Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/15263#discussion_r80845381
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcRelationProvider.scala
---
@@ -50,67 +51,48 @@ class JdbcRelationProvider extends
CreatableRelationProvider
JDBCRelation(jdbcOptions.url, jdbcOptions.table, parts,
properties)(sqlContext.sparkSession)
}
- /*
- * The following structure applies to this code:
- * | tableExists | !tableExists
-
*------------------------------------------------------------------------------------
- * Ignore | BaseRelation | CreateTable, saveTable,
BaseRelation
- * ErrorIfExists | ERROR | CreateTable, saveTable,
BaseRelation
- * Overwrite* | (DropTable, CreateTable,) | CreateTable, saveTable,
BaseRelation
- * | saveTable, BaseRelation |
- * Append | saveTable, BaseRelation | CreateTable, saveTable,
BaseRelation
- *
- * *Overwrite & tableExists with truncate, will not drop & create, but
instead truncate
- */
override def createRelation(
sqlContext: SQLContext,
mode: SaveMode,
parameters: Map[String, String],
- data: DataFrame): BaseRelation = {
- val jdbcOptions = new JDBCOptions(parameters)
- val url = jdbcOptions.url
- val table = jdbcOptions.table
-
+ df: DataFrame): BaseRelation = {
+ val options = new JDBCOptions(parameters)
+ val url = options.url
+ val table = options.table
+ val createTableOptions = options.createTableOptions
+ val isTruncate = options.isTruncate
val props = new Properties()
props.putAll(parameters.asJava)
- val conn = JdbcUtils.createConnectionFactory(url, props)()
+ val conn = JdbcUtils.createConnectionFactory(url, props)()
try {
val tableExists = JdbcUtils.tableExists(conn, url, table)
+ if (tableExists) {
+ mode match {
+ case SaveMode.Overwrite =>
+ if (isTruncate &&
isCascadingTruncateTable(url).contains(false)) {
+ // In this case, we should truncate table and then load.
+ truncateTable(conn, table)
+ saveTable(df, url, table, props)
+ } else {
+ // Otherwise, do not truncate but just drop.
--- End diff --
This comment looks weird. In RDBMS, users might do `drop and recreate` a
table, instead of truncating it. Thus, please change it to
`// Otherwise, do not truncate but just drop and recreate`
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