Calculating the averages for each KEY in a Pairwise (K,V) RDD in Spark with Python

Now a much better way to do this is to use the rdd.aggregateByKey() method. Because this method is so poorly documented in the Apache Spark with Python documentation — and is why I wrote this Q&A — until recently I had been using the above code sequence. But again, it’s less efficient, so avoid doing … Read more

What are aggregates and trivial types/PODs, and how/why are they special?

How to read: This article is rather long. If you want to know about both aggregates and PODs (Plain Old Data) take time and read it. If you are interested just in aggregates, read only the first part. If you are interested only in PODs then you must first read the definition, implications, and examples … Read more

AggregateException C# example

You need to call Handle on the inner exceptions. From MSDN’s documentation on Handle: Each invocation of the predicate returns true or false to indicate whether the Exception was handled. After all invocations, if any exceptions went unhandled, all unhandled exceptions will be put into a new AggregateException which will be thrown. Otherwise, the Handle … Read more

Repository Pattern: how to Lazy Load? or, Should I split this Aggregate?

Am I misinterpreting the intent of the Repository pattern? I’m going to say “yeah”, but know that me and every person I’ve worked with has asked the same thing for the same reason… “You’re not thinking 4th dimensionally, Marty”. Let’s simplify it a little and stick with constructors instead of Create methods first: Editor e … Read more

SELECT list is not in GROUP BY clause and contains nonaggregated column [duplicate]

As @Brian Riley already said you should either remove 1 column in your select select countrylanguage.language ,sum(country.population*countrylanguage.percentage/100) from countrylanguage join country on countrylanguage.countrycode = country.code group by countrylanguage.language order by sum(country.population*countrylanguage.percentage) desc ; or add it to your grouping select countrylanguage.language, country.code, sum(country.population*countrylanguage.percentage/100) from countrylanguage join country on countrylanguage.countrycode = country.code group by countrylanguage.language, country.code … Read more

SQL Server “cannot perform an aggregate function on an expression containing an aggregate or a subquery”, but Sybase can

One option is to put the subquery in a LEFT JOIN: select sum ( t.graduates ) – t1.summedGraduates from table as t left join ( select sum ( graduates ) summedGraduates, id from table where group_code not in (‘total’, ‘others’ ) group by id ) t1 on = where t.group_code=”total” group by t1.summedGraduates … Read more