Allow char to varchar coercion for hive tables

docs/src/main/sphinx/connector/hive.md

@@ -611,7 +611,7 @@ type conversions.
   - `BOOLEAN`, `TINYINT`, `SMALLINT`, `INTEGER`, `BIGINT`, `REAL`, `DOUBLE`, `TIMESTAMP`, `DATE`, `CHAR` as well as
     narrowing conversions for `VARCHAR`
 * - `CHAR`
-  - narrowing conversions for `CHAR`
+  - `VARCHAR`, narrowing conversions for `CHAR`
 * - `TINYINT`
   - `VARCHAR`, `SMALLINT`, `INTEGER`, `BIGINT`, `DOUBLE`, `DECIMAL`
 * - `SMALLINT`

plugin/trino-hive/src/main/java/io/trino/plugin/hive/coercions/CharToVarcharCoercer.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.trino.plugin.hive.coercions;
+
+import io.trino.spi.block.Block;
+import io.trino.spi.block.BlockBuilder;
+import io.trino.spi.type.CharType;
+import io.trino.spi.type.VarcharType;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static io.trino.spi.type.Varchars.truncateToLength;
+
+public class CharToVarcharCoercer
+        extends TypeCoercer<CharType, VarcharType>
+{
+    public CharToVarcharCoercer(CharType fromType, VarcharType toType)
+    {
+        super(fromType, toType);
+        checkArgument(toType.getBoundedLength() < fromType.getLength(), "Coercer to a wider varchar type should not be required");
+    }
+
+    @Override
+    protected void applyCoercedValue(BlockBuilder blockBuilder, Block block, int position)
+    {
+        toType.writeSlice(blockBuilder, truncateToLength(fromType.getSlice(block, position), toType.getBoundedLength()));
+    }
+}

plugin/trino-hive/src/main/java/io/trino/plugin/hive/coercions/CoercionUtils.java

@@ -148,6 +148,12 @@ public static Type createTypeFromCoercer(TypeManager typeManager, HiveType fromH
             }
             return Optional.empty();
         }
+        if (fromType instanceof CharType fromCharType && toType instanceof VarcharType toVarcharType) {
+            if (!toVarcharType.isUnbounded() && toVarcharType.getBoundedLength() < fromCharType.getLength()) {
+                return Optional.of(new CharToVarcharCoercer(fromCharType, toVarcharType));
+            }
+            return Optional.empty();
+        }
         if (fromHiveType.equals(HIVE_BYTE)) {
             if (toHiveType.equals(HIVE_SHORT) || toHiveType.equals(HIVE_INT) || toHiveType.equals(HIVE_LONG)) {
                 return Optional.of(new IntegerNumberUpscaleCoercer<>(fromType, toType));

plugin/trino-hive/src/main/java/io/trino/plugin/hive/util/HiveCoercionPolicy.java

@@ -74,7 +74,8 @@ private boolean canCoerce(HiveType fromHiveType, HiveType toHiveType, HiveTimest
                     toHiveType.equals(HIVE_TIMESTAMP);
         }
         if (fromType instanceof CharType) {
-            return toType instanceof CharType;
+            return toType instanceof CharType ||
+                    toType instanceof VarcharType;
         }
         if (toType instanceof VarcharType) {
             return fromHiveType.equals(HIVE_BOOLEAN) ||

plugin/trino-hive/src/test/java/io/trino/plugin/hive/coercions/TestCharToVarcharCoercer.java

@@ -0,0 +1,54 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.trino.plugin.hive.coercions;
+
+import io.trino.plugin.hive.coercions.CoercionUtils.CoercionContext;
+import io.trino.spi.block.Block;
+import io.trino.spi.type.Type;
+import org.junit.jupiter.api.Test;
+
+import static io.airlift.slice.Slices.utf8Slice;
+import static io.trino.plugin.hive.HiveTimestampPrecision.DEFAULT_PRECISION;
+import static io.trino.plugin.hive.HiveType.toHiveType;
+import static io.trino.plugin.hive.coercions.CoercionUtils.createCoercer;
+import static io.trino.spi.predicate.Utils.blockToNativeValue;
+import static io.trino.spi.predicate.Utils.nativeValueToBlock;
+import static io.trino.spi.type.CharType.createCharType;
+import static io.trino.spi.type.VarcharType.createVarcharType;
+import static io.trino.type.InternalTypeManager.TESTING_TYPE_MANAGER;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TestCharToVarcharCoercer
+{
+    @Test
+    public void testCharToSmallerVarcharCoercions()
+    {
+        assertCharToVarcharCoercion("a", createCharType(3), "a", createVarcharType(2));
+        assertCharToVarcharCoercion(" a", createCharType(3), " a", createVarcharType(2));
+        assertCharToVarcharCoercion(" aa", createCharType(4), " a", createVarcharType(2));
+        assertCharToVarcharCoercion("a", createCharType(3), "a", createVarcharType(2));
+        assertCharToVarcharCoercion("\uD83D\uDCB0\uD83D\uDCB0\uD83D\uDCB0", createCharType(3), "\uD83D\uDCB0", createVarcharType(1));
+        assertCharToVarcharCoercion("\uD83D\uDCB0\uD83D\uDCB0", createCharType(7), "\uD83D\uDCB0\uD83D\uDCB0", createVarcharType(6));
+        assertCharToVarcharCoercion("\uD83D\uDCB0", createCharType(3), "\uD83D\uDCB0", createVarcharType(1));
+        assertCharToVarcharCoercion("\uD83D\uDCB0 \uD83D\uDCB0", createCharType(7), "\uD83D\uDCB0 \uD83D\uDCB0", createVarcharType(6));
+    }
+
+    private static void assertCharToVarcharCoercion(String actualValue, Type fromType, String expectedValue, Type toType)
+    {
+        Block coercedBlock = createCoercer(TESTING_TYPE_MANAGER, toHiveType(fromType), toHiveType(toType), new CoercionContext(DEFAULT_PRECISION, false)).orElseThrow()
+                .apply(nativeValueToBlock(fromType, utf8Slice(actualValue)));
+        assertThat(blockToNativeValue(toType, coercedBlock))
+                .isEqualTo(utf8Slice(expectedValue));
+    }
+}

testing/trino-product-tests/src/main/java/io/trino/tests/product/hive/BaseTestHiveCoercion.java

@@ -183,6 +183,9 @@ protected void doTestHiveCoercion(HiveTableDefinition tableDefinition)
                 "date_to_bounded_varchar",
                 "char_to_bigger_char",
                 "char_to_smaller_char",
+                "char_to_string",
+                "char_to_bigger_varchar",
+                "char_to_smaller_varchar",
                 "string_to_char",
                 "varchar_to_bigger_char",
                 "varchar_to_smaller_char",
@@ -312,6 +315,9 @@ protected void insertTableRows(String tableName)
                         "  DATE '2000-04-13', " +
                         "  'abc', " +
                         "  'abc', " +
+                        "  'ab', " +
+                        "  'cd', " +
+                        "  'a', " +
                         "  'Bigger Value', " +
                         "  'Hi  ', " +
                         "  'TrinoDB', " +
@@ -413,6 +419,9 @@ protected void insertTableRows(String tableName)
                         "  DATE '1900-01-01', " +
                         "  '\uD83D\uDCB0\uD83D\uDCB0\uD83D\uDCB0', " +
                         "  '\uD83D\uDCB0\uD83D\uDCB0\uD83D\uDCB0', " +
+                        "  '\uD83D\uDCB0\uD83D\uDCB0', " +
+                        "  '\uD83D\uDCB0\uD83D\uDCB0', " +
+                        "  '\uD83D\uDCB0', " +
                         "  '\uD83D\uDCB0\uD83D\uDCB0\uD83D\uDCB0\uD83D\uDCB0\uD83D\uDCB0', " +
                         "  '\uD83D\uDCB0 \uD83D\uDCB0\uD83D\uDCB0', " +
                         "  '\uD83D\uDCB0 \uD83D\uDCB0', " +
@@ -733,6 +742,15 @@ else if (isFormat.test("orc")) {
                 .put("char_to_smaller_char", ImmutableList.of(
                         "ab",
                         "\uD83D\uDCB0\uD83D\uDCB0"))
+                .put("char_to_string", ImmutableList.of(
+                        "ab",
+                        "\uD83D\uDCB0\uD83D\uDCB0"))
+                .put("char_to_bigger_varchar", ImmutableList.of(
+                        "cd",
+                        "\uD83D\uDCB0\uD83D\uDCB0"))
+                .put("char_to_smaller_varchar", ImmutableList.of(
+                        "a",
+                        "\uD83D\uDCB0"))
                 .put("timestamp_millis_to_date", ImmutableList.of(
                         java.sql.Date.valueOf("2022-12-31"),
                         java.sql.Date.valueOf("1970-01-01")))
@@ -1171,6 +1189,9 @@ private void assertProperAlteredTableSchema(String tableName)
                 row("date_to_bounded_varchar", "varchar(12)"),
                 row("char_to_bigger_char", "char(4)"),
                 row("char_to_smaller_char", "char(2)"),
+                row("char_to_string", "varchar"),
+                row("char_to_bigger_varchar", "varchar(4)"),
+                row("char_to_smaller_varchar", "varchar(2)"),
                 row("string_to_char", "char(1)"),
                 row("varchar_to_bigger_char", "char(6)"),
                 row("varchar_to_smaller_char", "char(2)"),
@@ -1280,6 +1301,9 @@ private void assertColumnTypes(
                 .put("date_to_bounded_varchar", VARCHAR)
                 .put("char_to_bigger_char", CHAR)
                 .put("char_to_smaller_char", CHAR)
+                .put("char_to_string", VARCHAR)
+                .put("char_to_bigger_varchar", VARCHAR)
+                .put("char_to_smaller_varchar", VARCHAR)
                 .put("string_to_char", CHAR)
                 .put("varchar_to_bigger_char", CHAR)
                 .put("varchar_to_smaller_char", CHAR)
@@ -1397,6 +1421,9 @@ private static void alterTableColumnTypes(String tableName)
         onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN varchar_to_special_double varchar_to_special_double double", tableName));
         onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN char_to_bigger_char char_to_bigger_char char(4)", tableName));
         onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN char_to_smaller_char char_to_smaller_char char(2)", tableName));
+        onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN char_to_string char_to_string string", tableName));
+        onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN char_to_bigger_varchar char_to_bigger_varchar varchar(4)", tableName));
+        onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN char_to_smaller_varchar char_to_smaller_varchar varchar(2)", tableName));
         onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN string_to_char string_to_char char(1)", tableName));
         onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN varchar_to_bigger_char varchar_to_bigger_char char(6)", tableName));
         onHive().executeQuery(format("ALTER TABLE %s CHANGE COLUMN varchar_to_smaller_char varchar_to_smaller_char char(2)", tableName));

testing/trino-product-tests/src/main/java/io/trino/tests/product/hive/TestHiveCoercionOnPartitionedTable.java

@@ -189,6 +189,9 @@ private static HiveTableDefinition.HiveTableDefinitionBuilder tableDefinitionBui
                         "    date_to_bounded_varchar            DATE," +
                         "    char_to_bigger_char                CHAR(3)," +
                         "    char_to_smaller_char               CHAR(3)," +
+                        "    char_to_string                     CHAR(3)," +
+                        "    char_to_bigger_varchar             CHAR(3)," +
+                        "    char_to_smaller_varchar            CHAR(3)," +
                         "    string_to_char                     STRING," +
                         "    varchar_to_bigger_char             VARCHAR(4)," +
                         "    varchar_to_smaller_char            VARCHAR(20)," +

testing/trino-product-tests/src/main/java/io/trino/tests/product/hive/TestHiveCoercionOnUnpartitionedTable.java

@@ -144,6 +144,9 @@ varchar_to_special_double          VARCHAR(40),
                             date_to_bounded_varchar            DATE,
                             char_to_bigger_char                CHAR(3),
                             char_to_smaller_char               CHAR(3),
+                            char_to_string                     CHAR(3),
+                            char_to_bigger_varchar             CHAR(3),
+                            char_to_smaller_varchar            CHAR(3),
                             string_to_char                     STRING,
                             varchar_to_bigger_char             VARCHAR(4),
                             varchar_to_smaller_char            VARCHAR(20),