marko-sisovic-db commented on code in PR #57564:
URL: https://github.com/apache/spark/pull/57564#discussion_r3682586122


##########
connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/V2JDBCTest.scala:
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@@ -1362,6 +1362,27 @@ private[v2] trait V2JDBCTest
     }
   }
 
+  test("fractional to integral cast pushed down truncates toward zero like 
Spark") {
+    val tbl = s"$catalogName.integral_cast"
+    withTable(tbl) {
+      // label is a string so the result type is the same across dialects (a 
numeric column
+      // comes back as BigDecimal on some engines such as Oracle).
+      sql(s"CREATE TABLE $tbl (double_col DOUBLE, decimal_col DECIMAL(10, 2), 
label VARCHAR(8))")
+      sql(s"INSERT INTO $tbl VALUES (1.5, 1.5, 'a'), (2.5, 2.5, 'b'), (-1.5, 
-1.5, 'c')")
+
+      // Spark truncates toward zero, so 1.5, 2.5 and -1.5 become 1, 2 and -1. 
A database that
+      // rounds half away from zero would return 2, 3 and -2 instead.
+      Seq("double_col", "decimal_col").foreach { col =>
+        val projected = sql(s"SELECT CAST($col AS INT) FROM $tbl ORDER BY 
$col")
+        assert(projected.collect().map(_.getInt(0)) === Array(-1, 1, 2))

Review Comment:
   Great point guys, I realized this in parallel after running the tests 
locally. The test now exercises three paths: it keeps projections (to catch 
potential future regressions) and it adds aggregate and filter cases, to test 
that pushdown gives correct results.



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