void derivedTableOptimization(SCSEP& csep)
{
// @bug5634. replace the unused column with ConstantColumn from derived table column list,
// ExeMgr will not project ConstantColumn. Only count for local derived column.
// subquery may carry main query derived table list for column reference, those
// derived tables are not checked for optimization in this scope.
CalpontSelectExecutionPlan::SelectList derivedTbList = csep->derivedTableList();
// @bug6156. Skip horizontal optimization for no table union.
bool horizontalOptimization = true;
for (uint i = 0; i < derivedTbList.size(); i++)
{
CalpontSelectExecutionPlan* plan = dynamic_cast<CalpontSelectExecutionPlan*>(derivedTbList[i].get());
CalpontSelectExecutionPlan::ReturnedColumnList cols = plan->returnedCols();
vector<CalpontSelectExecutionPlan::ReturnedColumnList> unionColVec;
// only do vertical optimization for union all
// @bug6134. Also skip the vertical optimization for select distinct
// because all columns need to be projected to check the distinctness.
bool verticalOptimization = false;
if (plan->distinctUnionNum() == 0 && !plan->distinct())
{
verticalOptimization = true;
for (uint j = 0; j < plan->unionVec().size(); j++)
{
unionColVec.push_back(
dynamic_cast<CalpontSelectExecutionPlan*>(plan->unionVec()[j].get())->returnedCols());
}
}
if (plan->tableList().empty())
horizontalOptimization = false;
for (uint j = 0; j < plan->unionVec().size(); j++)
{
if (dynamic_cast<CalpontSelectExecutionPlan*>(plan->unionVec()[j].get())->tableList().empty())
{
horizontalOptimization = false;
break;
}
}
if (verticalOptimization)
{
int64_t val = 1;
for (uint i = 0; i < cols.size(); i++)
{
//if (cols[i]->derivedTable().empty())
if (cols[i]->refCount() == 0)
{
if (cols[i]->derivedRefCol())
cols[i]->derivedRefCol()->decRefCount();
cols[i].reset(new ConstantColumn(val));
for (uint j = 0; j < unionColVec.size(); j++)
unionColVec[j][i].reset(new ConstantColumn(val));
}
}
// set back
plan->returnedCols(cols);
for (uint j = 0; j < unionColVec.size(); j++)
dynamic_cast<CalpontSelectExecutionPlan*>(plan->unionVec()[j].get())->returnedCols(unionColVec[j]);
}
}
/*
* @bug5635. Move filters that only belongs to a derived table to inside the derived table.
* 1. parse tree walk to populate derivedTableFilterMap and set null candidate on the tree.
* 2. remove the null filters
* 3. and the filters of derivedTableFilterMap and append to the WHERE filter of the derived table
*
* Note:
* 1. Subquery filters is ignored because derived table can not be in subquery
* 2. While walking tree, whenever a single derive simplefilter is encountered,
* this filter is pushed to the corresponding stack
* 2. Whenever an OR operator is encountered, all the filter stack of
* that OR involving derived table are emptied and null candidate of each
* stacked filter needs to be reset (not null)
*/
ParseTree* pt = csep->filters();
map<string, ParseTree*> derivedTbFilterMap;
if (horizontalOptimization && pt)
{
pt->walk(setDerivedTable);
setDerivedFilter(pt, derivedTbFilterMap, derivedTbList);
csep->filters(pt);
}
// AND the filters of individual stack to the derived table filter tree
// @todo union filters.
// @todo outer join complication
map<string, ParseTree*>::iterator mapIt;
for (uint i = 0; i < derivedTbList.size(); i++)
{
CalpontSelectExecutionPlan* plan = dynamic_cast<CalpontSelectExecutionPlan*>(derivedTbList[i].get());
CalpontSelectExecutionPlan::ReturnedColumnList derivedColList = plan->returnedCols();
mapIt = derivedTbFilterMap.find(plan->derivedTbAlias());
if (mapIt != derivedTbFilterMap.end())
{
// replace all derived column of this filter with real column from
// derived table projection list.
ParseTree* mainFilter = new ParseTree();
mainFilter->copyTree(*(mapIt->second));
replaceRefCol(mainFilter, derivedColList);
ParseTree* derivedFilter = plan->filters();
if (derivedFilter)
{
LogicOperator* op = new LogicOperator("and");
ParseTree* filter = new ParseTree(op);
filter->left(derivedFilter);
filter->right(mainFilter);
plan->filters(filter);
}
else
{
plan->filters(mainFilter);
}
// union filter handling
for (uint j = 0; j < plan->unionVec().size(); j++)
{
CalpontSelectExecutionPlan* unionPlan =
dynamic_cast<CalpontSelectExecutionPlan*>(plan->unionVec()[j].get());
CalpontSelectExecutionPlan::ReturnedColumnList unionColList = unionPlan->returnedCols();
ParseTree* mainFilterForUnion = new ParseTree();
mainFilterForUnion->copyTree(*(mapIt->second));
replaceRefCol(mainFilterForUnion, unionColList);
ParseTree* unionFilter = unionPlan->filters();
if (unionFilter)
{
LogicOperator* op = new LogicOperator("and");
ParseTree* filter = new ParseTree(op);
filter->left(unionFilter);
filter->right(mainFilterForUnion);
unionPlan->filters(filter);
}
else
{
unionPlan->filters(mainFilterForUnion);
}
}
}
}
// clean derivedTbFilterMap because all the filters are copied
for ( mapIt = derivedTbFilterMap.begin(); mapIt != derivedTbFilterMap.end(); ++mapIt )
delete (*mapIt).second;
// recursively process the nested derived table
for (uint i = 0; i < csep->subSelectList().size(); i++)
{
SCSEP subselect(boost::dynamic_pointer_cast<CalpontSelectExecutionPlan>(csep->subSelectList()[i]));
derivedTableOptimization(subselect);
}
}
ParseTree* setDerivedFilter(ParseTree*& n, map<string, ParseTree*>& filterMap,
CalpontSelectExecutionPlan::SelectList& derivedTbList)
{
if (!(n->derivedTable().empty()))
{
// @todo replace virtual column of n to real column
// all simple columns should belong to the same derived table
CalpontSelectExecutionPlan* csep = NULL;
for (uint i = 0; i < derivedTbList.size(); i++)
{
CalpontSelectExecutionPlan* plan = dynamic_cast<CalpontSelectExecutionPlan*>(derivedTbList[i].get());
if (plan->derivedTbAlias() == n->derivedTable())
{
csep = plan;
break;
}
}
// should never be null; if null then give up optimization.
if (!csep)
return n;
// 2. push the filter to the derived table filter stack, or 'and' with
// the filters in the stack
map<string, ParseTree*>::iterator mapIter = filterMap.find(n->derivedTable());
if ( mapIter == filterMap.end())
{
filterMap.insert(pair<string, ParseTree*>(n->derivedTable(), n));
}
else
{
ParseTree* pt = new ParseTree(new LogicOperator("and"));
pt->left(mapIter->second);
pt->right(n);
mapIter->second = pt;
}
int64_t val = 1;
n = new ParseTree(new ConstantColumn(val));
}
else
{
Operator* op = dynamic_cast<Operator*>(n->data());
if (op && (op->op() == OP_OR || op->op() == OP_XOR))
{
return n;
}
else
{
ParseTree* lhs = n->left();
ParseTree* rhs = n->right();
if (lhs)
n->left(setDerivedFilter(lhs, filterMap, derivedTbList));
if (rhs)
n->right(setDerivedFilter(rhs, filterMap, derivedTbList));
}
}
return n;
}