Postgres 上的 C 语言环境和 Posix 语言环境有什么区别

### Postgres 上的 C 语言环境与 Posix 语言环境的区别

c
#include "postgres.h"
#include "fmgr.h"
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(sample_function);
Datum
sample_function(PG_FUNCTION_ARGS)
{
    // C语言函数的具体实现
    // ...
    PG_RETURN_NULL();
}

c
#include 
#include 
#include 
#define NUM_THREADS 5
void *thread_function(void *arg)
{
    int thread_id = *((int *)arg);
    printf("Hello from thread %d%
", thread_id);
    pthread_exit(NULL);
}
int main()
{
    pthread_t threads[NUM_THREADS];
    int thread_args[NUM_THREADS];
    int i;
    for (i = 0; i < NUM_THREADS; i++)
    {
        thread_args[i] = i;
        pthread_create(&threads[i], NULL, thread_function, (void *)&thread_args[i]);
    }
    for (i = 0; i < NUM_THREADS; i++)
    {
        pthread_join(threads[i], NULL);
    }
    printf("All threads have completed.%
");
    return 0;
}