Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/8676#discussion_r39230872
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcUtils.scala
---
@@ -42,10 +42,13 @@ object JdbcUtils extends Logging {
/**
* Returns true if the table already exists in the JDBC database.
*/
- def tableExists(conn: Connection, table: String): Boolean = {
+ def tableExists(conn: Connection, url: String, table: String): Boolean =
{
+ val dialect = JdbcDialects.get(url)
+
// Somewhat hacky, but there isn't a good way to identify whether a
table exists for all
- // SQL database systems, considering "table" could also include the
database name.
- Try(conn.prepareStatement(s"SELECT 1 FROM $table LIMIT
1").executeQuery().next()).isSuccess
+ // SQL database systems using JDBC meta data calls, considering
"table" could also include
+ // the database name. Query used to find table exists can be overriden
by the dialects.
+
Try(conn.prepareStatement(dialect.getTableExistsQuery(table)).executeQuery().next()).isSuccess
--- End diff --
will next still return success if the query is where 1 = 0? there is no
result isn't there?
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