Main Content

persist

Class: matlab.compiler.mlspark.RDD
Package: matlab.compiler.mlspark

Set the value of an RDD’s storage level to persist across operations after it is computed

Syntax

persist(obj,storageLevel)

Description

persist(obj,storageLevel) sets a persistent storage level specified by storageLevel in RDD object obj. The default storage level is MEMORY_ONLY. Use the persist method to assign a new storage level if obj does not have a storage level set. You can also use it to set a persistent storage level in memory across operations.

Input Arguments

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An input RDD, specified as an RDD object.

New storage level to be assigned, specified as a character vector enclosed in ''. Use storageLevel to assign a new storage level if the RDD does not have a storage level set. The default storage level is MEMORY_ONLY.

Storage LevelDescription
MEMORY_ONLY

Store the RDD in memory. If the RDD does not fit in memory, some partitions are not cached, and are recomputed each time they are needed.

DISK_ONLY

Store the RDD partitions on disk.

MEMORY_AND_DISK

Store the RDD in memory. If it does not fit in memory, then spill to disk.

MEMORY_ONLY_2

Store the RDD in memory, but replicate each partition in two cluster nodes.

DISK_ONLY_2

Store the RDD partitions on disk, but replicate each partition in two cluster nodes.

MEMORY_AND_DISK_2

Store the RDD in memory. If it does not fit in memory, then spill to disk. Replicate each partition in two cluster nodes.

OFF_HEAPStore RDD in serialized format. For more information, see the programming guide at https://spark.apache.org/

Data Types: char

Examples

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Use the persist method without any parameter to store an RDD in the memory of the executors across a cluster.

%% Connect to Spark
sparkProp = containers.Map({'spark.executor.cores'}, {'1'});
conf = matlab.compiler.mlspark.SparkConf('AppName','myApp', ...
                        'Master','local[1]','SparkProperties',sparkProp);
sc = matlab.compiler.mlspark.SparkContext(conf);

%% persist
myFile = sc.textFile('airlinesmall.csv');
myFile.persist();
myFile.unpersist();
Introduced in R2016b