUE;
/*
Create one single-column NULL-key for each column in
partial_match_key_parts.
*/
for (uint i= 0; i < partial_match_key_parts->n_bits; i++)
{
if (!bitmap_is_set(partial_match_key_parts, i))
continue;
if (result_sink->get_null_count_of_col(i) == row_count)
bitmap_set_bit(&null_only_columns, cur_key);
else
{
merge_keys[cur_key]= new Ordered_key(cur_key, tmp_table,
item_in->left_expr->element_index(i),
result_sink->get_null_count_of_col(i),
result_sink->get_min_null_of_col(i),
result_sink->get_max_null_of_col(i),
row_num_to_rowid);
if (merge_keys[cur_key]->init(i))
{
// TIMOUR: revert to partial matching via scanning
return TRUE;
}
merge_keys[cur_key]->first();
}
++cur_key;
}
}
/* Populate the indexes with data from the temporary table. */
tmp_table->file->ha_rnd_init(1);
tmp_table->file->extra_opt(HA_EXTRA_CACHE,
current_thd->variables.read_buff_size);
tmp_table->null_row= 0;
while (TRUE)
{
error= tmp_table->file->ha_rnd_next(tmp_table->record[0]);
if (error == HA_ERR_RECORD_DELETED)
{
/* We get this for duplicate records that should not be in tmp_table. */
continue;
}
/*
This is a temp table that we fully own, there should be no other
cause to stop the iteration than EOF.
*/
DBUG_ASSERT(!error || error == HA_ERR_END_OF_FILE);
if (error == HA_ERR_END_OF_FILE)
{
DBUG_ASSERT(cur_rownum == tmp_table->file->stats.records);
break;
}
/*
Save the position of this record in the row_num -> rowid mapping.
*/
tmp_table->file->position(tmp_table->record[0]);
memcpy(row_num_to_rowid + cur_rownum * rowid_length,
tmp_table->file->ref, rowid_length);
/* Add the current row number to the corresponding keys. */
if (non_null_key)
{
/* By definition there are no NULLs in the non-NULL key. */
non_null_key->add_key(cur_rownum);
}
for (uint i= (non_null_key ? 1 : 0); i < keys_count; i++)
{
/*
Check if the first and only indexed column contains NULL in the curent
row, and add the row number to the corresponding key.
*/
if (tmp_table->field[merge_keys[i]->get_field_idx(0)]->is_null())
merge_keys[i]->set_null(cur_rownum);
else
merge_keys[i]->add_key(cur_rownum);
}
++cur_rownum;
}
tmp_table->file->ha_rnd_end();
/* Sort the keys in each of the indexes. */
for (uint i= 0; i < keys_count; i++)
merge_keys[i]->sort_keys();
// TIMOUR: sort all the keys by NULL selectivity
if (init_queue(&pq, keys_count, 0, FALSE,
subselect_rowid_merge_engine::cmp_keys_by_cur_rownum, NULL))
{
// TIMOUR: revert to partial matching via scanning
return TRUE;
}
return FALSE;
}
subselect_rowid_merge_engine::~subselect_rowid_merge_engine()
{
delete_queue(&pq);
}
void subselect_rowid_merge_engine::cleanup()
{
lookup_engine->cleanup();
/* Tell handler we don't need the index anymore */
if (tmp_table->file->inited)
tmp_table->file->ha_rnd_end();
queue_remove_all(&pq);
}
/*
*/
int
subselect_rowid_merge_engine::cmp_keys_by_null_selectivity(Ordered_key *a,
Ordered_key *b)
{
double a_sel= a->null_selectivity();
double b_sel= b->null_selectivity();
if (a_sel == b_sel)
return 0;
if (a_sel > b_sel)
return 1;
return -1;
}
/*
*/
int
subselect_rowid_merge_engine::cmp_keys_by_cur_rownum(void *arg,
uchar *k1, uchar *k2)
{
rownum_t r1= ((Ordered_key*) k1)->current();
rownum_t r2= ((Ordered_key*) k2)->current();
return (r1 < r2) ? -1 : (r1 > r2) ? 1 : 0;
}
/*
Check if certain table row contains a NULL in all columns for which there is
no match in the corresponding value index.
@retval TRUE if a NULL row exists
@retval FALSE otherwise
*/
bool subselect_rowid_merge_engine::test_null_row(rownum_t row_num)
{
for (uint i = 0; i < keys_count; i++)
{
if (bitmap_is_set(&matching_keys, i))
{
/*
The key 'i' already matches a value in row 'row_num', thus we
skip it as it can't possibly match a NULL.
*/
continue;
}
if (!merge_keys[i]->is_null(row_num))
return FALSE;
}
return TRUE;
}
/*
@retval TRUE there is a partial match (UNKNOWN)
@retval FALSE there is no match at all (FALSE)
*/
bool subselect_rowid_merge_engine::partial_match()
{
Ordered_key *min_key; /* Key that contains the current minimum position. */
rownum_t min_row_num; /* Current row number of min_key. */
Ordered_key *cur_key;
rownum_t cur_row_num;
uint count_nulls_in_search_key= 0;
/* If there is a non-NULL key, it must be the first key in the keys array. */
DBUG_ASSERT(!non_null_key || (non_null_key && merge_keys[0] == non_null_key));
/* Check if there is a match for the columns of the only non-NULL key. */
if (non_null_key && !non_null_key->lookup())
return FALSE;
/*
If there is a NULL (sub)row that covers all NULL-able columns,
then there is a guranteed partial match, and we don't need to search
for the matching row.
*/
if (has_covering_null_row)
return TRUE;
if (non_null_key)
queue_insert(&pq, (uchar *) non_null_key);
/*
Do not add the non_null_key, since it was already processed above.
*/
bitmap_clear_all(&matching_outer_cols);
for (uint i= test(non_null_key); i < keys_count; i++)
{
DBUG_ASSERT(merge_keys[i]->get_column_count() == 1);
if (merge_keys[i]->get_search_key(0)->is_null())
{
++count_nulls_in_search_key;
bitmap_set_bit(&matching_outer_cols, merge_keys[i]->get_key_idx());
}
else if (merge_keys[i]->lookup())
queue_insert(&pq, (uchar *) merge_keys[i]);
}
/*
If the outer reference consists of only NULLs, or if it has NULLs in all
nullable columns, the result is UNKNOWN.
*/
if (count_nulls_in_search_key ==
((Item_in_subselect *) item)->left_expr->cols() -
(non_null_key ? non_null_key->get_column_count() : 0))
return TRUE;
/*
If there is no NULL (sub)row that covers all NULL columns, and there is no
single match for any of the NULL columns, the result is FALSE.
*/
if (pq.elements - test(non_null_key) == 0)
return FALSE;
DBUG_ASSERT(pq.elements);
min_key= (Ordered_key*) queue_remove(&pq, 0);
min_row_num= min_key->current();
bitmap_copy(&matching_keys, &null_only_columns);
bitmap_set_bit(&matching_keys, min_key->get_key_idx());
bitmap_union(&matching_keys, &matching_outer_cols);
if (min_key->next_same())
queue_insert(&pq, (uchar *) min_key);
if (pq.elements == 0)
{
/*
Check the only matching row of the only key min_key for NULL matches
in the other columns.
*/
if (test_null_row(min_row_num))
return TRUE;
else
return FALSE;
}
while (TRUE)
{
cur_key= (Ordered_key*) queue_remove(&pq, 0);
cur_row_num= cur_key->current();
if (cur_row_num == min_row_num)
bitmap_set_bit(&matching_keys, cur_key->get_key_idx());
else
{
/* Follows from the correct use of priority queue. */
DBUG_ASSERT(cur_row_num > min_row_num);
if (test_null_row(min_row_num))
return TRUE;
else
{
min_key= cur_key;
min_row_num= cur_row_num;
bitmap_copy(&matching_keys, &null_only_columns);
bitmap_set_bit(&matching_keys, min_key->get_key_idx());
bitmap_union(&matching_keys, &matching_outer_cols);
}
}
if (cur_key->next_same())
queue_insert(&pq, (uchar *) cur_key);
if (pq.elements == 0)
{
/* Check the last row of the last column in PQ for NULL matches. */
if (test_null_row(min_row_num))
return TRUE;
else
return FALSE;
}
}
/* We should never get here. */
DBUG_ASSERT(FALSE);
return FALSE;
}
int subselect_rowid_merge_engine::exec()
{
Item_in_subselect *item_in= (Item_in_subselect *) item;
int res;
/* Try to find a matching row by index lookup. */
res= lookup_engine->copy_ref_key_simple();
if (res == -1)
{
/* The result is FALSE based on the outer reference. */
item_in->value= 0;
item_in->null_value= 0;
return 0;
}
else if (res == 0)
{
if ((res= lookup_engine->index_lookup()))
{
/* An error occured during lookup(). */
item_in->value= 0;
item_in->null_value= 0;
return res;
}
else if (item_in->value)
{
/*
A complete match was found, the result of IN is TRUE.
Notice: (this->item == lookup_engine->item)
*/
return 0;
}
}
if (has_covering_null_row && !keys_count)
{
/*
If there is a NULL-only row that coveres all columns the result of IN
is UNKNOWN.
*/
item_in->value= 0;
/*
TIMOUR: which one is the right way to propagate an UNKNOWN result?
Should we also set empty_result_set= FALSE; ???
*/
//item_in->was_null= 1;
item_in->null_value= 1;
return 0;
}
/* All data accesses during execution are via handler::ha_rnd_pos() */
if (tmp_table->file->inited)
tmp_table->file->ha_index_end();
tmp_table->file->ha_rnd_init(0);
/*
There is no complete match. Look for a partial match (UNKNOWN result), or
no match (FALSE).
*/
if (partial_match())
{
/* The result of IN is UNKNOWN. */
item_in->value= 0;
/*
TIMOUR: which one is the right way to propagate an UNKNOWN result?
Should we also set empty_result_set= FALSE; ???
*/
//item_in->was_null= 1;
item_in->null_value= 1;
}
else
{
/* The result of IN is FALSE. */
item_in->value= 0;
/*
TIMOUR: which one is the right way to propagate an UNKNOWN result?
Should we also set empty_result_set= FALSE; ???
*/
//item_in->was_null= 0;
item_in->null_value= 0;
}
tmp_table->file->ha_rnd_end();
return 0;
}
sql/item_subselect.h
View file @ a292ca34
......@@ -297,7 +297,7 @@ class Item_exists_subselect :public Item_subselect
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 @@ class Item_in_subselect :public Item_exists_subselect
*/
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 @@ class Item_in_subselect :public Item_exists_subselect
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 @@ class Item_in_subselect :public Item_exists_subselect
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 @@ class Item_in_subselect :public Item_exists_subselect
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 @@ class subselect_engine: public Sql_alloc
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 @@ class subselect_uniquesubquery_engine: public subselect_engine
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
}
/*
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 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. 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.
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_uniquesubquery_engine
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_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
};
sql/opt_subselect.cc
View file @ a292ca34
......@@ -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;
}
......
sql/sql_class.cc
View file @ a292ca34
......@@ -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
****************************************************************************/
......
sql/sql_class.h
View file @ a292ca34
......@@ -2740,17 +2740,18 @@ class TMP_TABLE_PARAM :public Sql_alloc
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,
virtual bool create_result_table(THD *thd, List<Item> *column_types,
bool is_distinct, ulonglong options,
const char *alias, bool bit_fields_as_long);
};
......@@ -2776,6 +2777,74 @@ class select_singlerow_subselect :public select_subselect
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
{
......
sql/sql_select.cc
View file @ a292ca34
......@@ -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.
......
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