usql/executor.cpp

#include "executor.h"
#include "exception.h"

#include <algorithm>


Executor::Executor() {
    m_tables.clear();
}

Table* Executor::find_table(const std::string name) {
    auto name_cmp = [name](Table t){ return t.m_name == name; };
    auto table_def = std::find_if(begin(m_tables), end(m_tables), name_cmp );
    if (table_def != std::end(m_tables)) {
        return table_def.operator->();
    } else {
        throw Exception("table not found (" + name + ")");
    }
}


bool Executor::execute(Node& node) {
    // TODO optimize node here
    switch (node.node_type) {
        case NodeType::create_table:
            return execute_create_table(static_cast<CreateTableNode &>(node));
        case NodeType::insert_into:
            return execute_insert_into_table(static_cast<InsertIntoTableNode &>(node));
        case NodeType::select_from:
            return execute_select(static_cast<SelectFromTableNode &>(node));
        default:
            // TODO error message
            return false;
    }

}

bool Executor::execute_create_table(CreateTableNode& node) {
    // TODO check table does not exists
    Table table{node.table_name, node.cols_defs};
    m_tables.push_back(table);

    return true;
}

bool Executor::execute_insert_into_table(InsertIntoTableNode& node) {
    // TODO check column names.size = values.size

    // find table
    Table* table_def = find_table(node.table_name);

    // prepare empty new_row
    Row new_row = table_def->createEmptyRow();

    // copy values
    for(size_t i=0; i<node.cols_names.size(); i++) {
        auto colNameNode = node.cols_names[i];
        ColDefNode col_def = table_def->get_column_def(colNameNode.name);

        // TODO validate value
        
        if (col_def.type == ColumnType::integer_type) {
            new_row.setColumnValue(col_def.order, std::stoi(node.cols_values[i].value));
        } else if (col_def.type == ColumnType::float_type) {
            new_row.setColumnValue(col_def.order, std::stof(node.cols_values[i].value));
        } else {
            new_row.setColumnValue(col_def.order, node.cols_values[i].value);
        }
    }

    // TODO check not null columns

    // append new_row
    table_def->addRow(new_row);

    return true;
}

bool Executor::execute_select(SelectFromTableNode& node) {
    // TODO create plan for accessing rows

    // find source table
    Table* table = find_table(node.table_name);

    // create result table
    std::vector<ColDefNode> result_tbl_col_defs{};
    std::vector<int> source_table_col_index{};
    int i = 0;  // new column order
    for(ColNameNode rc : node.cols_names) {
        ColDefNode cdef = table->get_column_def(rc.name);
        source_table_col_index.push_back(cdef.order);

        auto col = ColDefNode(rc.name, cdef.type, i, cdef.length, cdef.null);
        result_tbl_col_defs.push_back(col);

        i++;
    }
    Table result {"result", result_tbl_col_defs};


    // execute access plan


    for (auto row = begin (table->m_rows); row != end (table->m_rows); ++row) {
        // eval where for row
        bool where_true = true;
        if (node.where->node_type == NodeType::true_node) {    // no where clause
            where_true = true;
        } else {    // evaluate where
            RelationalOperatorNode& filter = static_cast<RelationalOperatorNode &>(*node.where);
            if (filter.op == RelationalOperatorType::greater) {
                std::unique_ptr<Node> left_value;
                if ((*filter.left).node_type == NodeType::database_value) {
                    DatabaseValueNode *dvl = static_cast<DatabaseValueNode*>(filter.left.get());
                    ColDefNode col_def = table->get_column_def(dvl->col_name); // TODO optimize it to just get this def once
                    auto db_value = row->ithColum(col_def.order);
                    if (col_def.type == ColumnType::integer_type) {
                        left_value = std::make_unique<IntValueNode>(db_value->integerValue());
                    }
                    // TODO other cases
                }

                std::unique_ptr<Node> right_value;
                if ((*filter.right).node_type == NodeType::int_value) {
                    IntValueNode *ivl = static_cast<IntValueNode*>(filter.right.get());
                    right_value = std::make_unique<IntValueNode>(ivl->value);
                }

                IntValueNode* left_int_value = static_cast<IntValueNode *>(left_value.get());
                IntValueNode* right_int_value = static_cast<IntValueNode *>(right_value.get());

                where_true = left_int_value->value > right_int_value->value;
            }
        }

        if (where_true) {
            // prepare empty row
            Row new_row = result.createEmptyRow();

            // copy column values
            for(auto idx=0; idx<result.columns_count(); idx++) {
                auto row_col_index = source_table_col_index[idx];
                ColValue *col_value = row->ithColum(row_col_index);
                if (result_tbl_col_defs[idx].type == ColumnType::integer_type)
                    new_row.setColumnValue(idx, ((ColIntegerValue*)col_value)->integerValue());
                if (result_tbl_col_defs[idx].type == ColumnType::float_type)
                    new_row.setColumnValue(idx, col_value->floatValue());
                if (result_tbl_col_defs[idx].type == ColumnType::varchar_type)
                    new_row.setColumnValue(idx, col_value->stringValue());
            }

            // add row to result
            result.m_rows.push_back(new_row);
        }
    }

    result.print();

    return true;
}