chDB pour C et C++ | ClickHouse Docs

chDB fournit une API C/C++ native pour intégrer directement les fonctionnalités de ClickHouse à vos applications. L’API prend en charge aussi bien les requêtes simples que des fonctionnalités avancées comme les connexions persistantes et les résultats de requêtes en streaming.

Installation

Installer libchdb

Installez la bibliothèque chDB sur votre système :

curl -sL https://lib.chdb.io | bash

Inclure l’en-tête

Incluez l’en-tête chDB dans votre projet :

#include <chdb.h>

Lier la bibliothèque

Compilez et liez votre application avec chDB :

# Compilation C
gcc -o myapp myapp.c -lchdb

# Compilation C++  
g++ -o myapp myapp.cpp -lchdb

Exemples en C

Connexion simple et requêtes

#include <stdio.h>
#include <chdb.h>

int main() {
    // Create connection arguments
    char* args[] = {"chdb", "--path", "/tmp/chdb-data"};
    int argc = 3;
    
    // Connect to chDB
    chdb_connection* conn = chdb_connect(argc, args);
    if (!conn) {
        printf("Failed to connect to chDB\n");
        return 1;
    }
    
    // Execute a query
    chdb_result* result = chdb_query(*conn, "SELECT version()", "CSV");
    if (!result) {
        printf("Query execution failed\n");
        chdb_close_conn(conn);
        return 1;
    }
    
    // Check for errors
    const char* error = chdb_result_error(result);
    if (error) {
        printf("Query error: %s\n", error);
    } else {
        // Get result data
        char* data = chdb_result_buffer(result);
        size_t length = chdb_result_length(result);
        double elapsed = chdb_result_elapsed(result);
        uint64_t rows = chdb_result_rows_read(result);
        
        printf("Result: %.*s\n", (int)length, data);
        printf("Elapsed: %.3f seconds\n", elapsed);
        printf("Rows: %llu\n", rows);
    }
    
    // Cleanup
    chdb_destroy_query_result(result);
    chdb_close_conn(conn);
    return 0;
}

Requêtes en streaming

#include <stdio.h>
#include <chdb.h>

int main() {
    char* args[] = {"chdb", "--path", "/tmp/chdb-stream"};
    chdb_connection* conn = chdb_connect(3, args);
    
    if (!conn) {
        printf("Failed to connect\n");
        return 1;
    }
    
    // Start streaming query
    chdb_result* stream_result = chdb_stream_query(*conn, 
        "SELECT number FROM system.numbers LIMIT 1000000", "CSV");
    
    if (!stream_result) {
        printf("Failed to start streaming query\n");
        chdb_close_conn(conn);
        return 1;
    }
    
    uint64_t total_rows = 0;
    
    // Process chunks
    while (true) {
        chdb_result* chunk = chdb_stream_fetch_result(*conn, stream_result);
        if (!chunk) break;
        
        // Check if we have data in this chunk
        size_t chunk_length = chdb_result_length(chunk);
        if (chunk_length == 0) {
            chdb_destroy_query_result(chunk);
            break; // End of stream
        }
        
        uint64_t chunk_rows = chdb_result_rows_read(chunk);
        total_rows += chunk_rows;
        
        printf("Processed chunk: %llu rows, %zu bytes\n", chunk_rows, chunk_length);
        
        // Process the chunk data here
        // char* data = chdb_result_buffer(chunk);
        
        chdb_destroy_query_result(chunk);
        
        // Progress reporting
        if (total_rows % 100000 == 0) {
            printf("Progress: %llu rows processed\n", total_rows);
        }
    }
    
    printf("Streaming complete. Total rows: %llu\n", total_rows);
    
    // Cleanup streaming query
    chdb_destroy_query_result(stream_result);
    chdb_close_conn(conn);
    return 0;
}

Utiliser différents formats de données

#include <stdio.h>
#include <chdb.h>

int main() {
    char* args[] = {"chdb"};
    chdb_connection* conn = chdb_connect(1, args);
    
    const char* query = "SELECT number, toString(number) as str FROM system.numbers LIMIT 3";
    
    // CSV format
    chdb_result* csv_result = chdb_query(*conn, query, "CSV");
    printf("CSV Result:\n%.*s\n\n", 
           (int)chdb_result_length(csv_result), 
           chdb_result_buffer(csv_result));
    chdb_destroy_query_result(csv_result);
    
    // JSON format
    chdb_result* json_result = chdb_query(*conn, query, "JSON");
    printf("JSON Result:\n%.*s\n\n", 
           (int)chdb_result_length(json_result), 
           chdb_result_buffer(json_result));
    chdb_destroy_query_result(json_result);
    
    // Pretty format
    chdb_result* pretty_result = chdb_query(*conn, query, "Pretty");
    printf("Pretty Result:\n%.*s\n\n", 
           (int)chdb_result_length(pretty_result), 
           chdb_result_buffer(pretty_result));
    chdb_destroy_query_result(pretty_result);
    
    chdb_close_conn(conn);
    return 0;
}

Exemple en C++

#include <iostream>
#include <string>
#include <vector>
#include <chdb.h>

class ChDBConnection {
private:
    chdb_connection* conn;
    
public:
    ChDBConnection(const std::vector<std::string>& args) {
        // Convert string vector to char* array
        std::vector<char*> argv;
        for (const auto& arg : args) {
            argv.push_back(const_cast<char*>(arg.c_str()));
        }
        
        conn = chdb_connect(argv.size(), argv.data());
        if (!conn) {
            throw std::runtime_error("Failed to connect to chDB");
        }
    }
    
    ~ChDBConnection() {
        if (conn) {
            chdb_close_conn(conn);
        }
    }
    
    std::string query(const std::string& sql, const std::string& format = "CSV") {
        chdb_result* result = chdb_query(*conn, sql.c_str(), format.c_str());
        if (!result) {
            throw std::runtime_error("Query execution failed");
        }
        
        const char* error = chdb_result_error(result);
        if (error) {
            std::string error_msg(error);
            chdb_destroy_query_result(result);
            throw std::runtime_error("Query error: " + error_msg);
        }
        
        std::string data(chdb_result_buffer(result), chdb_result_length(result));
        
        // Get query statistics
        std::cout << "Query statistics:\n";
        std::cout << "  Elapsed: " << chdb_result_elapsed(result) << " seconds\n";
        std::cout << "  Rows read: " << chdb_result_rows_read(result) << "\n";
        std::cout << "  Bytes read: " << chdb_result_bytes_read(result) << "\n";
        
        chdb_destroy_query_result(result);
        return data;
    }
};

int main() {
    try {
        // Create connection
        ChDBConnection db({{"chdb", "--path", "/tmp/chdb-cpp"}});
        
        // Create and populate table
        db.query("CREATE TABLE test (id UInt32, value String) ENGINE = MergeTree() ORDER BY id");
        db.query("INSERT INTO test VALUES (1, 'hello'), (2, 'world'), (3, 'chdb')");
        
        // Query with different formats
        std::cout << "CSV Results:\n" << db.query("SELECT * FROM test", "CSV") << "\n";
        std::cout << "JSON Results:\n" << db.query("SELECT * FROM test", "JSON") << "\n";
        
        // Aggregation query
        std::cout << "Count: " << db.query("SELECT COUNT(*) FROM test") << "\n";
        
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
        return 1;
    }
    
    return 0;
}

Bonnes pratiques de gestion des erreurs

#include <stdio.h>
#include <chdb.h>

int safe_query_example() {
    chdb_connection* conn = NULL;
    chdb_result* result = NULL;
    int return_code = 0;
    
    // Create connection
    char* args[] = {"chdb"};
    conn = chdb_connect(1, args);
    if (!conn) {
        printf("Failed to create connection\n");
        return 1;
    }
    
    // Execute query
    result = chdb_query(*conn, "SELECT invalid_syntax", "CSV");
    if (!result) {
        printf("Query execution failed\n");
        return_code = 1;
        goto cleanup;
    }
    
    // Check for query errors
    const char* error = chdb_result_error(result);
    if (error) {
        printf("Query error: %s\n", error);
        return_code = 1;
        goto cleanup;
    }
    
    // Process successful result
    printf("Result: %.*s\n", 
           (int)chdb_result_length(result), 
           chdb_result_buffer(result));
    
cleanup:
    if (result) chdb_destroy_query_result(result);
    if (conn) chdb_close_conn(conn);
    return return_code;
}

Dépôt GitHub

Dépôt principal : chdb-io/chdb
Problèmes et support : Signalez les problèmes dans le dépôt GitHub
Documentation de l’API C : Documentation des bindings