From e03b95002d64176fff52cd2bc59da414fe7f1255 Mon Sep 17 00:00:00 2001
From: TJ Banghart <66929211+tjbanghart@users.noreply.github.com>
Date: Sun, 5 Feb 2023 22:36:53 -0800
Subject: [PATCH] Always check for aliases when deriving data types (#13)

---
 .../java/org/apache/calcite/sql/SqlDataTypeSpec.java  |  6 +++++-
 .../test/java/org/apache/calcite/test/UdtTest.java    | 11 +++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/org/apache/calcite/sql/SqlDataTypeSpec.java b/core/src/main/java/org/apache/calcite/sql/SqlDataTypeSpec.java
index 3433113119fe..50a8f82cd4fb 100644
--- a/core/src/main/java/org/apache/calcite/sql/SqlDataTypeSpec.java
+++ b/core/src/main/java/org/apache/calcite/sql/SqlDataTypeSpec.java
@@ -230,7 +230,11 @@ public RelDataType deriveType(SqlValidator validator) {
    */
   public RelDataType deriveType(SqlValidator validator, boolean nullable) {
     RelDataType type;
-    type = typeNameSpec.deriveType(validator);
+    // check if the type name is being used as an alias before calling `deriveType`
+    type = validator.getCatalogReader().getNamedType(typeNameSpec.getTypeName());
+    if (type == null) {
+      type = typeNameSpec.deriveType(validator);
+    }
 
     // Fix-up the nullability, default is false.
     final RelDataTypeFactory typeFactory = validator.getTypeFactory();
diff --git a/core/src/test/java/org/apache/calcite/test/UdtTest.java b/core/src/test/java/org/apache/calcite/test/UdtTest.java
index 970a40a0b785..e9930a3c68fb 100644
--- a/core/src/test/java/org/apache/calcite/test/UdtTest.java
+++ b/core/src/test/java/org/apache/calcite/test/UdtTest.java
@@ -29,6 +29,10 @@ private CalciteAssert.AssertThat withUdt() {
         + "     {\n"
         + "       name: 'foo',\n"
         + "       type: 'BIGINT'\n"
+        + "     },\n"
+        + "     {\n"
+        + "       name: 'TIMESTAMP',\n"
+        + "       type: 'TIMESTAMP_WITH_LOCAL_TIME_ZONE'\n"
         + "     }"
         + "   ],\n"
         + "   schemas: [\n"
@@ -71,6 +75,13 @@ private CalciteAssert.AssertThat withUdt() {
     withUdt().query(sql).returns("LD=1\n");
   }
 
+  @Test void testAliasOnBasicType() {
+    final String sql = "select CAST(\"date\" AS TIMESTAMP) as ts "
+        + "from (VALUES ROW(DATE '2020-12-25', 'SameName')) AS \"t\" (\"date\", \"desc\")";
+    withUdt().query(sql).typeIs("[TS TIMESTAMP_WITH_LOCAL_TIME_ZONE NOT NULL]");
+  }
+
+
   /** Test case for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-3045">[CALCITE-3045]
    * NullPointerException when casting null literal to composite user defined type</a>. */