[SPARK-52262][SQL] swap order of withConnection and classifyException in loadTable

### What changes were proposed in this pull request?

Swap order of `withConnection` and `classifyException` in `loadTable` since connection errors were swallowed with `FAILED_JDBC.TABLE_EXISTS`

### Why are the changes needed?

To not have misleading error message.

### Does this PR introduce _any_ user-facing change?

User would not see wrong wrapped error.

### How was this patch tested?

Added a unit test and used debugger locally.

### Was this patch authored or co-authored using generative AI tooling?

No

Closes #50986 from alekjarmov/remove-wrap-wrong-error.

Lead-authored-by: alekjarmov <[email protected]>
Co-authored-by: Alek Jarmov <[email protected]>
Co-authored-by: Alek Jarmov <[email protected]>
Signed-off-by: Wenchen Fan <[email protected]>

Author: 2 people

connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/V2JDBCTest.scala

@@ -1118,4 +1118,19 @@ private[v2] trait V2JDBCTest extends SharedSparkSession with DockerIntegrationFu
       testBinaryLiteral("<=>", greaterThanBinary, 0)
     }
   }
+
+  test("SPARK-52262: FAILED_JDBC.TABLE_EXISTS not thrown on connection error") {
+    val invalidTableName = s"$catalogName.invalid"
+    val originalUrl = spark.conf.get(s"spark.sql.catalog.$catalogName.url")
+    val invalidUrl = originalUrl.replace("localhost", "nonexistenthost")
+      .replace("127.0.0.1", "1.2.3.4")
+
+    withSQLConf(s"spark.sql.catalog.$catalogName.url" -> invalidUrl) {
+      // Ideally we would catch SQLException, but analyzer wraps it
+      val e = intercept[AnalysisException] {
+        sql(s"SELECT * FROM $invalidTableName")
+      }
+      assert(e.getCondition !== "FAILED_JDBC.TABLE_EXISTS")
+    }
+  }
 }

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/jdbc/JDBCTableCatalog.scala

@@ -94,15 +94,15 @@ class JDBCTableCatalog extends TableCatalog
     checkNamespace(ident.namespace())
     val writeOptions = new JdbcOptionsInWrite(
       options.parameters + (JDBCOptions.JDBC_TABLE_NAME -> getTableName(ident)))
-    JdbcUtils.classifyException(
-      condition = "FAILED_JDBC.TABLE_EXISTS",
-      messageParameters = Map(
-        "url" -> options.getRedactUrl(),
-        "tableName" -> toSQLId(ident)),
-      dialect,
-      description = s"Failed table existence check: $ident",
-      isRuntime = false) {
-      JdbcUtils.withConnection(options)(JdbcUtils.tableExists(_, writeOptions))
+    JdbcUtils.withConnection(options) {
+      JdbcUtils.classifyException(
+        condition = "FAILED_JDBC.TABLE_EXISTS",
+        messageParameters = Map(
+          "url" -> options.getRedactUrl(),
+          "tableName" -> toSQLId(ident)),
+        dialect,
+        description = s"Failed table existence check: $ident",
+        isRuntime = false)(JdbcUtils.tableExists(_, writeOptions))
     }
   }