SubMain.java

import net.sf.jsqlparser.expression.Expression;
import net.sf.jsqlparser.expression.PrimitiveValue;
import net.sf.jsqlparser.schema.Column;
import net.sf.jsqlparser.schema.Table;
import net.sf.jsqlparser.statement.create.table.CreateTable;
import net.sf.jsqlparser.statement.select.*;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

/**
 * Created by Mugdha on 7/3/2017.
 */
public class SubMain {
    public PlainSelect plainSelect;
    public HashMap<String, CreateTable> createTableMap;
    public Column[] schema;
    public Column[] newSchema;

    public SubMain(PlainSelect plainSelect, HashMap createTableMap){
        this.plainSelect = plainSelect;
        this.createTableMap = createTableMap;
    }
    public ArrayList execute(){
        HashMap<String, HashMap<String, ColumnIdType>> databaseMap = new HashMap<>();
        HashMap<PrimitiveValue,ArrayList<PrimitiveValue[]>> groupByMap = new HashMap<>();
        ArrayList<PrimitiveValue[]> outputTupleList = new ArrayList<>();

        HashMap<String, String> aliasHashMap;
        HashMap<String, Operator> operatorMap;
        List<Join> joinList;
        Operator oper = null;

        FromScanner fromscan = new FromScanner(createTableMap);
        plainSelect.getFromItem().accept(fromscan);

        if(plainSelect.getJoins() != null) {
            joinList = plainSelect.getJoins();
            for(Join join : joinList) {
                join.getRightItem().accept(fromscan);
            }
        } else {

        }
        aliasHashMap = fromscan.aliasHasMap;
        operatorMap = fromscan.operatorMap;
        schema = new Column[fromscan.schemaList.size()];
        schema = fromscan.schemaList.toArray(schema);
        createTableMap = fromscan.createTableMap;
        if(plainSelect.getWhere() != null) {
            oper = new SelectionOperator(
                    databaseMap,
                    operatorMap,
                    schema,
                    plainSelect.getWhere(),
                    aliasHashMap,
                    createTableMap
            );
        } else {
            for (String key : operatorMap.keySet()) {
                oper = operatorMap.get(key);
            }
        }

        //group by
        if(plainSelect.getGroupByColumnReferences()!=null){
            List<Column> groupByColumns = plainSelect.getGroupByColumnReferences();
            PrimitiveValue[] tuple = oper.readOneTuple();
            GroupByOperator groupByOperator = new GroupByOperator(schema, groupByColumns, aliasHashMap);
            while(tuple!=null){
                groupByOperator.groupTuples(tuple);
                tuple = oper.readOneTuple();
            }
            groupByMap = groupByOperator.groupByMap;
            outputTupleList = groupByOperator.getGroupByOutput();
        }
        else{
            PrimitiveValue[] tuple = oper.readOneTuple();
            while(tuple!=null){
                outputTupleList.add(tuple);
                tuple = oper.readOneTuple();
            }
        }

        //Check for aggregate condition in SELECT


        // Having
        if(plainSelect.getHaving()!=null){
            Expression condition = plainSelect.getHaving();
            HavingOperator havingOperator = new HavingOperator(condition, groupByMap, aliasHashMap, schema);
            havingOperator.filterGroupedEle();
            outputTupleList = havingOperator.getHavingOutput();
            groupByMap = havingOperator.getMap();
        }

        //Order By
        if(plainSelect.getOrderByElements()!=null){
            List<OrderByElement> orderByList = plainSelect.getOrderByElements();
            OrderByOperator orderByOperator = new OrderByOperator(
                    groupByMap, aliasHashMap, schema, plainSelect, outputTupleList
            );
            orderByOperator.orderTuples(orderByList);
            outputTupleList = orderByOperator.getOrderByOutput();
            groupByMap = orderByOperator.groupByMap;
        }

        List<SelectItem> selectItemList = plainSelect.getSelectItems();
        ProjectionOperator projectionOperator = new ProjectionOperator(
                outputTupleList, selectItemList, schema, aliasHashMap
        );
        outputTupleList = projectionOperator.getProjectedOutput();
        newSchema = projectionOperator.newSchema;
        Distinct distinct = plainSelect.getDistinct();
        if(distinct != null){
            DistinctOperator distinctOperator = new DistinctOperator(outputTupleList);
            outputTupleList = distinctOperator.execute();
        }


        return outputTupleList;
    }
}