From 794829c57f12b2b303c717f3364929a285634993 Mon Sep 17 00:00:00 2001
From: Max Gekk <max.gekk@gmail.com>
Date: Sun, 14 Mar 2021 11:29:54 +0900
Subject: [PATCH] [SPARK-34727][SQL] Fix discrepancy in casting float to
 timestamp

### What changes were proposed in this pull request?
In non-ANSI mode, casting float to timestamp has different implementation for codegen on and off.

Codegen on:
1. Multiply float input by MICROS_PER_SECOND
2. Cast resulting float value to long

Codegen off:
1. CAST float input to double input
2. Multiply double input by MICROS_PER_SECOND
3. Cast resulting double value to long

In the PR, I propose to align to non-codegen code, and cast input float to double in codegen.

### Why are the changes needed?
This fixes the issue which is demonstrated by the code:
```sql
spark-sql> CREATE TEMP VIEW v1 AS SELECT 16777215.0f AS f;
spark-sql> SELECT * FROM v1;
1.6777215E7
spark-sql> SELECT CAST(f AS TIMESTAMP) FROM v1;
1970-07-14 07:20:15
spark-sql> CACHE TABLE v1;
spark-sql> SELECT * FROM v1;
1.6777215E7
spark-sql> SELECT CAST(f AS TIMESTAMP) FROM v1;
1970-07-14 07:20:14.951424
```
The result from the cached view **1970-07-14 07:20:14.951424** is different from un-cached view **1970-07-14 07:20:15**.

### Does this PR introduce _any_ user-facing change?
Yes. After the changes, the example above outputs the same timestamp for the cached view:
```sql
spark-sql> CACHE TABLE v1;
spark-sql> SELECT * FROM v1;
1.6777215E7
spark-sql> SELECT CAST(f AS TIMESTAMP) FROM v1;
1970-07-14 07:20:15
```

### How was this patch tested?
By running new test:
```
$ build/sbt "test:testOnly *CastSuite"
```

Closes #31819 from MaxGekk/fix-float-to-timestamp.

Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
---
 .../org/apache/spark/sql/catalyst/expressions/Cast.scala      | 2 +-
 .../org/apache/spark/sql/catalyst/expressions/CastSuite.scala | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
index 72bd9ca4d3d1c..80cd6d6c86312 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
@@ -1301,7 +1301,7 @@ abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression wit
           if (Float.isNaN($c) || Float.isInfinite($c)) {
             $evNull = true;
           } else {
-            $evPrim = (long)($c * $MICROS_PER_SECOND);
+            $evPrim = (long)((double)$c * $MICROS_PER_SECOND);
           }
         """
   }
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
index dae5304653743..d435aa0eb4c05 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
@@ -1507,6 +1507,10 @@ class CastSuite extends CastSuiteBase {
   test("Cast from double II") {
     checkEvaluation(cast(cast(1.toDouble, TimestampType), DoubleType), 1.toDouble)
   }
+
+  test("SPARK-34727: cast from float II") {
+    checkCast(16777215.0f, java.time.Instant.ofEpochSecond(16777215))
+  }
 }
 
 /**