Cassandra 卡桑德拉有睡眠cql查询吗？

我正在寻找PostgreSQL中的

SELECT pg_sleep（t）

，或t-SQL中的

waitfor

。这是否存在于Cassandra cql中？

没有任何内置函数。使用UDF以及白名单和黑名单很难做到这一点：

白名单模式

"com/datastax/driver/core/",
"com/google/common/reflect/TypeToken",
"java/io/IOException.class",
"java/io/Serializable.class",
"java/lang/",
"java/math/",
"java/net/InetAddress.class",
"java/net/Inet4Address.class",
"java/net/Inet6Address.class",
"java/net/UnknownHostException.class", // req'd by InetAddress
"java/net/NetworkInterface.class", // req'd by InetAddress
"java/net/SocketException.class", // req'd by InetAddress
"java/nio/Buffer.class",
"java/nio/ByteBuffer.class",
"java/text/",
"java/time/",
"java/util/",
"org/apache/cassandra/cql3/functions/JavaUDF.class",
"org/apache/cassandra/cql3/functions/UDFContext.class",
"org/apache/cassandra/exceptions/",
"org/apache/cassandra/transport/ProtocolVersion.class"

"com/datastax/driver/core/Cluster.class",
"com/datastax/driver/core/Metrics.class",
"com/datastax/driver/core/NettyOptions.class",
"com/datastax/driver/core/Session.class",
"com/datastax/driver/core/Statement.class",
"com/datastax/driver/core/TimestampGenerator.class", // indirectly covers ServerSideTimestampGenerator + ThreadLocalMonotonicTimestampGenerator
"java/lang/Compiler.class",
"java/lang/InheritableThreadLocal.class",
"java/lang/Package.class",
"java/lang/Process.class",
"java/lang/ProcessBuilder.class",
"java/lang/ProcessEnvironment.class",
"java/lang/ProcessImpl.class",
"java/lang/Runnable.class",
"java/lang/Runtime.class",
"java/lang/Shutdown.class",
"java/lang/Thread.class",
"java/lang/ThreadGroup.class",
"java/lang/ThreadLocal.class",
"java/lang/instrument/",
"java/lang/invoke/",
"java/lang/management/",
"java/lang/ref/",
"java/lang/reflect/",
"java/util/ServiceLoader.class",
"java/util/Timer.class",
"java/util/concurrent/",
"java/util/function/",
"java/util/jar/",
"java/util/logging/",
"java/util/prefs/",
"java/util/spi/",
"java/util/stream/",
"java/util/zip/"

黑名单模式

"com/datastax/driver/core/",
"com/google/common/reflect/TypeToken",
"java/io/IOException.class",
"java/io/Serializable.class",
"java/lang/",
"java/math/",
"java/net/InetAddress.class",
"java/net/Inet4Address.class",
"java/net/Inet6Address.class",
"java/net/UnknownHostException.class", // req'd by InetAddress
"java/net/NetworkInterface.class", // req'd by InetAddress
"java/net/SocketException.class", // req'd by InetAddress
"java/nio/Buffer.class",
"java/nio/ByteBuffer.class",
"java/text/",
"java/time/",
"java/util/",
"org/apache/cassandra/cql3/functions/JavaUDF.class",
"org/apache/cassandra/cql3/functions/UDFContext.class",
"org/apache/cassandra/exceptions/",
"org/apache/cassandra/transport/ProtocolVersion.class"

"com/datastax/driver/core/Cluster.class",
"com/datastax/driver/core/Metrics.class",
"com/datastax/driver/core/NettyOptions.class",
"com/datastax/driver/core/Session.class",
"com/datastax/driver/core/Statement.class",
"com/datastax/driver/core/TimestampGenerator.class", // indirectly covers ServerSideTimestampGenerator + ThreadLocalMonotonicTimestampGenerator
"java/lang/Compiler.class",
"java/lang/InheritableThreadLocal.class",
"java/lang/Package.class",
"java/lang/Process.class",
"java/lang/ProcessBuilder.class",
"java/lang/ProcessEnvironment.class",
"java/lang/ProcessImpl.class",
"java/lang/Runnable.class",
"java/lang/Runtime.class",
"java/lang/Shutdown.class",
"java/lang/Thread.class",
"java/lang/ThreadGroup.class",
"java/lang/ThreadLocal.class",
"java/lang/instrument/",
"java/lang/invoke/",
"java/lang/management/",
"java/lang/ref/",
"java/lang/reflect/",
"java/util/ServiceLoader.class",
"java/util/Timer.class",
"java/util/concurrent/",
"java/util/function/",
"java/util/jar/",
"java/util/logging/",
"java/util/prefs/",
"java/util/spi/",
"java/util/stream/",
"java/util/zip/"

如果你真的需要它并且愿意做一些可怕的事情，比如：

CREATE OR REPLACE FUNCTION sleep (time int)
  CALLED ON NULL INPUT RETURNS int LANGUAGE java AS 
  '
  long start = System.currentTimeMillis();
  while (System.currentTimeMillis() < start + time);
  return time;
  ';

创建或替换函数睡眠（time int）
在NULL输入上调用返回int语言java作为
'
长启动=System.currentTimeMillis（）；
while（System.currentTimeMillis（）<开始+时间）；
返回时间；
';

---

但这是一个非常可怕的想法，因为它是一个紧密的循环。也许你可以在循环中引入暂停，但从我的粗略观察来看，黑名单的限制性很大。

称这种循环确实很可怕。有没有办法使用比java更大白名单的另一种语言？