plucky (3) PQgetvf.3.gz

NAME

       PQgetf - Gets one or more values from a PGresult in a scanf fashion.

SYNOPSIS

       #include <libpqtypes.h>

       int PQgetf(const PGresult *res, int tup_num,
                  const char *format, ...);
       int PQgetvf(const PGresult *res, int tup_num,
                  const char *format, va_list ap);

DESCRIPTION

       The  PQgetf()  and  PQgetvf()  functions get one or more field values from a PGresult using a scanf style
       interface.  The tup_num argument indicates which tuple to read values from; values can only be read  from
       one tuple at a time.

       The  format  argument  is  a  data type specifier string indicating the values to retrieve, like %int4 or
       #timestamp.  Any number of fields, in any order, can be retrieved in  a  single  call.   Each  data  type
       specifier  has  a  cooresponding  field_num,  type-args,  [...]  contained within the function´s variable
       argument list.  The field_num either indicates tuple field number  or  tuple  field  name,  depending  on
       whether  the data type in format used a ´%´ or ´#´ specifer mark (`man pqt-specs(3)´).  The type-args can
       be one or more arguments required by the specific data type: for example, "%int4" would require a pointer
       to a PGint4.  All built-in PostgreSQL data types require a single pointer value.

RETURN VALUE

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

       If the retrieval of any field fails, the get operation is aborted and  function  will  fail.   Eventhough
       some  fields  may have succeeded prior to the failure, their values should not be trusted.  Instead, make
       another PQgetf() call.  Getting an array or a composite can lead to memory leaks when getf  fails.   This
       is  because  these  types  allocate  a  PGresult  object  that  must  be  cleared.  To avoid leaks, it is
       recommended to perform cleanup even if getf fails, retrieve arrays and composites by themselves  or  make
       them the last field in a getf call.

EXAMPLES

   Using PQgetf on a PGresult
       The  example  uses  the libpq PQexec function to execute a query and then uses PQgetf() to retrieve field
       values.  It is important to note that libpqtypes execution functions, like PQparamExec(3), do not need to
       generate the PGresult provided to PQgetf().

              int success;
              PGint4 i4;
              PGtext text;
              PGbytea bytea;
              PGpoint pt;
              PGresult *res = PQexec(conn, "SELECT i,t,b,p FROM tbl");

              /* Get some field values from the result (order doesn´t matter) */
              success = PQgetf(res,
                   0,            /* get field values from tuple 0 */
                   "%int4 #text %bytea %point",
                                 /* type format specifiers (get text by name ´#´) */
                   0,   &i4,     /* get an int4 from field num 0 */
                   "t", &text,   /* get a text from field name "t" */
                   2,   &bytea,  /* get a bytea from field num 2 */
                   3,   &pt);    /* get a point from field num 3 */

              /* Output an error message using PQgeterror(3). */
              if(!success)
                   fprintf(stderr, "*ERROR: %s\n", PQgeterror());

              /* Output the values, do this before PQclear() */
              else
                   printf("int4=%d, text=%s, bytea=%d bytes, point=(%f,%f)\n",
                        i4, text, bytea.len, pt.x, pt.y);

              PQclear(res);

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) 2011 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), PQgeterror(3)