postgresql/src/test/examples/testlibpq3.c

/*
 * testlibpq3.c
 * 	Test the C version of LIBPQ, the POSTGRES frontend library.
 *   tests the binary cursor interface
 *
 *
 *
 populate a database by doing the following:
 
CREATE TABLE test1 (i int4, d float4, p polygon);

INSERT INTO test1 values (1, 3.567, '(3.0, 4.0, 1.0, 2.0)'::polygon);

INSERT INTO test1 values (2, 89.05, '(4.0, 3.0, 2.0, 1.0)'::polygon);

 the expected output is:

tuple 0: got
 i = (4 bytes) 1,
 d = (4 bytes) 3.567000,
 p = (4 bytes) 2 points         boundbox = (hi=3.000000/4.000000, lo = 1.000000,2.000000)
tuple 1: got
 i = (4 bytes) 2,
 d = (4 bytes) 89.050003,
 p = (4 bytes) 2 points         boundbox = (hi=4.000000/3.000000, lo = 2.000000,1.000000)

 *
 */
#include <stdio.h>
#include "libpq-fe.h"
#include "utils/geo-decls.h" /* for the POLYGON type */

void exit_nicely(PGconn* conn)
{
  PQfinish(conn);
  exit(1);
}

main()
{
  char *pghost, *pgport, *pgoptions, *pgtty;
  char* dbName;
  int nFields;
  int i,j;
  int i_fnum, d_fnum, p_fnum;

  PGconn* conn;
  PGresult* res;

  /* begin, by setting the parameters for a backend connection
     if the parameters are null, then the system will try to use
     reasonable defaults by looking up environment variables 
     or, failing that, using hardwired constants */
  pghost = NULL;  /* host name of the backend server */
  pgport = NULL;  /* port of the backend server */
  pgoptions = NULL; /* special options to start up the backend server */
  pgtty = NULL;     /* debugging tty for the backend server */

  dbName = getenv("USER");  /* change this to the name of your test database*/

  /* make a connection to the database */
  conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);

  /* check to see that the backend connection was successfully made */
  if (PQstatus(conn) == CONNECTION_BAD) {
    fprintf(stderr,"Connection to database '%s' failed.\n", dbName);
    fprintf(stderr,"%s",PQerrorMessage(conn));
    exit_nicely(conn);
  }

  /* start a transaction block */
  res = PQexec(conn,"BEGIN"); 
  if (PQresultStatus(res) != PGRES_COMMAND_OK) {
    fprintf(stderr,"BEGIN command failed\n");
    PQclear(res);
    exit_nicely(conn);
  }
  /* should PQclear PGresult whenever it is no longer needed to avoid
     memory leaks */
  PQclear(res); 

  /* fetch instances from the pg_database, the system catalog of databases*/
  res = PQexec(conn,"DECLARE mycursor BINARY CURSOR FOR select * from test1");
  if (res == NULL || 
      PQresultStatus(res) != PGRES_COMMAND_OK) {
    fprintf(stderr,"DECLARE CURSOR command failed\n");
    if (res)
	PQclear(res);
    exit_nicely(conn);
  }
  PQclear(res);

  res = PQexec(conn,"FETCH ALL in mycursor");
  if (res == NULL ||
      PQresultStatus(res) != PGRES_TUPLES_OK) {
    fprintf(stderr,"FETCH ALL command didn't return tuples properly\n");
    if (res)
	PQclear(res);
    exit_nicely(conn);
  }
 
  i_fnum = PQfnumber(res,"i");
  d_fnum = PQfnumber(res,"d");
  p_fnum = PQfnumber(res,"p");
  
  for (i=0;i<3;i++) {
      printf("type[%d] = %d, size[%d] = %d\n",
	     i, PQftype(res,i), 
	     i, PQfsize(res,i));
  }
  for (i=0; i < PQntuples(res); i++) {
    int *ival; 
    float *dval;
    int plen;
    POLYGON* pval;
    /* we hard-wire this to the 3 fields we know about */
    ival =  (int*)PQgetvalue(res,i,i_fnum);
    dval =  (float*)PQgetvalue(res,i,d_fnum);
    plen = PQgetlength(res,i,p_fnum);

    /* plen doesn't include the length field so need to increment by VARHDSZ*/
    pval = (POLYGON*) malloc(plen + VARHDRSZ); 
    pval->size = plen;
    memmove((char*)&pval->npts, PQgetvalue(res,i,p_fnum), plen);
    printf("tuple %d: got\n", i);
    printf(" i = (%d bytes) %d,\n",
	   PQgetlength(res,i,i_fnum), *ival);
    printf(" d = (%d bytes) %f,\n",
	   PQgetlength(res,i,d_fnum), *dval);
    printf(" p = (%d bytes) %d points \tboundbox = (hi=%f/%f, lo = %f,%f)\n",
	   PQgetlength(res,i,d_fnum),
	   pval->npts,
	   pval->boundbox.xh,
	   pval->boundbox.yh,
	   pval->boundbox.xl,
	   pval->boundbox.yl);
  }

  PQclear(res);
  
  /* close the portal */
  res = PQexec(conn, "CLOSE mycursor");
  PQclear(res);

  /* end the transaction */
  res = PQexec(conn, "END");
  PQclear(res);

  /* close the connection to the database and cleanup */
  PQfinish(conn);

}