PQputf(3)                      libpqtypes Manual                     PQputf(3)



NAME
       PQputf, PQputvf - Packs a set of parameters in a PGparam for use with a
       parameterized query.

SYNOPSIS
       #include <libpqtypes.h>

       int PQputf(PGparam *param, const char *spec, ...);
       int PQputvf(PGparam *param, char *stmtBuf, size_t stmtBufLen,
                   const char *spec, va_list ap);

DESCRIPTION
       The PQputf() and PQputvf() functions put one or more  query  parameters
       into  a  PGparam using a printf style interface.  Any number of parame-
       ters can be put at the same time.

       The spec argument is a data type specifier string indicating the param-
       eters  being  put, such as "%int4 %polygon".  spec cannot be NULL or an
       empty string.  The variable argument list must match the  spec,  either
       "..."  or  ap.   The number of arguments required for each data type is
       dependant on the data type itself;  built-in  PostgreSQL  types  always
       require a single argument.

       The PQputvf() function can contruct a parameterized command string from
       spec, as long as stmtBuf and stmtBufLen have  been  provided.   If  the
       construction  of stmtBuf is not desired, set it to NULL and set stmtBu-
       fLen to 0.  When a constructed statement is desired,  the  contents  of
       spec  will  be  copied  to  stmtBuf  and all data type specifiers, like
       "%int4", will be replaced with $1, $2, etc...  syntax.  The result is a
       parameterized  statement  in synch with param and ready to be executed.
       For instance: if spec is "SELECT %int4 + %int4", the resulting  stmtBuf
       would be "SELECT $1 + $2".

RETURN VALUE
       On  success,  a non-zero value is returned.  On error, zero is returned
       and PQgeterror(3) will contain an error message.

       If any put operation fails, the param is reverted back to the number of
       parameters  it  had  prior  to  the function call; partial puts are not
       allowed.

EXAMPLES
   Using PQputf
       The example uses PQputf() to put a couple parameters into a PGparam.

              PGtext text = "foobar";
              PGint8 i8 = PQT_INT64CONST(1099511627776);
              PGparam *param = PQparamCreate(conn);

              if(!PQputf(param, "%text %int8", text, i8))
                   fprintf(stderr, "*ERROR: %s\n", PQgeterror());

              PQparamClear(param);

   Using PQputvf
       The example creates an application function named execf.   execf  is  a
       wrapper to PQputvf(), as well as PQparamExec(3).  This is a very useful
       function but was excluded from libpqtypes because there are  many  dif-
       ferent  ways  of  implementing  it.   For  instance: how stmt buffer or
       PGparam is managed, how errors are handled or  thread-safety  concerns.
       In  the  end,  the  execf  idea  felt more like an application function
       rather than a library one.

              PGresult *
              execf(PGconn *conn, const char *stmtSpec, ...)
              {
                   va_list ap;
                   char stmt[32768];
                   PGparam *param;
                   PGresult *res = NULL;

                   /* create the temporary PGparam */
                   if(!(param = PQparamCreate(conn)))
                        return NULL; /* PQseterror already called */

                   /* put the params, create the stmt and exec it */
                   va_start(ap, stmtSpec);
                   if(PQputvf(param, stmt, sizeof(stmt), stmtSpec, ap))
                        res = PQparamExec(conn, param, stmt, 1); // resfmt is binary
                   va_end(ap);

                   /* param must be cleared */
                   PQparamClear(param);
                   return res;
              }

              /* Example: execf will put 2 ints and execute "SELECT $1 + $2" */
              PGresult *res = execf(conn, "SELECT %int4 + %int4", 100, 67);
              if(!res)
                   fprintf(stderr, "*ERROR: %s\n", PQgeterror());

AUTHOR
       A contribution of eSilo, LLC. for the  PostgreSQL  Database  Management
       System.  Written by Andrew Chernow and Merlin Moncure.

REPORTING BUGS
       Report bugs to <libpqtypes@esilo.com>.

COPYRIGHT
       Copyright (c) 2008 eSilo, LLC. All rights reserved.
       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or  FITNESS FOR A  PARTICULAR
       PURPOSE.

SEE ALSO
       pqt-specs(3), PQparamCreate(3), PQgeterror(3), PQseterror(3)



libpqtypes                           2008                            PQputf(3)

libpqtypes home page