小编Dim*_*maf的帖子

我需要在 Postgres 9.4 中执行以下事务：

BEGIN TRANSACTION;
    TRUNCATE TestTable;
    COPY TestTable FROM '/DATAforTestTable' DELIMITER ',' CSV;
END TRANSACTION;

用户必须在执行事务时对 TestTable 中的“旧”数据具有读取权限，而无需等待事务结束。是否可以？或者我必须通过处理和重命名表来完成？

有人可以解释一下，为什么goroutine有无限for循环并且循环select内部，循环中的代码只运行一次？

package main

import (
    "time"
)

func f1(quit chan bool){
    go func() {
        for {
            println("f1 is working...")
            time.Sleep(1 * time.Second)

            select{
            case <-quit:
            println("stopping f1")
            break
            }
        }   
    }()
}

func main() {
    quit := make(chan bool)
    f1(quit)
    time.Sleep(4 * time.Second)
}

输出：

f1 is working...
Program exited.

但是，如果“选择”被注释掉：

package main

import (
    "time"
)

func f1(quit chan bool){
    go func() {
        for {
            println("f1 is working...")
            time.Sleep(1 * time.Second)

            //select{
            //case <-quit:
            //println("stopping …

将数据恢复到 Cassandra 集群（1 个节点）后，出现错误：

ERROR [CompactionExecutor:7] 2016-05-09 08:05:38,621 CassandraDaemon.java:185 - Exception in thread Thread[CompactionExecutor:7,1,main]
java.lang.UnsupportedOperationException: Bloom filter size is > 16GB, reduce the bloom_filter_fp_chance
        at org.apache.cassandra.utils.obs.OffHeapBitSet.<init>(OffHeapBitSet.java:40) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.utils.FilterFactory.createFilter(FilterFactory.java:85) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.utils.FilterFactory.getFilter(FilterFactory.java:78) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.io.sstable.format.big.BigTableWriter$IndexWriter.<init>(BigTableWriter.java:470) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.io.sstable.format.big.BigTableWriter.<init>(BigTableWriter.java:86) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.io.sstable.format.big.BigFormat$WriterFactory.open(BigFormat.java:107) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.io.sstable.format.SSTableWriter.create(SSTableWriter.java:84) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.db.compaction.writers.DefaultCompactionWriter.<init>(DefaultCompactionWriter.java:52) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.db.compaction.CompactionTask.getCompactionAwareWriter(CompactionTask.java:237) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.db.compaction.CompactionTask.runMayThrow(CompactionTask.java:174) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.db.compaction.CompactionTask.executeInternal(CompactionTask.java:74) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.db.compaction.AbstractCompactionTask.execute(AbstractCompactionTask.java:59) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at org.apache.cassandra.db.compaction.CompactionManager$BackgroundCompactionCandidate.run(CompactionManager.java:256) ~[apache-cassandra-2.2.5.jar:2.2.5]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[na:1.8.0_71]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_71]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) ~[na:1.8.0_71]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_71]
        at java.lang.Thread.run(Thread.java:745) …