Apache发布存储在PostGIS数据库栅格数据的数据库连接池版本（效率好像没有提升）

直接上代码：

#ifndef CDATABASE_CONNECTION_POOL_H
#define CDATABASE_CONNECTION_POOL_H

#include <libpq-fe.h>
#include <windows.h>  // 使用 Windows 线程库

// Initialize the database connection pool
void initConnectionPool(int poolSize, const char* conninfo);

// Get a connection from the pool
PGconn* getConnectionFromPool();

// Return a connection to the pool
void releaseConnectionToPool(PGconn* conn);

#endif // CDATABASE_CONNECTION_POOL_H

#include "CDatabaseConnectionPool.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

typedef struct {
    PGconn** connections;
    int poolSize;
    int currentSize;
    CRITICAL_SECTION lock;  // 使用 Windows 的临界区对象来替代 pthread_mutex_t
} ConnectionPool;

static ConnectionPool pool;

void initConnectionPool(int poolSize, const char* conninfo) {
    pool.connections = (PGconn**)malloc(poolSize * sizeof(PGconn*));
    if (!pool.connections) {
        fprintf(stderr, "Failed to allocate memory for connection pool.\n");
        return;
    }
    pool.poolSize = poolSize;
    pool.currentSize = 0;
    InitializeCriticalSection(&pool.lock);  // 初始化临界区对象

    for (int i = 0; i < poolSize; i++) {
        PGconn* conn = PQconnectdb(conninfo);
        if (PQstatus(conn) == CONNECTION_BAD) {
            fprintf(stderr, "Connection to database failed: %s", PQerrorMessage(conn));
            PQfinish(conn);
        }
        else {
            pool.connections[pool.currentSize++] = conn;
            fprintf(stderr, "Connection %d created and added to pool.\n", i);
        }
    }
}

PGconn* getConnectionFromPool() {
    PGconn* conn = NULL;
    EnterCriticalSection(&pool.lock);  // 进入临界区

    if (pool.currentSize > 0) {
        conn = pool.connections[--pool.currentSize];
        fprintf(stderr, "Connection retrieved from pool. Remaining connections: %d\n", pool.currentSize);
    }
    else {
        fprintf(stderr, "No connections available in pool.\n");
    }