Geografic-Information-System/db/drivers/postgres/select.c

#include <stdlib.h>
#include <grass/dbmi.h>
#include <grass/gis.h>
#include "globals.h"
#include "proto.h"

int db__driver_open_select_cursor(dbString * sel, dbCursor * dbc, int mode)
{
    PGresult *res;
    cursor *c;
    dbTable *table;
    char *str;

    init_error();

    /* Set datetime style */
    res = PQexec(pg_conn, "SET DATESTYLE TO ISO");

    if (!res || PQresultStatus(res) != PGRES_COMMAND_OK) {
	append_error("Cannot set DATESTYLE\n");
	report_error();
	PQclear(res);
	return DB_FAILED;
    }

    PQclear(res);

    /* allocate cursor */
    c = alloc_cursor();
    if (c == NULL)
	return DB_FAILED;

    db_set_cursor_mode(dbc, mode);
    db_set_cursor_type_readonly(dbc);

    /* \ must be escaped, see explanation in db_driver_execute_immediate() */
    str = G_str_replace(db_get_string(sel), "\\", "\\\\");
    G_debug(3, "Escaped SQL: %s", str);

    c->res = PQexec(pg_conn, str);

    if (!c->res || PQresultStatus(c->res) != PGRES_TUPLES_OK) {
	append_error("Cannot select: \n");
	append_error(db_get_string(sel));
	append_error("\n");
	append_error(PQerrorMessage(pg_conn));
	report_error();
	PQclear(c->res);
	if (str)
	    G_free(str);
	return DB_FAILED;
    }

    if (str)
	G_free(str);

    if (describe_table(c->res, &table, c) == DB_FAILED) {
	append_error("Cannot describe table\n");
	report_error();
	PQclear(res);
	return DB_FAILED;
    }

    c->nrows = PQntuples(c->res);
    c->row = -1;

    /* record table with dbCursor */
    db_set_cursor_table(dbc, table);

    /* set dbCursor's token for my cursor */
    db_set_cursor_token(dbc, c->token);

    return DB_OK;
}