CLEAR_HDFS_CACHES

Clears the configuration information copied from HDFS and any cached connections.

This function affects reads using the hdfs scheme in the following ways:

  • This function flushes information loaded from configuration files copied from Hadoop (such as core-site.xml). These files are found on the path set by the HadoopConfDir configuration parameter.
  • This function flushes information about which NameNode is active in a High Availability (HA) Hadoop cluster. Therefore, the first request to Hadoop after calling this function is slower than expected.

Vertica maintains a cache of open connections to NameNodes to reduce latency. This function flushes that cache.

Syntax

CLEAR_HDFS_CACHES (  )

Privileges

Superuser

Example

The following example clears the Hadoop configuration information:

=> SELECT CLEAR_HDFS_CACHES();
 CLEAR_HDFS_CACHES
--------------
 Cleared
(1 row)

See Also

Apache Hadoop Parameters