apache spark - DataFrame join optimization - Stack Overflow
Broadcast Hash Joins (similar to map side join or map-side combine in Mapreduce) : In SparkSQL you can see the type of join being performed by calling queryExecution.executedPlan. As with core Spark, if one of the tables is much smaller than the other you may want a broadcast hash join. You can hint to Spark SQL that a given DF should be broadcast for join by calling method broadcast on the DataFr
What is the difference between HashingTF and CountVectorizer in Spark?
As per the Spark 2.1.0 documentation, Both HashingTF and CountVectorizer can be used to generate the term frequency vectors. HashingTF HashingTF is a Transformer which takes sets of terms and converts those sets into fixed-length feature vectors. In text processing, a “set of terms” might be a bag of words. HashingTF utilizes the hashing trick. A raw feature is mapped into an index (term) by apply
How do I iterate RDD's in apache spark (scala)
You call various methods on the RDD that accept functions as parameters. // set up an example -- an RDD of arrays val sparkConf = new SparkConf().setMaster("local").setAppName("Example") val sc = new SparkContext(sparkConf) val testData = Array(Array(1,2,3), Array(4,5,6,7,8)) val testRDD = sc.parallelize(testData, 2) // Print the RDD of arrays. testRDD.collect().foreach(a => println(a.size)) // Us
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Applying a Window function to calculate differences in pySpark
