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From srowen <...@git.apache.org>
Subject [GitHub] spark pull request #14502: [SPARK-16909][Spark Core] - Streaming for postgre...
Date Fri, 05 Aug 2016 07:06:35 GMT
Github user srowen commented on a diff in the pull request:

    https://github.com/apache/spark/pull/14502#discussion_r73650348
  
    --- Diff: core/src/main/scala/org/apache/spark/rdd/JdbcRDD.scala ---
    @@ -79,12 +79,18 @@ class JdbcRDD[T: ClassTag](
         val conn = getConnection()
         val stmt = conn.prepareStatement(sql, ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY)
     
    -    // setFetchSize(Integer.MIN_VALUE) is a mysql driver specific way to force streaming
results,
    -    // rather than pulling entire resultset into memory.
    -    // see http://dev.mysql.com/doc/refman/5.0/en/connector-j-reference-implementation-notes.html
    -    if (conn.getMetaData.getURL.matches("jdbc:mysql:.*")) {
    +    val url = conn.getMetaData.getURL
    +    if (url.matches("jdbc:mysql:.*")) {
    +      // setFetchSize(Integer.MIN_VALUE) is a mysql driver specific way to force streaming
results,
    +      // rather than pulling entire resultset into memory.
    +      // see http://dev.mysql.com/doc/refman/5.0/en/connector-j-reference-implementation-notes.html
    +
           stmt.setFetchSize(Integer.MIN_VALUE)
           logInfo("statement fetch size set to: " + stmt.getFetchSize + " to force MySQL
streaming ")
    +    } else if (url.matches("jdbc:postgresql:*")) {
    --- End diff --
    
    The regex is wrong, as it matches 0 or more : at the end. Actually, why don't we just
use startsWith in both cases? 
    
    Seems reasonable even if 10 is arbitrary. Is that low? but then again mysql above is asked
to retrieve row by row, and I'm not actually sure that's a good idea. I wonder if we should
dispense with this and just set it to something moderate like 1000 for all drivers? CC @koeninger

    
    Can you update the MySQL link above while you're here to https://dev.mysql.com/doc/connector-j/5.1/en/connector-j-reference-implementation-notes.html
as the existing one doesn't work.


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