libpqxx v12 - 将向量值动态绑定到准备好的语句(替代调用) [英] libpqxx v12 - dynamically bind vector-values to prepared statement (alternative to invocation)

问题描述

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 How to在 Postgresql for C++ 中准备语句和绑定参数 我以为我找到了方法.

不幸的是，我使用的当前版本的 libpqxx 不再支持 pqxx::prepare::invocation，我无法在文档/互联网中找到任何替代方案.>

我为我的目的尝试的代码如下:

//pqxx 头#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(){结构测试数据{字符串 uuid;浮点数；字符串时间戳；};向量数据缓冲区；测试数据数据库数据；字符串 queryStr;const char* 查询；stringstream connStream;字符串流查询流；字符串 DB_NAME = "dbname";字符串 DB_USER = "postgres";字符串 DB_PASSWORD = 密码"；字符串 DB_HOSTADDR = "127.0.0.1";字符串 DB_PORT = "1234";字符串 DB_SCHEMA = "test_schema";string tableName = "test_table";//创建随机数据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<<"用户 = "<<DB_USER<<"密码 = "<<DB_PASSWORD ＜＜"主机地址 = "<<DB_HOSTADDR ＜＜"端口 = "<<DB_PORT;连接 dbConn(connStream.str());如果(dbConn.is_open()){cout<<"成功打开数据库:"<<dbConn.dbname() <<结束;}别的 {cout<<无法打开数据库"<<结束;返回;}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){如果(我== 0){m_insertCommand += "(";}别的{m_insertCommand += ", ";}m_insertCommand += "$";std::stringstream ss;ss<

解决方案

pqxx::prepare::make_dynamic_params 可能会解决您的问题.它解决了我的问题.使用这种方式:

for (size_t i = 0; i 向量;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));}

I would like to use prepared statements to insert thousands of rows at once into my postgres database. The data to insert is stored in a vector of structs.

By reading the answers to How to prepare statements and bind parameters in Postgresql for C++ I thought I found the way how to do it.

Unfortunately, the current version of libpqxx I am using doesn't support pqxx::prepare::invocation anymore and I wasn't able to find any alternative in the docs/internet.

The code I tried out for my purpose is the following:

//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;
}

解决方案

pqxx::prepare::make_dynamic_params will probably solve your problem. It's solved my problem. Use this way:

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));
}

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