Question

我正在尝试将多行传递给测试表，而我无法理解它在libpq中的完成情况。

我发现了我认为需要复制数据的命令，但没有任何关于如何使用它们的示例。 https://www.postgresql.org/docs/8.3/static/libpq-copy.html

这是我提出的代码，但是我在PQputCopyEnd函数中遇到了分段错误。我很失落，所以任何帮助都会很棒。

/*
 * testlibpq.c
 *
 *      Test the C version of libpq, the PostgreSQL frontend library.
 */
#include <stdio.h>
#include <string>
#include <stdlib.h>
#include <postgresql/libpq-fe.h>

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

int main(int argc, char **argv)
{
    const char *conninfo, *errmsg;
    PGconn     *conn;
    PGresult   *res;

    //std::string buffer = "key1\tcol11\tcol12\nley2\tcol21\tcol22";
    std::string buffer = "key1\tcol11\tcol12";


    if (argc > 1)
        conninfo = argv[1];
    else
        conninfo = "dbname=postgres host=129.24.26.136 user=postgres password=postgresUNM";

    /* Make a connection to the database */
    conn = PQconnectdb(conninfo);

    /* Check to see that the backend connection was successfully made */
    if (PQstatus(conn) != CONNECTION_OK)
    {
        fprintf(stderr, "Connection to database failed: %s",
                PQerrorMessage(conn));
        exit_nicely(conn);
    }

    //do stuff here
    res = PQexec(conn, "COPY cplusplustest from STDIN");
    int a = PQputCopyData(conn, buffer.c_str(), buffer.length());

    res = PQexec(conn, "COMMIT");

    int b = PQputCopyEnd(conn, errmsg);

    if (errmsg == NULL)
    {
        printf("worked.\n");
    }

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

    return 0;
}

Answer 1

postgres-8.3很老了;请考虑更新的版本
b = PQputCopyEnd(conn, errmsg);的errmsg参数必须设置为NULL（它是libpq的输入，表示客户端已中止副本）（the manual仍然相当模糊，我同意。
我删除了C ++。
COMMIT应该在 CopyEnd之后。

/* * testlibpq.c * * Test the C version of libpq, the PostgreSQL frontend library. */ #include <stdio.h> #include <string.h> // <<-- #include <stdlib.h> // #include <postgresql/libpq-fe.h> // <<-- #include <libpq-fe.h> static void exit_nicely(PGconn *conn) { PQfinish(conn); exit(1); } int main(int argc, char **argv) { const char *conninfo, *errmsg; PGconn *conn; PGresult *res; int a,b; // <<-- char buffer[] = "key1\tcol11\tcol12"; if (argc > 1) conninfo = argv[1]; else conninfo = "dbname=test host=/tmp/ user=postgres"; /* Make a connection to the database */ conn = PQconnectdb(conninfo); /* Check to see that the backend connection was successfully made */ if (PQstatus(conn) != CONNECTION_OK) { fprintf(stderr, "Connection to database failed: %s" , PQerrorMessage(conn)); exit_nicely(conn); } //do stuff here errmsg = NULL; // << HERE res = PQexec(conn, "COPY cplusplustest(key1,col11,col12) from STDIN;"); a = PQputCopyData(conn, buffer, strlen(buffer) ); b = PQputCopyEnd(conn, errmsg); printf("Res=%p a=%d,b=%d\n", res, a, b); if (errmsg ) printf("Failed:%s\n", errmsg); else printf("worked.\n"); res = PQexec(conn, "COMMIT;"); // <<-- HERE /* close the connection to the database and cleanup */ PQfinish(conn); return 0; }

libpq如何传递批量数据

1 个答案: