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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