set hive.merge.mapredfiles = true;
时间: 2024-05-20 21:16:28 浏览: 22
This command enables the merging of small Hadoop MapReduce files into larger files in Apache Hive. This can help improve query performance by reducing the number of small files that need to be read and processed. When this configuration parameter is set to true, Hive will merge the output files of each MapReduce task into a single file. The resulting files are typically larger, but fewer in number. However, it's important to note that setting this parameter to true may increase the time required to complete a MapReduce job because of the additional overhead required to merge the files.
相关问题
hive> set hive.cli.print.header=true;set hive.cli.print.current.db=true;set hive.cli.print.row.to.vertical=true;set mapred.output.encoding=UTF-8;set mapred.input.encoding=UTF-8;set hive.input.format=org.apache.hadoop.hive.ql.io.HiveInputFormat;set hive.exec.compress.output=false;set hive.exec.compress.intermediate=false;set hive.vectorized.execution.enabled=true;set hive.vectorized.execution.reduce.enabled=true;set hive.vectorized.execution.reduce.groupby.enabled=true; Query returned non-zero code: 1, cause: hive configuration hive.cli.print.row.to.vertical does not exists. hive (default)>
抱歉,之前提供的配置有误,可能是因为不同版本的Hive配置不同。以下是一组通用的配置,可以尝试在Hive中执行:
```
set hive.cli.print.header=true;
set hive.cli.print.current.db=true;
set hive.cli.print.row.to.vertical=false;
set mapred.output.encoding=UTF-8;
set mapred.input.encoding=UTF-8;
set hive.input.format=org.apache.hadoop.hive.ql.io.HiveInputFormat;
set hive.exec.compress.output=false;
set hive.exec.compress.intermediate=false;
set hive.vectorized.execution.enabled=true;
set hive.vectorized.execution.reduce.enabled=true;
set hive.groupby.skewindata=true;
```
这组配置可以将Hive的输出编码方式设置为UTF-8,并启用一些Hive的优化方式。如果还有其他问题,请告诉我。
SET ngmr.partition.automerge=true; SET ngmr.partition.mergesize=125;
这是两个Hive参数设置语句,用于优化Hive的MapReduce任务。
第一个参数 `ngmr.partition.automerge=true` 是用来开启自动合并小文件的功能,当Hive进行MapReduce任务时,产生大量小文件会导致效率低下,使用该参数可以自动将小文件合并成一个更大的文件,提高效率。
第二个参数 `ngmr.partition.mergesize=125` 是设置自动合并小文件的文件大小阈值,当小文件总大小达到该阈值时,会触发自动合并操作。该参数的值需要根据具体情况进行调整,以达到最佳效果。