/* LiteSQL  *  * By Tero Laitinen  *  * See LICENSE for copyright information. *//** \file backend.hpp    Classes Backend, Backend::Cursor and Backend::Result*/#ifndef _litesql_backend_hpp#define _litesql_backend_hpp#include <memory>#include "litesql/types.hpp"namespace litesql {using namespace std;/** An abstract base class for interfacing with relational databases */class Backend {public:    /** An abstract base class for cursors that iterate result sets        returned by relational database */    class Cursor {    public:        /** empty */        virtual ~Cursor() {}        /** if inherited Cursor can cache its data to speed up             iteration, this method is used to set cache size.             All backends do not react to this request.        */        virtual void setCacheSize(int s) {}        /** returns one result row. empty row means that result set is          *  iterated through */        virtual Record fetchOne()=0;      };    class Result {    public:        /** empty */        virtual ~Result() {}        /** returns number of columns (fields) in result set */        virtual size_t fieldNum() const=0;        /** returns names of columns (fields) of the result set */        virtual Record fields() const=0;        /** returns number of rows (records) in result set */        virtual size_t recordNum() const=0;        /** returns result set */        virtual Records records() const=0;    };    /** empty */    virtual ~Backend() {}    /** return true if backend supports CREATE SEQUENCE -        SQL-statements */    virtual bool supportsSequences() const {        return false;    }    /** backend may want to set an AUTO_INCREMENT-attribute for table's primary        key field. this method is to deliver the details to database schema */    virtual string getRowIDType() const {        return "INTEGER PRIMARY KEY";    }    /** if backend supports this, new primary key of the last insert        is returned */    virtual string getInsertID() const { return ""; }    /** begin SQL transaction, may or may not have an effect */    virtual void begin() const {}    /** commit SQL transaction */    virtual void commit() const {}    /** rollback SQL transaction */    virtual void rollback() const {}    /** executes SQL-query        \param query SQL-query to execute        \return Result-object which holds result set of query */    virtual Result* execute(string query) const = 0;    /** executes SQL-query        \param query SQL-query to execute         \return Cursor-object which can be used to iterate result set                 row by row without loading everything to memory */    virtual Cursor* cursor(string query) const = 0;    /** executes multiple INSERT-statements and assigns same 'row id'        for first field of every record        \param tables destination tables for insert operation        \param fields record of field names per table        \param values record of values per table        \param sequence sequence where row id-numbers are pulled        \return new row id */    virtual string groupInsert(Record tables, Records fields, Records values,                               string sequence) const;};}#endif