storage_engine.cpp

#include <algorithm>
#include "storage_engine.h"

bool Value::operator==(const Value &other) const {
    if (this->data_type != other.data_type)
        return false;
    if (this->data_type == ColumnAttribute::INT)
        return this->n == other.n;
    return this->s == other.s;
}

bool Value::operator!=(const Value &other) const {
    return !(*this == other);
}

bool Value::operator<(const Value &other) const {
    if (this->data_type != other.data_type) {
        // arbitrary ordering of data types: BOOLEAN < INT < TEXT
        if (this->data_type == ColumnAttribute::BOOLEAN)
            return true;
        if (other.data_type == ColumnAttribute::BOOLEAN)
            return false;
        if (this->data_type == ColumnAttribute::INT)
            return true;
        if (other.data_type == ColumnAttribute::INT)
            return false;
        return false; // should never reach this
    }
    if (this->data_type == ColumnAttribute::TEXT)
        return this->s < other.s;
    return this->n < other.n;
}

// Get only selected column attributes
ColumnAttributes* DbRelation::get_column_attributes(const ColumnNames &select_column_names) const {
    ColumnAttributes *ret = new ColumnAttributes();
    for (auto const& column_name: select_column_names) {
        auto it = std::find(this->column_names.begin(), this->column_names.end(), column_name);
        if (it == this->column_names.end()) {
            delete ret;
            throw DbRelationError("unknown column " + column_name);
        }
        ptrdiff_t index = it - this->column_names.begin();
        ret->push_back(this->column_attributes[index]);
    }
    return ret;
}

// Just pulls out the column names from a ValueDict and passes that to the usual form of project().
ValueDict* DbRelation::project(Handle handle, const ValueDict* where) {
    ColumnNames t;
    for (auto const& column: *where)
        t.push_back(column.first);
    return this->project(handle, &t);
}


// Do a projection for each of a list of handles
ValueDicts* DbRelation::project(Handles *handles) {
    ValueDicts *ret = new ValueDicts();
    for (auto const& handle: *handles)
        ret->push_back(project(handle));
    return ret;
}

// Do a projection for each of a list of handles
ValueDicts* DbRelation::project(Handles *handles, const ColumnNames *column_names) {
    ValueDicts *ret = new ValueDicts();
    for (auto const& handle: *handles)
        ret->push_back(project(handle, column_names));
    return ret;
}

// Do a projection for each of a list of handles
ValueDicts* DbRelation::project(Handles *handles, const ValueDict* where) {
    ColumnNames t;
    for (auto const& column: *where)
        t.push_back(column.first);
    ValueDicts *ret = new ValueDicts();
    for (auto const& handle: *handles)
        ret->push_back(project(handle, &t));
    return ret;
}