Github user koeninger commented on a diff in the pull request:
https://github.com/apache/spark/pull/14502#discussion_r73681837
--- 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 --
As I recall, the issue there is that otherwise the mysql driver will
attempt to materialize the entire result set in memory at once, regardless
of how big it is.
On Aug 5, 2016 2:07 AM, "Sean Owen" <[email protected]> wrote:
> In core/src/main/scala/org/apache/spark/rdd/JdbcRDD.scala
> <https://github.com/apache/spark/pull/14502#discussion_r73650348>:
>
> > stmt.setFetchSize(Integer.MIN_VALUE)
> > logInfo("statement fetch size set to: " + stmt.getFetchSize + "
to force MySQL streaming ")
> > + } else if (url.matches("jdbc:postgresql:*")) {
>
> 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
> <https://github.com/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.
>
> â
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