From 735770ffb7d3d950a51dfbb7170026f316f64fb0 Mon Sep 17 00:00:00 2001
From: Marcin Rusek <marcin.rusek@starburstdata.com>
Date: Wed, 23 Aug 2023 17:34:13 +0200
Subject: [PATCH] Coerce varchar(0) to varchar(1) for Hive table

---
 .../io/trino/plugin/hive/HiveMetadata.java    | 10 ++++++
 .../plugin/hive/BaseHiveConnectorTest.java    | 35 +++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/plugin/trino-hive/src/main/java/io/trino/plugin/hive/HiveMetadata.java b/plugin/trino-hive/src/main/java/io/trino/plugin/hive/HiveMetadata.java
index 966b4ff7c8b38..287afee216412 100644
--- a/plugin/trino-hive/src/main/java/io/trino/plugin/hive/HiveMetadata.java
+++ b/plugin/trino-hive/src/main/java/io/trino/plugin/hive/HiveMetadata.java
@@ -124,6 +124,7 @@
 import io.trino.spi.type.TimestampType;
 import io.trino.spi.type.Type;
 import io.trino.spi.type.TypeManager;
+import io.trino.spi.type.VarcharType;
 import org.apache.avro.Schema;
 import org.apache.avro.SchemaParseException;
 import org.apache.hadoop.fs.Path;
@@ -3414,6 +3415,15 @@ public Optional<ConnectorTableLayout> getNewTableLayout(ConnectorSession session
                 multipleWritersPerPartitionSupported));
     }
 
+    @Override
+    public Optional<Type> getSupportedType(ConnectorSession session, Type type)
+    {
+        if (type instanceof VarcharType varcharType && !varcharType.isUnbounded() && varcharType.getBoundedLength() == 0) {
+            return Optional.of(VarcharType.createVarcharType(1));
+        }
+        return Optional.empty();
+    }
+
     @Override
     public Optional<ConnectorTableLayout> getLayoutForTableExecute(ConnectorSession session, ConnectorTableExecuteHandle executeHandle)
     {
diff --git a/plugin/trino-hive/src/test/java/io/trino/plugin/hive/BaseHiveConnectorTest.java b/plugin/trino-hive/src/test/java/io/trino/plugin/hive/BaseHiveConnectorTest.java
index 20749bd40fbde..3d705556a7297 100644
--- a/plugin/trino-hive/src/test/java/io/trino/plugin/hive/BaseHiveConnectorTest.java
+++ b/plugin/trino-hive/src/test/java/io/trino/plugin/hive/BaseHiveConnectorTest.java
@@ -7987,6 +7987,41 @@ public void testWriteInvalidPrecisionTimestamp()
                 "\\QIncorrect timestamp precision for timestamp(3); the configured precision is " + HiveTimestampPrecision.MICROSECONDS + "; column name: ts");
     }
 
+    @Test
+    public void testCoercingVarchar0ToVarchar1()
+    {
+        try (TestTable testTable = new TestTable(
+                getQueryRunner()::execute,
+                "test_coercion_create_table_varchar",
+                "(var_column_0 varchar(0), var_column_1 varchar(1), var_column_10 varchar(10))")) {
+            assertEquals(getColumnType(testTable.getName(), "var_column_0"), "varchar(1)");
+            assertEquals(getColumnType(testTable.getName(), "var_column_1"), "varchar(1)");
+            assertEquals(getColumnType(testTable.getName(), "var_column_10"), "varchar(10)");
+        }
+    }
+
+    @Test
+    public void testCoercingVarchar0ToVarchar1WithCTAS()
+    {
+        try (TestTable testTable = new TestTable(
+                getQueryRunner()::execute,
+                "test_coercion_ctas_varchar",
+                "AS SELECT '' AS var_column")) {
+            assertEquals(getColumnType(testTable.getName(), "var_column"), "varchar(1)");
+        }
+    }
+
+    @Test
+    public void testCoercingVarchar0ToVarchar1WithCTASNoData()
+    {
+        try (TestTable testTable = new TestTable(
+                getQueryRunner()::execute,
+                "test_coercion_ctas_nd_varchar",
+                "AS SELECT '' AS var_column WITH NO DATA")) {
+            assertEquals(getColumnType(testTable.getName(), "var_column"), "varchar(1)");
+        }
+    }
+
     @Test
     public void testOptimize()
     {