Github user CK50 commented on a diff in the pull request:
https://github.com/apache/spark/pull/10066#discussion_r46405509
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/jdbc/CassandraDialect.scala ---
@@ -0,0 +1,53 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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+ */
+
+package org.apache.spark.sql.jdbc
+
+import java.sql.Types
+
+import org.apache.spark.sql.types._
+
+
+private case object CassandraDialect extends JdbcDialect {
+
+ override def canHandle(url: String): Boolean =
+ url.startsWith("jdbc:datadirect:cassandra") ||
+ url.startsWith("jdbc:weblogic:cassandra")
+
+ override def getInsertStatement(table: String, rddSchema: StructType):
String = {
+ val sql = new StringBuilder(s"INSERT INTO $table ( ")
+ var fieldsLeft = rddSchema.fields.length
+ var i = 0
+ // Build list of column names
+ while (fieldsLeft > 0) {
+ sql.append(rddSchema.fields(i).name)
+ if (fieldsLeft > 1) sql.append(", ")
--- End diff --
Yes, this is exactly the problem encountered.
What if we drop the new Dialect and add a new signature on
DataFrameWriter instead (new columnMapping param):
def jdbc(url: String, table: String, connectionProperties: Properties,
columnMapping: Map<String,String>): Unit
The old signature then continues using the column-name-free INSERT
syntax, but for any advanced use-cases (or technologies, which do not
support column-name-free syntax) the new API can be used.
This ensures full backwards compatibility for all technologies
If this is the way to go, I'd better start a new PR?
My preference would still to keep the refactoring of moving generation
of INSERT statement into the Dialect (instead of in JDBCUtils). Does
this make sense?
On 02.12.2015 11:46, Sean Owen wrote:
>
> In
> sql/core/src/main/scala/org/apache/spark/sql/jdbc/CassandraDialect.scala
> <https://github.com/apache/spark/pull/10066#discussion_r46399876>:
>
> > +
> > +
> > +private case object CassandraDialect extends JdbcDialect {
> > +
> > + override def canHandle(url: String): Boolean =
> > + url.startsWith("jdbc:datadirect:cassandra") ||
> > + url.startsWith("jdbc:weblogic:cassandra")
> > +
> > + override def getInsertStatement(table: String, rddSchema:
StructType): String = {
> > + val sql = new StringBuilder(s"INSERT INTO $table ( ")
> > + var fieldsLeft = rddSchema.fields.length
> > + var i = 0
> > + // Build list of column names
> > + while (fieldsLeft > 0) {
> > + sql.append(rddSchema.fields(i).name)
> > + if (fieldsLeft > 1) sql.append(", ")
>
> You're just saying that inserting a DataFrame of m columns into a
> table of n > m columns doesn't work, right? Yes without column name
> mappings, I expect this to fail anytime m != n, for any database.
> Right now this assumes m = n implicitly.
>
> You're right that adding names requires a mapping from data frame
> column names to DB column names. Hm, I wonder if this needs an
> optional |Map| allowing for overrides.
>
> I don't think the regression tests cover all databases, no. I also
> don't think this can be specific to Oracle anyway.
>
> My workflow for squashing N of the last commits is:
>
> * |git rebase -i HEAD~N|
> * Change all but the first "pick" to "squash" in the editor and save
> * Edit the commit message down to just 1 logical message and save
> * |git push --force origin [your branch]|
>
> â
> Reply to this email directly or view it on GitHub
> <https://github.com/apache/spark/pull/10066/files#r46399876>.
>
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