Order by date time in pig script - apache-pig

Question

After pig 0.11.0, datetime basic variable type is introduced for processing. In my case i have to order by date time. I used this way
data = LOAD 'database_name.table_name' USING org.apache.hcatalog.pig.HCatLoader() AS (id:chararray,name:chararray,birth_date_time:chararray);
selected_data = FOREACH data GENERATE id, name,ToDate(birth_date_time,'yyyy-MM-dd HH:mm:ss') AS birth_date_time;
ordered_data = ORDER selected_data BY birth_date_time DESC;
DUMP ordered_data;
But i t doesn't work. throws this error
org.apache.pig.impl.logicalLayer.FrontendException: ERROR 1066: Unable
to open iterator for alias cba_ordered. Backend error : Unable to
recreate exception from backed error:
AttemptID:attempt_1452577118821_0005_m_000000_3 Info:Error:
org.joda.time.DateTime.compareTo(Lorg/joda/time/ReadableInstant;)I
at org.apache.pig.PigServer.openIterator(PigServer.java:872)
at org.apache.pig.tools.grunt.GruntParser.processDump(GruntParser.java:774)
at org.apache.pig.tools.pigscript.parser.PigScriptParser.parse(PigScriptParser.java:372)
at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:198)
at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:173)
at org.apache.pig.tools.grunt.Grunt.exec(Grunt.java:84)
at org.apache.pig.Main.run(Main.java:607)
at org.apache.pig.Main.main(Main.java:156)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.main(RunJar.java:212) Caused by: org.apache.pig.backend.executionengine.ExecException: ERROR 2997:
Unable to recreate exception from backed error:
AttemptID:attempt_1452577118821_0005_m_000000_3 Info:Error:
org.joda.time.DateTime.compareTo(Lorg/joda/time/ReadableInstant;)I
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.Launcher.getErrorMessages(Launcher.java:217)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.Launcher.getStats(Launcher.java:151)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher.launchPig(MapReduceLauncher.java:429)
at org.apache.pig.PigServer.launchPlan(PigServer.java:1324)
at org.apache.pig.PigServer.executeCompiledLogicalPlan(PigServer.java:1309)
at org.apache.pig.PigServer.storeEx(PigServer.java:980)
at org.apache.pig.PigServer.store(PigServer.java:944)
at org.apache.pig.PigServer.openIterator(PigServer.java:857)
... 12 more
How can we order by date_time field?

Answer 1

I will suggest you to use ToUnixTime(datetime) function to order date column.
Please check below and do like this.
data = LOAD 'database_name.table_name' USING org.apache.hcatalog.pig.HCatLoader() AS (id:chararray,name:chararray,birth_date_time:chararray);
selected_data = FOREACH data {
bdt = (datetime)ToDate(birth_date_time,'yyyy-MM-dd HH:mm:ss');
GENERATE id, name, bdt AS birth_date_time, ToUnixTime(bdt) AS birth_date_time_unix;
};
ordered_data = ORDER selected_data BY birth_date_time_unix DESC;
DUMP ordered_data;
Please let me know if it works.