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The following page has been changed by AmirYoussefi:
---++++ 1. I'm using PigStorage to parse my input files. Can I make it use
control characters as delimiters?
A. Yes. Examples: PigStorage('\u0001') for Ctrl+A or '\u007C' for this
---++++2. Can I do a numerical comparison while filtering?
A. Yes, you can choose between numerical and string comparison. For numerical
comparison use the operators =, <>, < etc. and for string comparisons use eq,
---++++3. How do I make my jobs run on multiple machines?
A. Use the PARALLEL clause. For example =C = JOIN A by url, B by url PARALLEL
---++++4. Does Pig support NULLs?
A. Pig currently has no support for NULL values but it is on the roadmap.
---++++5. Does pig support regular expressions?
A. Pig does support regular expression matching via =matches= keyward. Tt uses
java.util.regexp matches which means your pattern has to match the entire
string (ie if your string is "hi fred" and you want to find "fred" you have to
give a pattern of ".*fred" not "fred").
---++++6. How to prevent failure if some records don't have the needed number
You can filter away those records by including the following in your Pig
A = load 'foo' using PigStorage('\t');
B = FILTER A BY ARITY(*) < 5;
This code would drop all the records that has less than 5 columns.
---++++7. Is there any difference between == and eq for numeric comparisons?
For equality, there is no difference while you stay in integers. However 11.0
and 11 will be equal with == but not with eq.
---++++8. Is there an easy way for me to figure out how many rows exists in a
dataset from its alias?
You can run the following set of commands:
a = load 'bla' ... ;
b = group a all;
c = foreach b generate COUNT(a.$0);
This is equivalent to select count(*) in SQL.
---++++9. Does Pig allow grouping on expressions
Currently, Pig only allows to group on data fields rather than expressions.
Allowing grouping on expressions is on our road map. Stay tuned!