How to read an array of pairs result from libpqxx into C++












0















I have a postgresfunction returning the type tp_m_info wich contains
an array of pairs (see below). And i'm using libpqxx to connecting to
postgres.



CREATE TYPE public.tp_m_set_id AS

(

    m_id integer,

    m_name text

);





CREATE TYPE public.tp_m_info AS

(

    m_id integer,

    m_name text,

    m_value double precision,

    m_is_true boolean,

    original_ms tp_m_set_id

);


I can read int, double, str and even boolean from the result:



iter[m_id].as<int>()

iter[m_name].c_str()

iter[m_value].as<double>()



// and bool like

std::string tmp_str = iter["m_is_true"].c_str();

if ("t" == tmp_str)

{

    info.m_is_merged = true;

}

else

{

    info.m_is_merged = false;

}


but I don't know how to handle "tp_m_set_id"
It failed with something like "std::vector>"



iter[original_ms].as<std::vector<std::pair<uint32_t, std::string>>>()


Any Idea how to get it?



In "libpq" there is binary resultFormat with:
PQexecParams() and paramFormats=1
see: https://www.postgresql.org/docs/10/libpq-exec.html



Is there a binary Format in "libpqxx" now? Has something changed in
the last 10 years?
see: http://pqxx.org/development/libpqxx/wiki/BinaryTransfers



Is there a fast way to get a block of compound data from libpqxx and
convert it to C++?






c++ postgresql libpqxx







share|improve this question



























    0















    I have a postgresfunction returning the type tp_m_info wich contains
    an array of pairs (see below). And i'm using libpqxx to connecting to
    postgres.



    CREATE TYPE public.tp_m_set_id AS
    
(
    
    m_id integer,
    
    m_name text
    
);
    

    

    
CREATE TYPE public.tp_m_info AS
    
(
    
    m_id integer,
    
    m_name text,
    
    m_value double precision,
    
    m_is_true boolean,
    
    original_ms tp_m_set_id
    
);


    I can read int, double, str and even boolean from the result:



    iter[m_id].as<int>()
    
iter[m_name].c_str()
    
iter[m_value].as<double>()
    

    
// and bool like
    
std::string tmp_str = iter["m_is_true"].c_str();
    
if ("t" == tmp_str)
    
{
    
    info.m_is_merged = true;
    
}
    
else
    
{
    
    info.m_is_merged = false;
    
}


    but I don't know how to handle "tp_m_set_id"
    It failed with something like "std::vector>"



    iter[original_ms].as<std::vector<std::pair<uint32_t, std::string>>>()


    Any Idea how to get it?



    In "libpq" there is binary resultFormat with:
    PQexecParams() and paramFormats=1
    see: https://www.postgresql.org/docs/10/libpq-exec.html



    Is there a binary Format in "libpqxx" now? Has something changed in
    the last 10 years?
    see: http://pqxx.org/development/libpqxx/wiki/BinaryTransfers



    Is there a fast way to get a block of compound data from libpqxx and
    convert it to C++?






    c++ postgresql libpqxx







    share|improve this question

























      0












      0








      0








      I have a postgresfunction returning the type tp_m_info wich contains
      an array of pairs (see below). And i'm using libpqxx to connecting to
      postgres.



      CREATE TYPE public.tp_m_set_id AS
      
(
      
    m_id integer,
      
    m_name text
      
);
      

      

      
CREATE TYPE public.tp_m_info AS
      
(
      
    m_id integer,
      
    m_name text,
      
    m_value double precision,
      
    m_is_true boolean,
      
    original_ms tp_m_set_id
      
);


      I can read int, double, str and even boolean from the result:



      iter[m_id].as<int>()
      
iter[m_name].c_str()
      
iter[m_value].as<double>()
      

      
// and bool like
      
std::string tmp_str = iter["m_is_true"].c_str();
      
if ("t" == tmp_str)
      
{
      
    info.m_is_merged = true;
      
}
      
else
      
{
      
    info.m_is_merged = false;
      
}


      but I don't know how to handle "tp_m_set_id"
      It failed with something like "std::vector>"



      iter[original_ms].as<std::vector<std::pair<uint32_t, std::string>>>()


      Any Idea how to get it?



      In "libpq" there is binary resultFormat with:
      PQexecParams() and paramFormats=1
      see: https://www.postgresql.org/docs/10/libpq-exec.html



      Is there a binary Format in "libpqxx" now? Has something changed in
      the last 10 years?
      see: http://pqxx.org/development/libpqxx/wiki/BinaryTransfers



      Is there a fast way to get a block of compound data from libpqxx and
      convert it to C++?






      c++ postgresql libpqxx







      share|improve this question














      I have a postgresfunction returning the type tp_m_info wich contains
      an array of pairs (see below). And i'm using libpqxx to connecting to
      postgres.



      CREATE TYPE public.tp_m_set_id AS
      
(
      
    m_id integer,
      
    m_name text
      
);
      

      

      
CREATE TYPE public.tp_m_info AS
      
(
      
    m_id integer,
      
    m_name text,
      
    m_value double precision,
      
    m_is_true boolean,
      
    original_ms tp_m_set_id
      
);


      I can read int, double, str and even boolean from the result:



      iter[m_id].as<int>()
      
iter[m_name].c_str()
      
iter[m_value].as<double>()
      

      
// and bool like
      
std::string tmp_str = iter["m_is_true"].c_str();
      
if ("t" == tmp_str)
      
{
      
    info.m_is_merged = true;
      
}
      
else
      
{
      
    info.m_is_merged = false;
      
}


      but I don't know how to handle "tp_m_set_id"
      It failed with something like "std::vector>"



      iter[original_ms].as<std::vector<std::pair<uint32_t, std::string>>>()


      Any Idea how to get it?



      In "libpq" there is binary resultFormat with:
      PQexecParams() and paramFormats=1
      see: https://www.postgresql.org/docs/10/libpq-exec.html



      Is there a binary Format in "libpqxx" now? Has something changed in
      the last 10 years?
      see: http://pqxx.org/development/libpqxx/wiki/BinaryTransfers



      Is there a fast way to get a block of compound data from libpqxx and
      convert it to C++?






      c++ postgresql libpqxx




      c++ postgresql libpqxx






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 28 '18 at 11:06









      M. XX.M. XX.

      1




      1
























          1 Answer
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          0














          I guess the solution is



          e.g. to use:



          std::pair<int, int> my_pair = row["m_ints"].as<std::pair<int, int> >();


          write into strconv.hxx:



          template<> struct PQXX_LIBEXPORT string_traits<std::pair<int, int> >
          
{                                   
          
static constexpr const char *name() noexcept { return "std::pair<int, int>"; }
          
static constexpr bool has_null() noexcept { return false; }     
          
static bool is_null(std::pair<int, int>) { return false; }
          
[[noreturn]] static std::pair<int, int> null()
          
{ internal::throw_null_conversion(name()); }            
          
static void from_string(const char Str, std::pair<int, int> &Obj);
          
static std::string to_string(std::pair<int, int> Obj);
          
};


          and in strconv.cxx implement:




          • static void from_string(const char Str, std::pair &Obj);

          • static std::string to_string(std::pair Obj);


          now you have to recompile libpqxx.



          The problem is, the implementation of "from_string" ends up in stringparsing a string like "(9,5)". And Stringparsing is not what i want.



          so i'm going to try libpq.






          share|improve this answer























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            1 Answer
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            1 Answer
            1






            active

            oldest

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            active

            oldest

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            active

            oldest

            votes









            0














            I guess the solution is



            e.g. to use:



            std::pair<int, int> my_pair = row["m_ints"].as<std::pair<int, int> >();


            write into strconv.hxx:



            template<> struct PQXX_LIBEXPORT string_traits<std::pair<int, int> >
            
{                                   
            
static constexpr const char *name() noexcept { return "std::pair<int, int>"; }
            
static constexpr bool has_null() noexcept { return false; }     
            
static bool is_null(std::pair<int, int>) { return false; }
            
[[noreturn]] static std::pair<int, int> null()
            
{ internal::throw_null_conversion(name()); }            
            
static void from_string(const char Str, std::pair<int, int> &Obj);
            
static std::string to_string(std::pair<int, int> Obj);
            
};


            and in strconv.cxx implement:




            • static void from_string(const char Str, std::pair &Obj);

            • static std::string to_string(std::pair Obj);


            now you have to recompile libpqxx.



            The problem is, the implementation of "from_string" ends up in stringparsing a string like "(9,5)". And Stringparsing is not what i want.



            so i'm going to try libpq.






            share|improve this answer




























              0














              I guess the solution is



              e.g. to use:



              std::pair<int, int> my_pair = row["m_ints"].as<std::pair<int, int> >();


              write into strconv.hxx:



              template<> struct PQXX_LIBEXPORT string_traits<std::pair<int, int> >
              
{                                   
              
static constexpr const char *name() noexcept { return "std::pair<int, int>"; }
              
static constexpr bool has_null() noexcept { return false; }     
              
static bool is_null(std::pair<int, int>) { return false; }
              
[[noreturn]] static std::pair<int, int> null()
              
{ internal::throw_null_conversion(name()); }            
              
static void from_string(const char Str, std::pair<int, int> &Obj);
              
static std::string to_string(std::pair<int, int> Obj);
              
};


              and in strconv.cxx implement:




              • static void from_string(const char Str, std::pair &Obj);

              • static std::string to_string(std::pair Obj);


              now you have to recompile libpqxx.



              The problem is, the implementation of "from_string" ends up in stringparsing a string like "(9,5)". And Stringparsing is not what i want.



              so i'm going to try libpq.






              share|improve this answer


























                0












                0








                0







                I guess the solution is



                e.g. to use:



                std::pair<int, int> my_pair = row["m_ints"].as<std::pair<int, int> >();


                write into strconv.hxx:



                template<> struct PQXX_LIBEXPORT string_traits<std::pair<int, int> >
                
{                                   
                
static constexpr const char *name() noexcept { return "std::pair<int, int>"; }
                
static constexpr bool has_null() noexcept { return false; }     
                
static bool is_null(std::pair<int, int>) { return false; }
                
[[noreturn]] static std::pair<int, int> null()
                
{ internal::throw_null_conversion(name()); }            
                
static void from_string(const char Str, std::pair<int, int> &Obj);
                
static std::string to_string(std::pair<int, int> Obj);
                
};


                and in strconv.cxx implement:




                • static void from_string(const char Str, std::pair &Obj);

                • static std::string to_string(std::pair Obj);


                now you have to recompile libpqxx.



                The problem is, the implementation of "from_string" ends up in stringparsing a string like "(9,5)". And Stringparsing is not what i want.



                so i'm going to try libpq.






                share|improve this answer













                I guess the solution is



                e.g. to use:



                std::pair<int, int> my_pair = row["m_ints"].as<std::pair<int, int> >();


                write into strconv.hxx:



                template<> struct PQXX_LIBEXPORT string_traits<std::pair<int, int> >
                
{                                   
                
static constexpr const char *name() noexcept { return "std::pair<int, int>"; }
                
static constexpr bool has_null() noexcept { return false; }     
                
static bool is_null(std::pair<int, int>) { return false; }
                
[[noreturn]] static std::pair<int, int> null()
                
{ internal::throw_null_conversion(name()); }            
                
static void from_string(const char Str, std::pair<int, int> &Obj);
                
static std::string to_string(std::pair<int, int> Obj);
                
};


                and in strconv.cxx implement:




                • static void from_string(const char Str, std::pair &Obj);

                • static std::string to_string(std::pair Obj);


                now you have to recompile libpqxx.



                The problem is, the implementation of "from_string" ends up in stringparsing a string like "(9,5)". And Stringparsing is not what i want.



                so i'm going to try libpq.







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Nov 29 '18 at 14:56









                M. XX.M. XX.

                1




                1
































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