libpqxx v12 - 将向量值动态绑定到准备好的语句（替代调用）

我想使用准备好的语句一次将数千行插入到我的 postgres 数据库中。要插入的数据存储在结构向量中。

通过阅读以下问题的答案如何在 Postgresql for C++ 中准备语句和绑定参数我想我找到了方法。

不幸的是，我使用的当前版本的 libpqxx 不支持pqxx::准备::调用不再，我无法在文档/互联网中找到任何替代方案。

我出于我的目的尝试的代码如下：

//pqxx header
#include "pqxx/connection.hxx" 
#include "pqxx/transaction.hxx"
#include "pqxx/nontransaction.hxx"
#include "pqxx/compiler-public.hxx"
#include "pqxx/result.hxx"
#include "pqxx/prepared_statement.hxx"
#include "pqxx/transaction_base.hxx"
#include "pqxx/internal/statement_parameters.hxx"

...
int main(){

    struct testData {
       string uuid;
       float rndNo;
       string timestamp;
    };

    vector<testData> dataBuffer;
    testData dbdata;

    string queryStr;
    const char* query;

    stringstream connStream;
    stringstream queryStream;

    string DB_NAME = "dbname";
    string DB_USER = "postgres";
    string DB_PASSWORD = "password";
    string DB_HOSTADDR = "127.0.0.1";
    string DB_PORT = "1234";
    string DB_SCHEMA = "test_schema";
    string tableName = "test_table";

    //Create Random data 

    for (int i = 0; i < 100000; i++) {

        dbdata.uuid = "fe2b22ba-6ce7-4bbc-8226-d7696fe7a047";
        dbdata.rndNo = i / 3.123;
        dbdata.timestamp = systemDateTimeSQLFormat(0);

        dataBuffer.push_back(dbdata);
    }

    stringstream connStream;
    connStream << "dbname = " << DB_NAME << " user = " << DB_USER << " password = " << DB_PASSWORD << " hostaddr = " << DB_HOSTADDR << " port = " << DB_PORT;

    connection dbConn(connStream.str());
    if (dbConn.is_open()) {
        cout << "Opened database successfully: " << dbConn.dbname() << endl;
    }
    else {
        cout << "Can't open database" << endl;
        return;
    }


    pqxx::nontransaction W(dbConn);
    std::string m_insertCommand = "INSERT INTO test_schema.test_table (column1, column2, column3) VALUES";

    int buffSize = dataBuffer.size();

    for (size_t i = 0; i < buffSize; i++)
    {
        unsigned int countOf$ = i * 3;
        for (unsigned int i = 0; i < 3; ++i)
        {
            if (i == 0)
            {
                m_insertCommand += "(";
            }
            else
            {
                m_insertCommand += ", ";
            }
            m_insertCommand += "$";
            std::stringstream ss;
            ss << countOf$ + i + 1;
            m_insertCommand += ss.str();
        }
        if (i < buffSize - 1)
            m_insertCommand += ") ,";
    }
    m_insertCommand += ")";


    //FOLLOWING CODE NOT POSSIBLE WITH libpqxx v12

    dbConn.prepare("insert_into_db", m_insertCommand);
    pqxx::prepare::invocation = W.exec_prepared("insert_into_db");  //prepare doesn't have a member "invocation"


    for (size_t i = 0; i < buffSize; i++)
    {
        inv(dataBuffer.at(i).rndNo)(dataBuffer.at(i).timestamp)(dataBuffer.at(i).uuid); //inv not defined
    }

    inv.exec();

return 1;
}

pqxx::prepare::make_dynamic_params可能会解决你的问题。它解决了我的问题。使用这种方式：

for (size_t i = 0; i < buffSize; ++i)
{
    auto element = dataBuffer.at(i);
    vector<string> vect;
    vect.reserve(3);
    vect.push_back(pqxx::to_string(element.rndNo));
    vect.push_back(element.timestamp);
    vect.push_back(element.uuid);

    work.exec_params(m_insertCommand, pqxx::prepare::make_dynamic_params(vect));
}

从版本来看7.6.0不推荐使用dynamic_params。可以使用 params 代替。这是新的解决方案：

for (size_t i = 0; i < buffSize; ++i) 
{
    auto element = dataBuffer.at(i);
    pqxx::params;
    params.reserve(4);
    params.append(pqxx::to_string(element.rndNo));
    params.append(element.timestamp);
    params.append(element.uuid);
    params.append(); // For example insert null variable

    work.exec_params(m_insertCommand, params);
}