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mariadb-columnstore-engine/dbcon/mysql/ha_mcs_pushdown.cpp

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/*
Copyright (c) 2019 MariaDB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#include <typeinfo>
#include <string>
// This makes specific MDB classes' attributes public to implement
// MCOL-4740 temporary solution. Search for MCOL-4740
// to get the actual place where it is used.
#define updated_leaves \
updated_leaves; \
\
public:
#include "ha_mcs_pushdown.h"
void update_counters_on_multi_update()
{
if (ha_mcs_common::isMultiUpdateStatement(current_thd->lex->sql_command) &&
!ha_mcs_common::isForeignTableUpdate(current_thd))
{
SELECT_LEX_UNIT* unit = &current_thd->lex->unit;
SELECT_LEX* select_lex = unit->first_select();
auto* multi = (select_lex->join) ? reinterpret_cast<multi_update*>(select_lex->join->result) : nullptr;
if (multi)
{
multi->table_to_update = multi->update_tables ? multi->update_tables->table : 0;
cal_impl_if::cal_connection_info* ci =
reinterpret_cast<cal_impl_if::cal_connection_info*>(get_fe_conn_info_ptr());
if (ci)
{
multi->updated = multi->found = ci->affectedRows;
}
}
}
}
void check_walk(const Item* item, void* arg);
void restore_query_state(ha_columnstore_select_handler* handler)
{
for (auto iter = handler->tableOuterJoinMap.begin(); iter != handler->tableOuterJoinMap.end(); iter++)
{
iter->first->outer_join = iter->second;
}
}
void mutate_optimizer_flags(THD* thd_)
{
// MCOL-2178 Disable all optimizer flags as it was in the fork.
// CS restores it later in SH::scan_end() and in case of an error
// in SH::scan_init()
ulonglong flags_to_set = OPTIMIZER_SWITCH_MATERIALIZATION | OPTIMIZER_SWITCH_COND_PUSHDOWN_FOR_DERIVED |
OPTIMIZER_SWITCH_COND_PUSHDOWN_FROM_HAVING;
if (thd_->variables.optimizer_switch == flags_to_set)
return;
set_original_optimizer_flags(thd_->variables.optimizer_switch, thd_);
thd_->variables.optimizer_switch = flags_to_set;
}
void restore_optimizer_flags(THD* thd_)
{
// MCOL-2178 restore original optimizer flags after SH, DH
ulonglong orig_flags = get_original_optimizer_flags(thd_);
if (orig_flags)
{
thd_->variables.optimizer_switch = orig_flags;
set_original_optimizer_flags(0, thd_);
}
}
/*@brief find_tables - This traverses Item */
/**********************************************************
* DESCRIPTION:
* This f() pushes TABLE of an Item_field to a list
* provided. The list is used for JOIN predicate check in
* is_joinkeys_predicate().
* PARAMETERS:
* Item * Item to check
* RETURN:
***********************************************************/
void find_tables(const Item* item, void* arg)
{
if (typeid(*item) == typeid(Item_field))
{
Item_field* ifp = (Item_field*)item;
List<TABLE>* tables_list = (List<TABLE>*)arg;
tables_list->push_back(ifp->field->table);
}
}
/*@brief is_joinkeys_predicate - This traverses Item_func*/
/***********************************************************
* DESCRIPTION:
* This f() walks Item_func and checks whether it contains
* JOIN predicate
* PARAMETERS:
* Item_func * Item to walk
* RETURN:
* BOOL false if Item_func isn't a JOIN predicate
* BOOL true otherwise
***********************************************************/
bool is_joinkeys_predicate(const Item_func* ifp)
{
bool result = false;
if (ifp->argument_count() == 2)
{
if (ifp->arguments()[0]->type() == Item::FIELD_ITEM && ifp->arguments()[1]->type() == Item::FIELD_ITEM)
{
Item_field* left = reinterpret_cast<Item_field*>(ifp->arguments()[0]);
Item_field* right = reinterpret_cast<Item_field*>(ifp->arguments()[1]);
// If MDB crashes here with non-fixed Item_field and field == NULL
// there must be a check over on_expr for a different SELECT_LEX.
// e.g. checking subquery with ON from upper query.
if (left->field->table != right->field->table)
{
result = true;
}
}
else
{
List<TABLE> llt;
List<TABLE> rlt;
Item* left = ifp->arguments()[0];
Item* right = ifp->arguments()[1];
// Search for tables inside left and right expressions
// and compare them
left->traverse_cond(find_tables, (void*)&llt, Item::POSTFIX);
right->traverse_cond(find_tables, (void*)&rlt, Item::POSTFIX);
// TODO Find the way to have more then one element or prove
// the idea is useless.
if (llt.elements && rlt.elements && (llt.elem(0) != rlt.elem(0)))
{
result = true;
}
}
}
return result;
}
/*@brief find_nonequi_join - This traverses Item */
/************************************************************
* DESCRIPTION:
* This f() walks Item and looks for a non-equi join
* predicates
* PARAMETERS:
* Item * Item to walk
* RETURN:
***********************************************************/
void find_nonequi_join(const Item* item, void* arg)
{
bool* unsupported_feature = reinterpret_cast<bool*>(arg);
if (*unsupported_feature)
return;
if (item->type() == Item::FUNC_ITEM)
{
const Item_func* ifp = reinterpret_cast<const Item_func*>(item);
// TODO Check for IN
// NOT IN + correlated subquery
if (ifp->functype() != Item_func::EQ_FUNC)
{
if (is_joinkeys_predicate(ifp))
*unsupported_feature = true;
else if (ifp->functype() == Item_func::NOT_FUNC && ifp->arguments()[0]->type() == Item::EXPR_CACHE_ITEM)
{
check_walk(ifp->arguments()[0], arg);
}
}
}
}
/*@brief find_join - This traverses Item */
/************************************************************
* DESCRIPTION:
* This f() walks traverses Item looking for JOIN, SEMI-JOIN
* predicates.
* PARAMETERS:
* Item * Item to traverse
* RETURN:
***********************************************************/
void find_join(const Item* item, void* arg)
{
bool* unsupported_feature = reinterpret_cast<bool*>(arg);
if (*unsupported_feature)
return;
if (item->type() == Item::FUNC_ITEM)
{
const Item_func* ifp = reinterpret_cast<const Item_func*>(item);
// TODO Check for IN
// NOT IN + correlated subquery
{
if (is_joinkeys_predicate(ifp))
*unsupported_feature = true;
else if (ifp->functype() == Item_func::NOT_FUNC && ifp->arguments()[0]->type() == Item::EXPR_CACHE_ITEM)
{
check_walk(ifp->arguments()[0], arg);
}
}
}
}
/*@brief save_join_predicate - This traverses Item */
/************************************************************
* DESCRIPTION:
* This f() walks Item and saves found JOIN predicates into
* a List. The list will be used for a simple CROSS JOIN
* check in create_DH.
* PARAMETERS:
* Item * Item to walk
* RETURN:
***********************************************************/
void save_join_predicates(const Item* item, void* arg)
{
if (item->type() == Item::FUNC_ITEM)
{
const Item_func* ifp = reinterpret_cast<const Item_func*>(item);
if (is_joinkeys_predicate(ifp))
{
List<Item>* join_preds_list = (List<Item>*)arg;
join_preds_list->push_back(const_cast<Item*>(item));
}
}
}
/*@brief check_walk - It traverses filter conditions */
/************************************************************
* DESCRIPTION:
* It traverses filter predicates looking for unsupported
* JOIN types: non-equi JOIN, e.g t1.c1 > t2.c2;
* logical OR.
* PARAMETERS:
* thd - THD pointer.
* derived - TABLE_LIST* to work with.
* RETURN:
***********************************************************/
void check_walk(const Item* item, void* arg)
{
bool* unsupported_feature = reinterpret_cast<bool*>(arg);
if (*unsupported_feature)
return;
switch (item->type())
{
case Item::FUNC_ITEM:
{
find_nonequi_join(item, arg);
break;
}
case Item::EXPR_CACHE_ITEM: // IN + correlated subquery
{
const Item_cache_wrapper* icw = reinterpret_cast<const Item_cache_wrapper*>(item);
if (icw->get_orig_item()->type() == Item::FUNC_ITEM)
{
const Item_func* ifp = reinterpret_cast<const Item_func*>(icw->get_orig_item());
if (ifp->argument_count() == 2 && (ifp->arguments()[0]->type() == Item::Item::SUBSELECT_ITEM ||
ifp->arguments()[1]->type() == Item::Item::SUBSELECT_ITEM))
{
*unsupported_feature = true;
return;
}
}
break;
}
case Item::COND_ITEM: // OR contains JOIN conds thats is unsupported yet
{
Item_cond* icp = (Item_cond*)item;
if (is_cond_or(icp))
{
bool left_flag = false, right_flag = false;
if (icp->argument_list()->elements >= 2)
{
Item* left;
Item* right;
List_iterator<Item> li(*icp->argument_list());
left = li++;
right = li++;
left->traverse_cond(find_join, (void*)&left_flag, Item::POSTFIX);
right->traverse_cond(find_join, (void*)&right_flag, Item::POSTFIX);
if (left_flag && right_flag)
{
*unsupported_feature = true;
}
}
}
break;
}
default:
{
break;
}
}
}
/*@brief check_user_var_func - This traverses Item */
/************************************************************
* DESCRIPTION:
* This f() walks Item looking for the existence of
* "set_user_var" or "get_user_var" functions.
* PARAMETERS:
* Item * Item to traverse
* RETURN:
***********************************************************/
void check_user_var_func(const Item* item, void* arg)
{
bool* unsupported_feature = reinterpret_cast<bool*>(arg);
if (*unsupported_feature)
return;
if (item->type() == Item::FUNC_ITEM)
{
const Item_func* ifp = reinterpret_cast<const Item_func*>(item);
std::string funcname = ifp->func_name();
if (funcname == "set_user_var")
{
*unsupported_feature = true;
}
}
}
void item_check(Item* item, bool* unsupported_feature)
{
switch (item->type())
{
case Item::COND_ITEM:
{
item->traverse_cond(check_user_var_func, unsupported_feature, Item::POSTFIX);
break;
}
case Item::FUNC_ITEM:
{
item->traverse_cond(check_user_var_func, unsupported_feature, Item::POSTFIX);
break;
}
default:
{
item->traverse_cond(check_user_var_func, unsupported_feature, Item::POSTFIX);
break;
}
}
}
bool check_user_var(SELECT_LEX* select_lex)
{
List_iterator_fast<Item> it(select_lex->item_list);
Item* item;
bool is_user_var_func = false;
while ((item = it++))
{
item_check(item, &is_user_var_func);
if (is_user_var_func)
{
return true;
}
}
JOIN* join = select_lex->join;
if (join->conds)
{
join->conds->traverse_cond(check_user_var_func, &is_user_var_func, Item::POSTFIX);
}
return is_user_var_func;
}
/*@brief create_columnstore_group_by_handler- Creates handler*/
/***********************************************************
* DESCRIPTION:
* Creates a group_by pushdown handler if there is no:
* non-equi JOIN, e.g * t1.c1 > t2.c2
* logical OR in the filter predicates
* Impossible WHERE
* Impossible HAVING
* and there is either GROUP BY or aggregation function
* exists at the top level.
* Valid queries with the last two crashes the server if
* processed.
* Details are in server/sql/group_by_handler.h
* PARAMETERS:
* thd - THD pointer
* query - Query structure LFM in group_by_handler.h
* RETURN:
* group_by_handler if success
* NULL in other case
***********************************************************/
group_by_handler* create_columnstore_group_by_handler(THD* thd, Query* query)
{
ha_mcs_group_by_handler* handler = NULL;
// Disable GBH.
return handler;
// same as thd->lex->current_select
SELECT_LEX* select_lex = query->from->select_lex;
// MCOL-2178 Disable SP support in the group_by_handler for now
// Check the session variable value to enable/disable use of
// group_by_handler. There is no GBH if SH works for the query.
if ((get_select_handler_mode(thd) == mcs_select_handler_mode_t::ON) || !get_group_by_handler(thd) ||
(thd->lex)->sphead)
{
return handler;
}
// Create a handler if query is valid. See comments for details.
if (query->group_by || select_lex->with_sum_func)
{
bool unsupported_feature = false;
// revisit SELECT_LEX for all units
for (TABLE_LIST* tl = query->from; !unsupported_feature && tl; tl = tl->next_global)
{
select_lex = tl->select_lex;
// Correlation subquery. Comming soon so fail on this yet.
unsupported_feature = select_lex->is_correlated;
// Impossible HAVING or WHERE
if (!unsupported_feature &&
(select_lex->having_value == Item::COND_FALSE || select_lex->cond_value == Item::COND_FALSE))
{
unsupported_feature = true;
}
// Unsupported JOIN conditions
if (!unsupported_feature)
{
JOIN* join = select_lex->join;
if (unsupported_feature == false && join && join->conds)
{
join->conds->traverse_cond(check_walk, &unsupported_feature, Item::POSTFIX);
}
if (unsupported_feature == false && select_lex->where)
{
select_lex->where->traverse_cond(check_walk, &unsupported_feature, Item::POSTFIX);
}
}
// Iterate and traverse through the item list and the JOIN cond
// and do not create GBH if the unsupported (set_user_var)
// function is present.
if (check_user_var(select_lex))
{
return handler;
}
} // unsupported features check ends here
if (!unsupported_feature)
{
handler = new ha_mcs_group_by_handler(thd, query);
// Notify the server, that CS handles GROUP BY, ORDER BY and HAVING clauses.
query->group_by = NULL;
query->order_by = NULL;
query->having = NULL;
}
}
return handler;
}
/*@brief create_columnstore_derived_handler- Creates handler*/
/************************************************************
* DESCRIPTION:
* Creates a derived handler if there is no non-equi JOIN, e.g
* t1.c1 > t2.c2 and logical OR in the filter predicates.
* More details in server/sql/derived_handler.h
* PARAMETERS:
* thd - THD pointer.
* derived - TABLE_LIST* to work with.
* RETURN:
* derived_handler if possible
* NULL in other case
***********************************************************/
derived_handler* create_columnstore_derived_handler(THD* thd, TABLE_LIST* table_ptr)
{
ha_columnstore_derived_handler* handler = NULL;
// MCOL-2178 Disable SP support in the derived_handler for now
// Check the session variable value to enable/disable use of
// derived_handler
if (!get_derived_handler(thd) || (thd->lex)->sphead)
{
return handler;
}
// Disable derived handler for prepared statements
if (thd->stmt_arena && thd->stmt_arena->is_stmt_execute())
return handler;
// MCOL-1482 Disable derived_handler if the multi-table update
// statement contains a non-columnstore table.
if (ha_mcs_common::isUpdateHasForeignTable(thd))
{
return handler;
}
SELECT_LEX_UNIT* unit = table_ptr->derived;
SELECT_LEX* sl = unit->first_select();
bool unsupported_feature = false;
// Impossible HAVING or WHERE
if (unsupported_feature || sl->having_value == Item::COND_FALSE || sl->cond_value == Item::COND_FALSE)
{
unsupported_feature = true;
}
// JOIN expression from WHERE, ON expressions
JOIN* join = sl->join;
// TODO DRRTUY Make a proper tree traverse
// To search for CROSS JOIN-s we use tree invariant
// G(V,E) where [V] = [E]+1
List<Item> join_preds_list;
TABLE_LIST* tl;
for (tl = sl->get_table_list(); !unsupported_feature && tl; tl = tl->next_local)
{
if (tl->where)
{
tl->where->traverse_cond(check_walk, &unsupported_feature, Item::POSTFIX);
tl->where->traverse_cond(save_join_predicates, &join_preds_list, Item::POSTFIX);
}
// Looking for JOIN with ON expression through
// TABLE_LIST in FROM until CS meets unsupported feature
if (tl->on_expr)
{
tl->on_expr->traverse_cond(check_walk, &unsupported_feature, Item::POSTFIX);
tl->on_expr->traverse_cond(save_join_predicates, &join_preds_list, Item::POSTFIX);
}
// Iterate and traverse through the item list and the JOIN cond
// and do not create DH if the unsupported (set_user_var)
// function is present.
if (check_user_var(tl->select_lex))
{
return handler;
}
}
if (!unsupported_feature && !join_preds_list.elements && join && join->conds)
{
join->conds->traverse_cond(check_walk, &unsupported_feature, Item::POSTFIX);
join->conds->traverse_cond(save_join_predicates, &join_preds_list, Item::POSTFIX);
}
// CROSS JOIN w/o conditions isn't supported until MCOL-301
// is ready.
if (!unsupported_feature && join && join->table_count >= 2 && !join_preds_list.elements)
{
unsupported_feature = true;
}
// CROSS JOIN with not enough JOIN predicates
if (!unsupported_feature && join && join_preds_list.elements < join->table_count - 1)
{
unsupported_feature = true;
}
if (!unsupported_feature)
handler = new ha_columnstore_derived_handler(thd, table_ptr);
return handler;
}
/***********************************************************
* DESCRIPTION:
* derived_handler constructor
* PARAMETERS:
* thd - THD pointer.
* tbl - tables involved.
***********************************************************/
ha_columnstore_derived_handler::ha_columnstore_derived_handler(THD* thd, TABLE_LIST* dt)
: derived_handler(thd, mcs_hton)
{
derived = dt;
const char* timeZone = thd->variables.time_zone->get_name()->ptr();
dataconvert::timeZoneToOffset(timeZone, strlen(timeZone), &time_zone);
}
/***********************************************************
* DESCRIPTION:
* derived_handler destructor
***********************************************************/
ha_columnstore_derived_handler::~ha_columnstore_derived_handler()
{
}
/*@brief Initiate the query for derived_handler */
/***********************************************************
* DESCRIPTION:
* Execute the query and saves derived table query.
* PARAMETERS:
*
* RETURN:
* rc as int
***********************************************************/
int ha_columnstore_derived_handler::init_scan()
{
DBUG_ENTER("ha_columnstore_derived_handler::init_scan");
mcs_handler_info mhi(reinterpret_cast<void*>(this), DERIVED);
// this::table is the place for the result set
int rc = ha_mcs_impl_pushdown_init(&mhi, table);
DBUG_RETURN(rc);
}
/*@brief Fetch next row for derived_handler */
/***********************************************************
* DESCRIPTION:
* Fetches next row and saves it in the temp table
* PARAMETERS:
*
* RETURN:
* rc as int
*
***********************************************************/
int ha_columnstore_derived_handler::next_row()
{
DBUG_ENTER("ha_columnstore_derived_handler::next_row");
int rc = ha_mcs_impl_rnd_next(table->record[0], table, time_zone);
DBUG_RETURN(rc);
}
/*@brief Finishes the scan and clean it up */
/***********************************************************
* DESCRIPTION:
* Finishes the scan for derived handler
* PARAMETERS:
*
* RETURN:
* rc as int
*
***********************************************************/
int ha_columnstore_derived_handler::end_scan()
{
DBUG_ENTER("ha_columnstore_derived_handler::end_scan");
int rc = ha_mcs_impl_rnd_end(table, true);
DBUG_RETURN(rc);
}
void ha_columnstore_derived_handler::print_error(int, unsigned long)
{
}
/***********************************************************
* DESCRIPTION:
* GROUP BY handler constructor
* PARAMETERS:
* thd - THD pointer.
* query - Query describing structure
***********************************************************/
ha_mcs_group_by_handler::ha_mcs_group_by_handler(THD* thd_arg, Query* query)
: group_by_handler(thd_arg, mcs_hton)
, select(query->select)
, table_list(query->from)
, distinct(query->distinct)
, where(query->where)
, group_by(query->group_by)
, order_by(query->order_by)
, having(query->having)
{
const char* timeZone = thd_arg->variables.time_zone->get_name()->ptr();
dataconvert::timeZoneToOffset(timeZone, strlen(timeZone), &time_zone);
}
/***********************************************************
* DESCRIPTION:
* GROUP BY destructor
***********************************************************/
ha_mcs_group_by_handler::~ha_mcs_group_by_handler()
{
}
/***********************************************************
* DESCRIPTION:
* Makes the plan and prepares the data
* RETURN:
* int rc
***********************************************************/
int ha_mcs_group_by_handler::init_scan()
{
DBUG_ENTER("ha_mcs_group_by_handler::init_scan");
mcs_handler_info mhi = mcs_handler_info(reinterpret_cast<void*>(this), GROUP_BY);
int rc = ha_mcs_impl_group_by_init(&mhi, table);
DBUG_RETURN(rc);
}
/***********************************************************
* DESCRIPTION:
* Fetches a row and saves it to a temporary table.
* RETURN:
* int rc
***********************************************************/
int ha_mcs_group_by_handler::next_row()
{
DBUG_ENTER("ha_mcs_group_by_handler::next_row");
int rc = ha_mcs_impl_group_by_next(table, time_zone);
DBUG_RETURN(rc);
}
/***********************************************************
* DESCRIPTION:
* Shuts the scan down.
* RETURN:
* int rc
***********************************************************/
int ha_mcs_group_by_handler::end_scan()
{
DBUG_ENTER("ha_mcs_group_by_handler::end_scan");
int rc = ha_mcs_impl_group_by_end(table);
DBUG_RETURN(rc);
}
/*@brief create_columnstore_select_handler_- Creates handler
************************************************************
* DESCRIPTION:
* Creates a select handler if there is no non-equi JOIN, e.g
* t1.c1 > t2.c2 and logical OR in the filter predicates.
* More details in server/sql/select_handler.h
* PARAMETERS:
* thd - THD pointer.
* sel_lex - SELECT_LEX* that describes the query.
* sel_unit - SELECT_LEX_UNIT* that describes the query.
* RETURN:
* select_handler if possible
* NULL in other case
***********************************************************/
select_handler* create_columnstore_select_handler_(THD* thd, SELECT_LEX* sel_lex, SELECT_LEX_UNIT* sel_unit)
{
mcs_select_handler_mode_t select_handler_mode = get_select_handler_mode(thd);
// Check the session variable value to enable/disable use of
// select_handler
if ((select_handler_mode == mcs_select_handler_mode_t::OFF) ||
((thd->lex)->sphead && !get_select_handler_in_stored_procedures(thd)))
{
return nullptr;
}
// MCOL-1482 Disable select_handler for a multi-table update
// with a non-columnstore table as the target table of the update
// operation.
if (ha_mcs_common::isForeignTableUpdate(thd))
{
return nullptr;
}
// Flag to indicate if this is a prepared statement
bool isPS = thd->stmt_arena && thd->stmt_arena->is_stmt_execute();
// Disable processing of select_result_interceptor classes
// which intercept and transform result set rows. E.g.:
// select a,b into @a1, @a2 from t1;
select_dumpvar* dumpvar = dynamic_cast<select_dumpvar*>((thd->lex)->result);
if (dumpvar && !dumpvar->var_list.is_empty() && !isPS)
{
return nullptr;
}
// Select_handler couldn't properly process UPSERT..SELECT
if ((thd->lex)->sql_command == SQLCOM_INSERT_SELECT && thd->lex->duplicates == DUP_UPDATE)
{
return nullptr;
}
// MCOL-5432 Disable partial pushdown of the UNION operation if the query
// involves an order by or a limit clause.
if (sel_lex && sel_unit &&
(sel_unit->global_parameters()->limit_params.explicit_limit == true ||
sel_unit->global_parameters()->order_list.elements != 0))
{
return nullptr;
}
std::vector<SELECT_LEX*> select_lex_vec;
if (sel_unit && !sel_lex)
{
for (SELECT_LEX* sl = sel_unit->first_select(); sl; sl = sl->next_select())
{
select_lex_vec.push_back(sl);
}
}
else
{
select_lex_vec.push_back(sel_lex);
}
for (size_t i = 0; i < select_lex_vec.size(); i++)
{
SELECT_LEX* select_lex = select_lex_vec[i];
// Iterate and traverse through the item list and the JOIN cond
// and do not create SH if the unsupported (set_user_var)
// function is present.
TABLE_LIST* table_ptr = select_lex->get_table_list();
for (; table_ptr; table_ptr = table_ptr->next_global)
{
if (check_user_var(table_ptr->select_lex))
{
return nullptr;
}
}
}
// We apply dedicated rewrites from MDB here so MDB's data structures
// becomes dirty and CS has to raise an error in case of any problem
// or unsupported feature.
ha_columnstore_select_handler* handler;
if (sel_unit && sel_lex) // partial pushdown of the SELECT_LEX_UNIT
{
handler = new ha_columnstore_select_handler(thd, sel_lex, sel_unit);
}
else if (sel_unit) // complete pushdown of the SELECT_LEX_UNIT
{
handler = new ha_columnstore_select_handler(thd, sel_unit);
}
else // Query only has a SELECT_LEX, no SELECT_LEX_UNIT
{
handler = new ha_columnstore_select_handler(thd, sel_lex);
}
for (size_t i = 0; i < select_lex_vec.size(); i++)
{
SELECT_LEX* select_lex = select_lex_vec[i];
JOIN* join = select_lex->join;
if (select_lex->first_cond_optimization && select_lex->handle_derived(thd->lex, DT_MERGE))
{
if (!thd->is_error())
{
my_printf_error(ER_INTERNAL_ERROR, "%s", MYF(0), "Error occurred in select_lex::handle_derived()");
}
return handler;
}
// This is partially taken from JOIN::optimize_inner() in sql/sql_select.cc
if (select_lex->first_cond_optimization)
{
create_explain_query_if_not_exists(thd->lex, thd->mem_root);
Query_arena *arena, backup;
arena = thd->activate_stmt_arena_if_needed(&backup);
COND* conds = join->conds;
select_lex->where = conds;
if (isPS)
{
select_lex->prep_where = conds ? conds->copy_andor_structure(thd) : 0;
}
select_lex->update_used_tables();
if (arena)
thd->restore_active_arena(arena, &backup);
#ifdef DEBUG_WALK_COND
if (conds)
{
conds->traverse_cond(cal_impl_if::debug_walk, NULL, Item::POSTFIX);
}
#endif
}
}
// Attempt to execute the query using the select handler.
// If query execution fails and columnstore_select_handler=AUTO,
// fallback to table mode.
// Skip execution for EXPLAIN queries
if (!thd->lex->describe)
{
for (size_t i = 0; i < select_lex_vec.size(); i++)
{
SELECT_LEX* select_lex = select_lex_vec[i];
JOIN* join = select_lex->join;
// This is taken from JOIN::optimize()
join->fields = &select_lex->item_list;
// Instantiate handler::table, which is the place for the result set.
if ((i == 0) && handler->prepare())
{
// check fallback
if (select_handler_mode == mcs_select_handler_mode_t::AUTO) // columnstore_select_handler=AUTO
{
push_warning(thd, Sql_condition::WARN_LEVEL_WARN, 9999,
"MCS select_handler execution failed. Falling back to server execution");
restore_query_state(handler);
delete handler;
return nullptr;
}
// error out
if (!thd->is_error())
{
my_printf_error(ER_INTERNAL_ERROR, "%s", MYF(0), "Error occurred in handler->prepare()");
}
return handler;
}
// Prepare query execution
// This is taken from JOIN::exec_inner()
if (!select_lex->outer_select() && // (1)
select_lex != select_lex->master_unit()->fake_select_lex) // (2)
thd->lex->set_limit_rows_examined();
if ((!sel_unit || sel_lex) && !join->tables_list && (join->table_count || !select_lex->with_sum_func) &&
!select_lex->have_window_funcs())
{
if (!thd->is_error())
{
restore_query_state(handler);
delete handler;
return nullptr;
}
return handler;
}
if (!join->zero_result_cause && join->exec_const_cond && !join->exec_const_cond->val_int())
join->zero_result_cause = "Impossible WHERE noticed after reading const tables";
// We've called exec_const_cond->val_int(). This may have caused an error.
if (unlikely(thd->is_error()))
{
// error out
handler->pushdown_init_rc = 1;
return handler;
}
if (join->zero_result_cause)
{
if (join->select_lex->have_window_funcs() && join->send_row_on_empty_set())
{
join->const_tables = join->table_count;
join->first_select = sub_select_postjoin_aggr;
}
else
{
if (!thd->is_error())
{
restore_query_state(handler);
delete handler;
return nullptr;
}
return handler;
}
}
if ((join->select_lex->options & OPTION_SCHEMA_TABLE) &&
get_schema_tables_result(join, PROCESSED_BY_JOIN_EXEC))
{
if (!thd->is_error())
{
my_printf_error(ER_INTERNAL_ERROR, "%s", MYF(0), "Error occurred in get_schema_tables_result()");
}
return handler;
}
}
handler->scan_initialized = true;
mcs_handler_info mhi(reinterpret_cast<void*>(handler), SELECT);
bool isSelectLexUnit = (sel_unit && !sel_lex) ? true : false;
if ((handler->pushdown_init_rc = ha_mcs_impl_pushdown_init(&mhi, handler->table, isSelectLexUnit)))
{
// check fallback
if (select_handler_mode == mcs_select_handler_mode_t::AUTO)
{
restore_query_state(handler);
std::ostringstream oss;
oss << "MCS select_handler execution failed";
if (thd->is_error())
{
oss << " due to: ";
oss << thd->get_stmt_da()->sql_errno() << ": ";
oss << thd->get_stmt_da()->message();
oss << " F";
thd->clear_error();
}
else
{
oss << ", f";
}
oss << "alling back to server execution";
thd->get_stmt_da()->clear_warning_info(thd->query_id);
push_warning(thd, Sql_condition::WARN_LEVEL_WARN, 9999, oss.str().c_str());
delete handler;
return nullptr;
}
if (!thd->is_error())
{
my_printf_error(ER_INTERNAL_ERROR, "%s", MYF(0), "Error occurred in ha_mcs_impl_pushdown_init()");
}
// We had an error in `ha_mcs_impl_pushdown_init`, no need to continue execution of this query.
return handler;
}
for (size_t i = 0; i < select_lex_vec.size(); i++)
{
SELECT_LEX* select_lex = select_lex_vec[i];
// Unset select_lex::first_cond_optimization
if (select_lex->first_cond_optimization)
{
first_cond_optimization_flag_toggle(select_lex, &first_cond_optimization_flag_unset);
}
}
}
return handler;
}
select_handler* create_columnstore_select_handler(THD* thd, SELECT_LEX* select_lex, SELECT_LEX_UNIT* sel_unit)
{
return create_columnstore_select_handler_(thd, select_lex, sel_unit);
}
select_handler* create_columnstore_unit_handler(THD* thd, SELECT_LEX_UNIT* sel_unit)
{
if (thd->lex->sql_command == SQLCOM_CREATE_VIEW)
{
return nullptr;
}
if (thd->stmt_arena && thd->stmt_arena->is_stmt_prepare())
{
return nullptr;
}
// MCOL-5432 Disable UNION pushdown if the query involves an order by
// or a limit clause.
if (sel_unit->global_parameters()->limit_params.explicit_limit == true ||
sel_unit->global_parameters()->order_list.elements != 0)
{
return nullptr;
}
return create_columnstore_select_handler_(thd, 0, sel_unit);
}
/***********************************************************
* DESCRIPTION:
* select_handler constructor
* PARAMETERS:
* thd - THD pointer.
* sel_lex - semantic tree for the query.
***********************************************************/
ha_columnstore_select_handler::ha_columnstore_select_handler(THD* thd, SELECT_LEX* sel_lex)
: select_handler(thd, mcs_hton, sel_lex)
, prepared(false)
, scan_ended(false)
, scan_initialized(false)
, pushdown_init_rc(0)
{
const char* timeZone = thd->variables.time_zone->get_name()->ptr();
dataconvert::timeZoneToOffset(timeZone, strlen(timeZone), &time_zone);
}
/***********************************************************
* DESCRIPTION:
* select_handler constructor
* PARAMETERS:
* thd - THD pointer.
* sel_unit - semantic tree for the query.
***********************************************************/
ha_columnstore_select_handler::ha_columnstore_select_handler(THD* thd, SELECT_LEX_UNIT* sel_unit)
: select_handler(thd, mcs_hton, sel_unit)
, prepared(false)
, scan_ended(false)
, scan_initialized(false)
, pushdown_init_rc(0)
{
const char* timeZone = thd->variables.time_zone->get_name()->ptr();
dataconvert::timeZoneToOffset(timeZone, strlen(timeZone), &time_zone);
}
/***********************************************************
* DESCRIPTION:
* select_handler constructor
* PARAMETERS:
* thd - THD pointer.
* sel_lex - semantic tree for the query.
* sel_unit - unit containing SELECT_LEX's
***********************************************************/
ha_columnstore_select_handler::ha_columnstore_select_handler(THD* thd, SELECT_LEX* sel_lex,
SELECT_LEX_UNIT* sel_unit)
: select_handler(thd, mcs_hton, sel_lex, sel_unit)
, prepared(false)
, scan_ended(false)
, scan_initialized(false)
, pushdown_init_rc(0)
{
const char* timeZone = thd->variables.time_zone->get_name()->ptr();
dataconvert::timeZoneToOffset(timeZone, strlen(timeZone), &time_zone);
}
/***********************************************************
* DESCRIPTION:
* select_handler constructor
***********************************************************/
ha_columnstore_select_handler::~ha_columnstore_select_handler()
{
if (scan_initialized && !scan_ended)
{
end_scan();
}
}
/*@brief Initiate the query for select_handler */
/***********************************************************
* DESCRIPTION:
* Execute the query and saves select table query.
* PARAMETERS:
*
* RETURN:
* rc as int
***********************************************************/
int ha_columnstore_select_handler::init_scan()
{
DBUG_ENTER("ha_columnstore_select_handler::init_scan");
DBUG_RETURN(pushdown_init_rc);
}
/*@brief Fetch next row for select_handler */
/***********************************************************
* DESCRIPTION:
* Fetches next row and saves it in the temp table
* PARAMETERS:
*
* RETURN:
* rc as int
*
***********************************************************/
int ha_columnstore_select_handler::next_row()
{
DBUG_ENTER("ha_columnstore_select_handler::next_row");
int rc = ha_mcs_impl_select_next(table->record[0], table, time_zone);
DBUG_RETURN(rc);
}
/*@brief Finishes the scan and clean it up */
/***********************************************************
* DESCRIPTION:
* Finishes the scan for select handler
* PARAMETERS:
*
* RETURN:
* rc as int
*
***********************************************************/
int ha_columnstore_select_handler::end_scan()
{
DBUG_ENTER("ha_columnstore_select_handler::end_scan");
scan_ended = true;
// MCOL-4740 multi_update::send_eof(), which outputs the affected
// number of rows to the client, is called after handler::rnd_end().
// So we set multi_update::updated and multi_update::found here.
update_counters_on_multi_update();
int rc = ha_mcs_impl_rnd_end(table, true);
DBUG_RETURN(rc);
}
// Copy of select_handler::prepare (see sql/select_handler.cc),
// with an added if guard
bool ha_columnstore_select_handler::prepare()
{
DBUG_ENTER("ha_columnstore_select_handler::prepare");
if (prepared)
DBUG_RETURN(pushdown_init_rc ? true : false);
prepared = true;
if ((!table && !(table = create_tmp_table(thd))) || table->fill_item_list(&result_columns))
{
pushdown_init_rc = 1;
DBUG_RETURN(true);
}
DBUG_RETURN(false);
}
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