Установка
1
Установите libchdb
Установите библиотеку chDB в вашей системе:
curl -sL https://lib.chdb.io | bash
2
Подключите заголовочный файл
Подключите заголовочный файл chDB в проект:
#include <chdb.h>
3
Скомпилируйте и слинкуйте библиотеку
Скомпилируйте приложение и слинкуйте его с chDB:
# Компиляция C
gcc -o myapp myapp.c -lchdb
# Компиляция C++
g++ -o myapp myapp.cpp -lchdb
Примеры на C
Простое подключение и запросы
#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;
}
Потоковые запросы
#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;
}
Работа с различными форматами данных
#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;
}
Пример на 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;
}
Рекомендации по обработке ошибок
#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;
}
Репозиторий GitHub
- Основной репозиторий: chdb-io/chdb
- Проблемы и поддержка: Сообщайте о проблемах в репозитории GitHub
- Документация по C API: Документация по привязкам