[Spark] - Backport FunctionCatalog to Spark 3.2

spark/v3.2/spark/src/main/java/org/apache/iceberg/spark/BaseCatalog.java

@@ -18,18 +18,27 @@
  */
 package org.apache.iceberg.spark;
 
+import org.apache.iceberg.spark.functions.SparkFunctions;
 import org.apache.iceberg.spark.procedures.SparkProcedures;
 import org.apache.iceberg.spark.procedures.SparkProcedures.ProcedureBuilder;
 import org.apache.iceberg.spark.source.HasIcebergCatalog;
+import org.apache.spark.sql.catalyst.analysis.NoSuchFunctionException;
+import org.apache.spark.sql.catalyst.analysis.NoSuchNamespaceException;
 import org.apache.spark.sql.catalyst.analysis.NoSuchProcedureException;
+import org.apache.spark.sql.connector.catalog.FunctionCatalog;
 import org.apache.spark.sql.connector.catalog.Identifier;
 import org.apache.spark.sql.connector.catalog.StagingTableCatalog;
 import org.apache.spark.sql.connector.catalog.SupportsNamespaces;
+import org.apache.spark.sql.connector.catalog.functions.UnboundFunction;
 import org.apache.spark.sql.connector.iceberg.catalog.Procedure;
 import org.apache.spark.sql.connector.iceberg.catalog.ProcedureCatalog;
 
 abstract class BaseCatalog
-    implements StagingTableCatalog, ProcedureCatalog, SupportsNamespaces, HasIcebergCatalog {
+    implements StagingTableCatalog,
+        ProcedureCatalog,
+        SupportsNamespaces,
+        HasIcebergCatalog,
+        FunctionCatalog {
 
   @Override
   public Procedure loadProcedure(Identifier ident) throws NoSuchProcedureException {
@@ -38,7 +47,7 @@ public Procedure loadProcedure(Identifier ident) throws NoSuchProcedureException
 
     // namespace resolution is case insensitive until we have a way to configure case sensitivity in
     // catalogs
-    if (namespace.length == 1 && namespace[0].equalsIgnoreCase("system")) {
+    if (isSystemNamespace(namespace)) {
       ProcedureBuilder builder = SparkProcedures.newBuilder(name);
       if (builder != null) {
         return builder.withTableCatalog(this).build();
@@ -47,4 +56,40 @@ public Procedure loadProcedure(Identifier ident) throws NoSuchProcedureException
 
     throw new NoSuchProcedureException(ident);
   }
+
+  @Override
+  public Identifier[] listFunctions(String[] namespace) throws NoSuchNamespaceException {
+    if (namespace.length == 0 || isSystemNamespace(namespace)) {
+      return SparkFunctions.list().stream()
+          .map(name -> Identifier.of(namespace, name))
+          .toArray(Identifier[]::new);
+    } else if (namespaceExists(namespace)) {
+      return new Identifier[0];
+    }
+
+    throw new NoSuchNamespaceException(namespace);
+  }
+
+  @Override
+  public UnboundFunction loadFunction(Identifier ident) throws NoSuchFunctionException {
+    String[] namespace = ident.namespace();
+    String name = ident.name();
+
+    // Allow for empty namespace, as Spark's storage partitioned joins look up
+    // the corresponding functions to generate transforms for partitioning
+    // with an empty namespace, such as `bucket`.
+    // Otherwise, use `system` namespace.
+    if (namespace.length == 0 || isSystemNamespace(namespace)) {
+      UnboundFunction func = SparkFunctions.load(name);
+      if (func != null) {
+        return func;
+      }
+    }
+
+    throw new NoSuchFunctionException(ident);
+  }
+
+  private static boolean isSystemNamespace(String[] namespace) {
+    return namespace.length == 1 && namespace[0].equalsIgnoreCase("system");
+  }
 }

spark/v3.2/spark/src/main/java/org/apache/iceberg/spark/functions/IcebergVersionFunction.java

@@ -0,0 +1,96 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.iceberg.spark.functions;
+
+import org.apache.iceberg.IcebergBuild;
+import org.apache.spark.sql.catalyst.InternalRow;
+import org.apache.spark.sql.connector.catalog.functions.BoundFunction;
+import org.apache.spark.sql.connector.catalog.functions.ScalarFunction;
+import org.apache.spark.sql.connector.catalog.functions.UnboundFunction;
+import org.apache.spark.sql.types.DataType;
+import org.apache.spark.sql.types.DataTypes;
+import org.apache.spark.sql.types.StructType;
+import org.apache.spark.unsafe.types.UTF8String;
+
+/**
+ * A function for use in SQL that returns the current Iceberg version, e.g. {@code SELECT
+ * system.iceberg_version()} will return a String such as "0.14.0" or "0.15.0-SNAPSHOT"
+ */
+public class IcebergVersionFunction implements UnboundFunction {
+  @Override
+  public BoundFunction bind(StructType inputType) {
+    if (inputType.fields().length > 0) {
+      throw new UnsupportedOperationException(
+          String.format("Cannot bind: %s does not accept arguments", name()));
+    }
+
+    return new IcebergVersionFunctionImpl();
+  }
+
+  @Override
+  public String description() {
+    return name() + " - Returns the runtime Iceberg version";
+  }
+
+  @Override
+  public String name() {
+    return "iceberg_version";
+  }
+
+  // Implementing class cannot be private, otherwise Spark is unable to access the static invoke
+  // function during code-gen and calling the function fails
+  static class IcebergVersionFunctionImpl implements ScalarFunction<UTF8String> {
+    private static final UTF8String VERSION = UTF8String.fromString(IcebergBuild.version());
+
+    // magic function used in code-gen. must be named `invoke`.
+    public static UTF8String invoke() {
+      return VERSION;
+    }
+
+    @Override
+    public DataType[] inputTypes() {
+      return new DataType[0];
+    }
+
+    @Override
+    public DataType resultType() {
+      return DataTypes.StringType;
+    }
+
+    @Override
+    public boolean isResultNullable() {
+      return false;
+    }
+
+    @Override
+    public String canonicalName() {
+      return "iceberg." + name();
+    }
+
+    @Override
+    public String name() {
+      return "iceberg_version";
+    }
+
+    @Override
+    public UTF8String produceResult(InternalRow input) {
+      return invoke();
+    }
+  }
+}

spark/v3.2/spark/src/main/java/org/apache/iceberg/spark/functions/SparkFunctions.java

@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.iceberg.spark.functions;
+
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableMap;
+import org.apache.spark.sql.connector.catalog.functions.UnboundFunction;
+
+public class SparkFunctions {
+
+  private SparkFunctions() {}
+
+  private static final Map<String, UnboundFunction> FUNCTIONS =
+      ImmutableMap.of("iceberg_version", new IcebergVersionFunction());
+
+  private static final List<String> FUNCTION_NAMES = ImmutableList.copyOf(FUNCTIONS.keySet());
+
+  // Functions that are added to all Iceberg catalogs should be accessed with the `system`
+  // namespace. They can also be accessed with no namespace at all if qualified with the
+  // catalog name, e.g. my_hadoop_catalog.iceberg_version().
+  // As namespace resolution is handled by those rules in BaseCatalog, a list of names
+  // alone is returned.
+  public static List<String> list() {
+    return FUNCTION_NAMES;
+  }
+
+  public static UnboundFunction load(String name) {
+    // function resolution is case-insensitive to match the existing Spark behavior for functions
+    return FUNCTIONS.get(name.toLowerCase(Locale.ROOT));
+  }
+}

spark/v3.2/spark/src/test/java/org/apache/iceberg/spark/TestFunctionCatalog.java

@@ -0,0 +1,140 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.iceberg.spark;
+
+import org.apache.iceberg.AssertHelpers;
+import org.apache.iceberg.IcebergBuild;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.spark.functions.IcebergVersionFunction;
+import org.apache.spark.sql.AnalysisException;
+import org.apache.spark.sql.catalyst.analysis.NoSuchFunctionException;
+import org.apache.spark.sql.catalyst.analysis.NoSuchNamespaceException;
+import org.apache.spark.sql.connector.catalog.FunctionCatalog;
+import org.apache.spark.sql.connector.catalog.Identifier;
+import org.apache.spark.sql.connector.catalog.functions.UnboundFunction;
+import org.assertj.core.api.Assertions;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+public class TestFunctionCatalog extends SparkTestBaseWithCatalog {
+  private static final String[] EMPTY_NAMESPACE = new String[] {};
+  private static final String[] SYSTEM_NAMESPACE = new String[] {"system"};
+  private static final String[] DEFAULT_NAMESPACE = new String[] {"default"};
+  private static final String[] DB_NAMESPACE = new String[] {"db"};
+  private final FunctionCatalog asFunctionCatalog;
+
+  public TestFunctionCatalog() {
+    this.asFunctionCatalog = castToFunctionCatalog(catalogName);
+  }
+
+  @Before
+  public void createDefaultNamespace() {
+    sql("CREATE NAMESPACE IF NOT EXISTS %s", catalogName + ".default");
+  }
+
+  @After
+  public void dropDefaultNamespace() {
+    sql("DROP NAMESPACE IF EXISTS %s", catalogName + ".default");
+  }
+
+  @Test
+  public void testListFunctionsViaCatalog() throws NoSuchNamespaceException {
+    Assertions.assertThat(asFunctionCatalog.listFunctions(EMPTY_NAMESPACE))
+        .anyMatch(func -> "iceberg_version".equals(func.name()));
+
+    Assertions.assertThat(asFunctionCatalog.listFunctions(SYSTEM_NAMESPACE))
+        .anyMatch(func -> "iceberg_version".equals(func.name()));
+
+    Assert.assertArrayEquals(
+        "Listing functions in an existing namespace that's not system should not throw",
+        new Identifier[0],
+        asFunctionCatalog.listFunctions(DEFAULT_NAMESPACE));
+
+    AssertHelpers.assertThrows(
+        "Listing functions in a namespace that does not exist should throw",
+        NoSuchNamespaceException.class,
+        "Namespace 'db' not found",
+        () -> asFunctionCatalog.listFunctions(DB_NAMESPACE));
+  }
+
+  @Test
+  public void testLoadFunctions() throws NoSuchFunctionException {
+    for (String[] namespace : ImmutableList.of(EMPTY_NAMESPACE, SYSTEM_NAMESPACE)) {
+      Identifier identifier = Identifier.of(namespace, "iceberg_version");
+      UnboundFunction func = asFunctionCatalog.loadFunction(identifier);
+
+      Assertions.assertThat(func)
+          .isNotNull()
+          .isInstanceOf(UnboundFunction.class)
+          .isExactlyInstanceOf(IcebergVersionFunction.class);
+    }
+
+    AssertHelpers.assertThrows(
+        "Cannot load a function if it's not used with the system namespace or the empty namespace",
+        NoSuchFunctionException.class,
+        "Undefined function: default.iceberg_version",
+        () -> asFunctionCatalog.loadFunction(Identifier.of(DEFAULT_NAMESPACE, "iceberg_version")));
+
+    Identifier undefinedFunction = Identifier.of(SYSTEM_NAMESPACE, "undefined_function");
+    AssertHelpers.assertThrows(
+        "Cannot load a function that does not exist",
+        NoSuchFunctionException.class,
+        "Undefined function: system.undefined_function",
+        () -> asFunctionCatalog.loadFunction(undefinedFunction));
+
+    AssertHelpers.assertThrows(
+        "Using an undefined function from SQL should fail analysis",
+        AnalysisException.class,
+        "Undefined function",
+        () -> sql("SELECT undefined_function(1, 2)"));
+  }
+
+  @Test
+  public void testCallingFunctionInSQLEndToEnd() {
+    String buildVersion = IcebergBuild.version();
+
+    Assert.assertEquals(
+        "Should be able to use the Iceberg version function from the fully qualified system namespace",
+        buildVersion,
+        scalarSql("SELECT %s.system.iceberg_version()", catalogName));
+
+    Assert.assertEquals(
+        "Should be able to use the Iceberg version function when fully qualified without specifying a namespace",
+        buildVersion,
+        scalarSql("SELECT %s.iceberg_version()", catalogName));
+
+    sql("USE %s", catalogName);
+
+    Assert.assertEquals(
+        "Should be able to call iceberg_version from system namespace without fully qualified name when using Iceberg catalog",
+        buildVersion,
+        scalarSql("SELECT system.iceberg_version()"));
+
+    Assert.assertEquals(
+        "Should be able to call iceberg_version from empty namespace without fully qualified name when using Iceberg catalog",
+        buildVersion,
+        scalarSql("SELECT iceberg_version()"));
+  }
+
+  private FunctionCatalog castToFunctionCatalog(String name) {
+    return (FunctionCatalog) spark.sessionState().catalogManager().catalog(name);
+  }
+}