LOAD Operator

Loading data from ElasticSearch

Before checking the specific syntax, let's take a look on how to setup your environment to load needed plugins.

Setup

To load data directly from ElasticSearch you need to download the elasticsearch-hadoop plugin. You have different ways to make it work, for a quick setup you can do the following.

In order to make it work, you need to put the jar file elasticsearch-hadoop-<version>.jar in a folder of the node where you have the pig server installed. In my case - quite common googling around - I also needed to add commons-httpclient-<version>.jar inside that folder.

Then you can run pig in shell mode (called grunt) simply typing pig on the console. Then you have to load those two jars in the following way:

REGISTER /path/to/jars/commons-httpclient-<version>.jar;
REGISTER /path/to/jars/elasticsearch-hadoop-<version>.jar;

Now you are ready to write some code.

Example

Let's check the syntax to load data from a complex case.

DATA = LOAD 'my_index/log' USING org.elasticsearch.hadoop.pig.EsStorage(
'es.nodes=https://server1:port1,https://server2:port2,https://server3:port3',
'es.query=?q=*',
'es.net.ssl=true',
'es.net.http.auth.user=user',
'es.net.http.auth.pass=pass',
'es.net.ssl.keystore.type=JKS',
'es.net.ssl.truststore.location=file:///path/to/truststore.jks',
'es.net.ssl.truststore.pass=pass');

This is the complete example, now let's analyze it step by step.

  • es.nodes holds the list of the nodes of your ElasticSearch cluster. You have to specify your nodes as a comma separated list, with the associated port.
  • es.query holds the query that will be submitted to ElasticSearch in order to fetch data. You can also put a query in DSL format, but be careful that only the match part of the query will be considered! If you try to limit the number of fields through the query DSL it won't work: in order to achieve that you need to use the es.read.source.filter parameter. example of a query DSL: 'es.query = { "query":{ "match_all":{} } }'
  • es.net.ssl=true is self explanatory, you need also to give the login credentials to ElasticSearch with es.net.http.auth.user and es.net.http.auth.pass.
  • es.net.ssl.keystore.type if you need a truststore, you can select here the type. In the es.net.ssl.truststore.location parameter you set the location of the file, be careful to add file:// prefix, and in the es.net.ssl.truststore.pass parameter you set the password of the truststore file.

Some useful settings

  • es.read.source.filter=field1,field2,field3 allows you to fetch only the specified fields from ElasticSearch (in this example three).
  • es.output.json=true allows you to fetch data in a key-value format (JSON). Setting to false will return data in CSV format (default).

Loading Stock market data

Let us assume the following stock market data stored in HDFS. It is a CSV file with fields: Symbol, Date, Open, High, Close & Volume.

ABT,20160106,42.310001,42.98,42.209999,42.560001,5906000
BAC,20160201,14.05,14.09,13.8,13.96,105739400
CAS,20160129,1.9,1.97,1.83,1.84,34500
DCA,20160129,3.46,3.54,3.46,3.51,84600
ECL,20160114,103.480003,105.400002,102.480003,104.82,1485000
FAF,20160201,34.040001,34.82,33.939999,34.639999,1222600
TYL,20160201,156.070007,159.550003,155.690002,158.259995,177100
UTL,20160201,38.610001,39.889999,38.57,39.27,119500
VTR,20160128,54.09,54.73,53.549999,53.790001,2441300
WWE,20160201,17.629999,18,17.27,17.799999,734100
XRX,20160104,10.41,10.43,10.13,10.3,9122600
YUM,20160104,71.32,72.25,70.639999,72.209999,3466300
ZTR,20160104,12.1,12.14,11.98,12.11,60200

Example 1 A simple LOAD statement for the above data would look like:

stocks = load '/user/pig/stock.txt' using PigStorage(',') as 
             (sym:chararray, date:int, open:float, high:float, low:float, 
              close:float, vol:int);


2016-10-05
2017-05-04
apache-pig Pedia
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