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

/* Copyright (C) 2014 InfiniDB, Inc.
   Copyright (C) 2016 MariaDB Corporaton

   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 Street, Fifth Floor, Boston,
   MA 02110-1301, USA. */

/***********************************************************************
*   $Id: ha_from_sub.cpp 6377 2010-03-22 20:18:47Z zzhu $
*
*
***********************************************************************/
/** @file */
/** class FromSubSelect definition */

//#define NDEBUG
#include <my_config.h>
#include <cassert>
#include <map>
using namespace std;

#include "idb_mysql.h"

#include "parsetree.h"
#include "simplefilter.h"
#include "logicoperator.h"
#include "constantcolumn.h"
#include "simplecolumn.h"
using namespace execplan;

#include "ha_subquery.h"

namespace cal_impl_if
{

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);
	}
}

void setDerivedTable(execplan::ParseTree* n)
{
	ParseTree *lhs = n->left();
	ParseTree *rhs = n->right();

	Operator *op = dynamic_cast<Operator*>(n->data());

	// if logic operator then lhs and rhs can't be both null
	if (op)
	{
		if (!lhs || lhs->derivedTable() == "*")
		{
			n->derivedTable(rhs ? rhs->derivedTable() : "*");
		}
		else if (!rhs || rhs->derivedTable() == "*")
		{
			n->derivedTable(lhs->derivedTable());
		}
		else if (lhs->derivedTable() == rhs->derivedTable())
		{
			n->derivedTable(lhs->derivedTable());
		}
		else
		{
			n->derivedTable("");
		}
	}
	else
	{
		n->data()->setDerivedTable();
		n->derivedTable(n->data()->derivedTable());
	}
}

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;
}

FromSubQuery::FromSubQuery(gp_walk_info& gwip) : SubQuery(gwip)
{}

FromSubQuery::FromSubQuery(gp_walk_info& gwip, SELECT_LEX* sub) :
	SubQuery(gwip),
	fFromSub(sub)
{}

FromSubQuery::~FromSubQuery()
{}

SCSEP FromSubQuery::transform()
{
	assert (fFromSub);
	SCSEP csep(new CalpontSelectExecutionPlan());
	csep->sessionID(fGwip.sessionid);
	csep->location(CalpontSelectExecutionPlan::FROM);
	csep->subType (CalpontSelectExecutionPlan::FROM_SUBS);

	// gwi for the sub query
	gp_walk_info gwi;
	gwi.thd = fGwip.thd;
	gwi.subQuery = this;
	gwi.viewName = fGwip.viewName;
	csep->derivedTbAlias(fAlias); // always lower case

	if (getSelectPlan(gwi, *fFromSub, csep) != 0)
	{
		fGwip.fatalParseError = true;
		if (!gwi.parseErrorText.empty())
			fGwip.parseErrorText = gwi.parseErrorText;
		else
			fGwip.parseErrorText = "Error occured in FromSubQuery::transform()";
		csep.reset();
		return csep;
	}
	fGwip.subselectList.push_back(csep);
	return csep;
}

}