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Josh Rosen commented on SPARK-17618: ------------------------------------ Yep, the problem is that {{Coalesce}} advertises that it accepts Unsafe rows but misdeclares its row output format as being regular rows. Comparing an UnsafeRow to any other row type for equality always returns false (its {{equals()}} implementation is compatible with Java universal equality, so it doesn't throw when performing a comparison against a different type). As a result, the Except compares safe and unsafe rows, causing the comparisons to be incorrect and leading to the wrong answer that you saw here. I'm marking this as a blocker for 1.6.3 and am working on a fix which will fix this issue. > Dataframe except returns incorrect results when combined with coalesce > ---------------------------------------------------------------------- > > Key: SPARK-17618 > URL: https://issues.apache.org/jira/browse/SPARK-17618 > Project: Spark > Issue Type: Bug > Components: SQL > Affects Versions: 1.6.1, 1.6.2 > Reporter: Graeme Edwards > Priority: Blocker > Labels: correctness > > We were getting incorrect results from the DataFrame except method - all rows > were being returned instead of the ones that intersected. Calling subtract on > the underlying RDD returned the correct result. > We tracked it down to the use of coalesce - the following is the simplest > example case we created that reproduces the issue: > {code} > val schema = new StructType().add("test", types.IntegerType ) > val t1 = sql.createDataFrame(sql.sparkContext.parallelize(1 to 100).map(i=> > Row(i)), schema) > val t2 = sql.createDataFrame(sql.sparkContext.parallelize(5 to 10).map(i=> > Row(i)), schema) > val t3 = t1.join(t2, t1.col("test").equalTo(t2.col("test")), "leftsemi") > println("Count using normal except = " + t1.except(t3).count()) > println("Count using coalesce = " + > t1.coalesce(8).except(t3.coalesce(8)).count()) > {code} > We should get the same result from both uses of except, but the one using > coalesce returns 100 instead of 94. -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org