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Merge pull request #1828 from tntnatbry/MCOL-4543-4589

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MCOL -4543/MCOL-4589 Subquery optimization
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Roman Nozdrin
2021-04-14 13:50:46 +03:00
committed by GitHub
parent 20ac239a3e dfa9657f2e
commit f4b02a7aca
5 changed files with 446 additions and 16 deletions
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39
dbcon/mysql/ha_mcs_execplan.cpp
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@ -2920,15 +2920,46 @@ SimpleColumn* getSmallestColumn(boost::shared_ptr<CalpontSystemCatalog> csc,
if (tan.alias == csep->derivedTbAlias())
{
assert (!csep->returnedCols().empty());
ReturnedColumn* rc = dynamic_cast<ReturnedColumn*>(csep->returnedCols()[0].get());
const CalpontSelectExecutionPlan::ReturnedColumnList& cols = csep->returnedCols();
CalpontSelectExecutionPlan::ReturnedColumnList::const_iterator iter;
ReturnedColumn* rc;
for (iter = cols.begin(); iter != cols.end(); iter++)
{
if ((*iter)->refCount() != 0)
{
rc = dynamic_cast<ReturnedColumn*>(iter->get());
break;
}
}
if (iter == cols.end())
{
assert (!cols.empty());
// We take cols[0] here due to the optimization happening in
// derivedTableOptimization. All cols with refCount 0 from
// the end of the cols list are optimized out, until the
// first column with non-zero refCount is encountered. So
// here, if instead of cols[0], we take cols[1] (based on
// some logic) and increment it's refCount, then cols[0] is
// not optimized out in derivedTableOptimization and is
// added as a ConstantColumn to the derived table's returned
// column list. This later causes an ineffective row group
// with row of the form (1, cols[1]_value1) to be created in ExeMgr.
rc = dynamic_cast<ReturnedColumn*>(cols[0].get());
// @bug5634 derived table optimization.
rc->incRefCount();
}
SimpleColumn* sc = new SimpleColumn();
sc->columnName(rc->alias());
sc->sequence(0);
sc->tableAlias(tan.alias);
sc->timeZone(gwi.thd->variables.time_zone->get_name()->ptr());
// @bug5634 derived table optimization.
rc->incRefCount();
sc->derivedTable(csep->derivedTbAlias());
sc->derivedRefCol(rc);
return sc;