在 PostgreSQL 数据库中 in 查询 本身是没有硬性限制的；但是在 jdbc 驱动中，对其进行限制了；
1. jdbc 4.20.0 版本之前
/*
代码位置：
org.postgresql.core.PGStream#sendInteger2
*/
/**
* Sends a 2-byte integer (short) to the back end.
*
* @param val the integer to be sent
* @throws IOException if an I/O error occurs or {@code val} cannot be encoded in 2 bytes
*/
public void sendInteger2(int val) throws IOException {
if (val < Short.MIN_VALUE || val > Short.MAX_VALUE) {
throw new IOException("Tried to send an out-of-range integer as a 2-byte value: " + val);
}
int2Buf[0] = (byte) (val >>> 8);
int2Buf[1] = (byte) val;
pgOutput.write(int2Buf);
}
其中 Short.MAX_VALUE 为 32767个；故 in 查询 限制为 32767 个；
2. jdbc 4.20.0 及以前版本
/*
代码位置：
org.postgresql.core.PGStream#sendInteger2
*/
/**
* Sends a 2-byte integer (short) to the back end.
*
* @param val the integer to be sent
* @throws IOException if an I/O error occurs or {@code val} cannot be encoded in 2 bytes
*/
public void sendInteger2(int val) throws IOException {
if (val < 0 || val > 65535) {
throw new IllegalArgumentException("Tried to send an out-of-range integer as a 2-byte unsigned int value: " + val);
}
int2Buf[0] = (byte) (val >>> 8);
int2Buf[1] = (byte) val;
pgOutput.write(int2Buf);
}
作者修复这个缺陷，将限制调整为无符号 Short 最大长度；
3. 参考链接
转向：