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Merge pull request #852 from tntnatbry/fix-exists-limit-subselectitem-orderby

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Enable Item::SUBSELECT_ITEM in the order by clause and Do not set the limit to 1 for "exists" in a subquery.
This commit is contained in:
Roman Nozdrin
2019-09-05 04:12:59 -07:00
committed by GitHub
parent dd7bd6fe4a 67738303ba
commit 64ceb8686f
2 changed files with 25 additions and 6 deletions
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11
dbcon/joblist/jlf_subquery.cpp
View File

@@ -809,6 +809,17 @@ void addOrderByAndLimit(CalpontSelectExecutionPlan* csep, JobInfo& jobInfo)
if (sc->colPosition() == -1)
{
sc = dynamic_cast<SimpleColumn*>(jobInfo.deliveredCols[sc->orderPos()].get());
// TODO Investigate why this could be NULL
if (sc == NULL)
{
const ReturnedColumn* rc = dynamic_cast<const ReturnedColumn*>(orderByCols[i].get());
uint64_t eid = rc->expressionId();
CalpontSystemCatalog::ColType ct = rc->resultType();
tupleKey = getExpTupleKey(jobInfo, eid);
jobInfo.orderByColVec.push_back(make_pair(tupleKey, orderByCols[i]->asc()));
continue;
}
}
else
{

20
dbcon/mysql/ha_calpont_execplan.cpp
View File

@@ -7723,9 +7723,6 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex,
}
else if (ord_item->type() == Item::SUBSELECT_ITEM)
{
string emsg = IDBErrorInfo::instance()->errorMsg(ERR_NON_SUPPORT_ORDER_BY);
setError(gwi.thd, ER_CHECK_NOT_IMPLEMENTED, emsg, gwi);
return ER_CHECK_NOT_IMPLEMENTED;
}
else
{
@@ -7766,7 +7763,20 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex,
// non-MAIN union branch
if (unionSel || gwi.subSelectType != CalpontSelectExecutionPlan::MAIN_SELECT)
{
if (select_lex.master_unit()->global_parameters()->explicit_limit)
/* Consider the following query:
"select a from t1 where exists (select b from t2 where a=b);"
CS first builds a hash table for t2, then pushes down the hash to
PrimProc for a distributed hash join execution, with t1 being the
large-side table. However, the server applies an optimization in
Item_exists_subselect::fix_length_and_dec in sql/item_subselect.cc
(see server commit ae476868a5394041a00e75a29c7d45917e8dfae8)
where it sets explicit_limit to true, which causes csep->limitNum set to 1.
This causes the hash table for t2 to only contain a single record for the
hash join, giving less number of rows in the output result set than expected.
We therefore do not allow limit set to 1 here for such queries.
*/
if (gwi.subSelectType != CalpontSelectExecutionPlan::IN_SUBS &&
select_lex.master_unit()->global_parameters()->explicit_limit)
{
if (select_lex.master_unit()->global_parameters()->offset_limit)
{
@@ -7779,7 +7789,6 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex,
Item_int* select = (Item_int*)select_lex.master_unit()->global_parameters()->select_limit;
csep->limitNum(select->val_int());
}
}
}
// union with explicit select at the top level
@@ -7815,7 +7824,6 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex,
limitOffset = join->select_lex->offset_limit->val_int();
limitNum = join->select_lex->select_limit->val_int();
}
else if (join->unit)
{
limitOffset = join->unit->offset_limit_cnt;