Thank you for your response Zhen, I am using some vendor specific JDBC driver JAR file (honestly I dont know where it came from). It’s api is NOT like JdbcRDD, instead, more like jdbc from DataFrameReader https://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.sql.DataFrameReader
So I ask two questions now: 1. Will running a query using JdbcRDD prove better than bringing an entire table as DataFrame? I am later on, converting back to RDDs. 2. I lack of some proper criteria to decide a proper column for distributon. My table has more than 400 columns. Saif From: shenyan zhen [mailto:shenya...@gmail.com] Sent: Tuesday, July 28, 2015 4:16 PM To: Ellafi, Saif A. Cc: user@spark.apache.org Subject: Re: Fighting against performance: JDBC RDD badly distributed Hi Saif, Are you using JdbcRDD directly from Spark? If yes, then the poor distribution could be due to the bound key you used. See the JdbcRDD Scala doc at https://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.rdd.JdbcRDD: sql the text of the query. The query must contain two ? placeholders for parameters used to partition the results. E.g. "select title, author from books where ? <= id and id <= ?" lowerBound the minimum value of the first placeholder upperBound the maximum value of the second placeholder The lower and upper bounds are inclusive. numPartitions the number of partitions. Given a lowerBound of 1, an upperBound of 20, and a numPartitions of 2, the query would be executed twice, once with (1, 10) and once with (11, 20) Shenyan On Tue, Jul 28, 2015 at 2:41 PM, <saif.a.ell...@wellsfargo.com<mailto:saif.a.ell...@wellsfargo.com>> wrote: Hi all, I am experimenting and learning performance on big tasks locally, with a 32 cores node and more than 64GB of Ram, data is loaded from a database through JDBC driver, and launching heavy computations against it. I am presented with two questions: 1. My RDD is poorly distributed. I am partitioning into 32 pieces, but first 31 pieces are extremely lightweight compared to piece 32 15/07/28 13:37:48 INFO Executor: Finished task 30.0 in stage 0.0 (TID 30). 1419 bytes result sent to driver 15/07/28 13:37:48 INFO TaskSetManager: Starting task 31.0 in stage 0.0 (TID 31, localhost, PROCESS_LOCAL, 1539 bytes) 15/07/28 13:37:48 INFO Executor: Running task 31.0 in stage 0.0 (TID 31) 15/07/28 13:37:48 INFO TaskSetManager: Finished task 30.0 in stage 0.0 (TID 30) in 2798 ms on localhost (31/32) 15/07/28 13:37:48 INFO CacheManager: Partition rdd_2_31 not found, computing it ...All pieces take 3 seconds while last one takes around 15 minutes to compute... Is there anything I can do about this? preferrably without reshufling, i.e. in the DataFrameReader JDBC options (lowerBound, upperBound, partition column) 2. After long time of processing, sometimes I get OOMs, I fail to find a how-to for fallback and give retries to already persisted data to avoid time. Thanks, Saif
