gaborkaszab commented on code in PR #12774:
URL: https://github.com/apache/iceberg/pull/12774#discussion_r2438788058


##########
core/src/main/java/org/apache/iceberg/formats/ReadBuilder.java:
##########
@@ -0,0 +1,118 @@
+/*
+ * 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.formats;
+
+import java.nio.ByteBuffer;
+import java.util.Map;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.expressions.Expression;
+import org.apache.iceberg.io.CloseableIterable;
+import org.apache.iceberg.mapping.NameMapping;
+
+/**
+ * Builder interface for creating file readers across supported data file 
formats. The {@link
+ * FormatModel} implementations provides appropriate {@link ReadBuilder} 
instances
+ *
+ * <p>The {@link ReadBuilder} follows the builder pattern to configure and 
create {@link
+ * CloseableIterable} instances that read data from source files. 
Configuration options include
+ * schema projection, predicate filtering, record batching, and encryption 
settings.
+ *
+ * <p>This interface is directly exposed to users for parameterizing readers.
+ */
+public interface ReadBuilder {
+  /**
+   * Restricts the read to the given range: [start, start + length).
+   *
+   * @param newStart the start position for this read
+   * @param newLength the length of the range this read should scan
+   */
+  ReadBuilder split(long newStart, long newLength);
+
+  /** Set the projection schema. */
+  ReadBuilder project(Schema schema);
+
+  /** Sets the expected output schema. If not provided derived from the {@link 
#project(Schema)}. */
+  default ReadBuilder outputSchema(Object schema) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+
+  /**
+   * Configures whether filtering should be case-sensitive. If the reader 
supports filtering, it
+   * must respect this setting.
+   *
+   * @param caseSensitive indicates if filtering is case-sensitive
+   */
+  ReadBuilder caseSensitive(boolean caseSensitive);
+
+  /**
+   * Pushes down the {@link Expression} filter for the reader to prevent 
reading unnecessary
+   * records. Some readers might not be able to filter some part of the 
exception. In this case the
+   * reader might return unfiltered or partially filtered rows. It is the 
caller's responsibility to
+   * apply the filter again. The default implementation sets the filter to be 
case-sensitive.

Review Comment:
   nit: "The default implementation sets the filter to be case-sensitive." 
Isn't this rather relevant for the `caseSensitive` function?



##########
core/src/main/java/org/apache/iceberg/formats/ReadBuilder.java:
##########
@@ -0,0 +1,118 @@
+/*
+ * 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.formats;
+
+import java.nio.ByteBuffer;
+import java.util.Map;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.expressions.Expression;
+import org.apache.iceberg.io.CloseableIterable;
+import org.apache.iceberg.mapping.NameMapping;
+
+/**
+ * Builder interface for creating file readers across supported data file 
formats. The {@link
+ * FormatModel} implementations provides appropriate {@link ReadBuilder} 
instances
+ *
+ * <p>The {@link ReadBuilder} follows the builder pattern to configure and 
create {@link
+ * CloseableIterable} instances that read data from source files. 
Configuration options include
+ * schema projection, predicate filtering, record batching, and encryption 
settings.
+ *
+ * <p>This interface is directly exposed to users for parameterizing readers.
+ */
+public interface ReadBuilder {
+  /**
+   * Restricts the read to the given range: [start, start + length).
+   *
+   * @param newStart the start position for this read
+   * @param newLength the length of the range this read should scan
+   */
+  ReadBuilder split(long newStart, long newLength);
+
+  /** Set the projection schema. */
+  ReadBuilder project(Schema schema);
+
+  /** Sets the expected output schema. If not provided derived from the {@link 
#project(Schema)}. */
+  default ReadBuilder outputSchema(Object schema) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+
+  /**
+   * Configures whether filtering should be case-sensitive. If the reader 
supports filtering, it
+   * must respect this setting.
+   *
+   * @param caseSensitive indicates if filtering is case-sensitive
+   */
+  ReadBuilder caseSensitive(boolean caseSensitive);
+
+  /**
+   * Pushes down the {@link Expression} filter for the reader to prevent 
reading unnecessary
+   * records. Some readers might not be able to filter some part of the 
exception. In this case the
+   * reader might return unfiltered or partially filtered rows. It is the 
caller's responsibility to
+   * apply the filter again. The default implementation sets the filter to be 
case-sensitive.
+   *
+   * @param filter the filter to set
+   */
+  ReadBuilder filter(Expression filter);
+
+  /**
+   * Sets configuration key/value pairs for the reader. Reader builders should 
ignore configuration
+   * keys not known for them.
+   */
+  ReadBuilder set(String key, String value);

Review Comment:
   nit: The similar function in WriteBuilder has a more structured comment. 
Would be nice to follow that pattern in this class too.



##########
core/src/main/java/org/apache/iceberg/formats/WriteBuilder.java:
##########
@@ -0,0 +1,115 @@
+/*
+ * 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.formats;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Map;
+import org.apache.iceberg.FileContent;
+import org.apache.iceberg.MetricsConfig;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.io.FileAppender;
+
+/**
+ * Builder interface for creating file writers across supported data file 
formats. The {@link
+ * FormatModel} implementations provide the appropriate {@link WriteBuilder} 
instances.
+ *
+ * <p>The {@link WriteBuilder} follows the builder pattern to configure and 
create {@link
+ * FileAppender} instances that write data to the target output files.
+ *
+ * <p>This interface is directly exposed to users for parameterizing when only 
an appender is
+ * required.
+ */
+public interface WriteBuilder {
+  /** Set the file schema. */
+  WriteBuilder schema(Schema schema);
+
+  /**
+   * Sets the input schema accepted by the writer. If not provided derived 
from the {@link
+   * #schema(Schema)}.
+   */
+  WriteBuilder inputSchema(Object schema);
+
+  /**
+   * Set a writer configuration property which affects the writer behavior.
+   *
+   * @param property a writer config property name
+   * @param value config value
+   * @return this for method chaining
+   */
+  WriteBuilder set(String property, String value);
+
+  /**
+   * Sets multiple writer configuration properties that affect the writer 
behavior.
+   *
+   * @param properties writer config properties to set
+   * @return this for method chaining
+   */
+  default WriteBuilder setAll(Map<String, String> properties) {
+    properties.forEach(this::set);
+    return this;
+  }
+
+  /**
+   * Set a file metadata property in the created file.
+   *
+   * @param property a file metadata property name
+   * @param value config value
+   * @return this for method chaining
+   */
+  WriteBuilder meta(String property, String value);
+
+  /**
+   * Sets multiple file metadata properties in the created file.
+   *
+   * @param properties file metadata properties to set
+   * @return this for method chaining
+   */
+  default WriteBuilder meta(Map<String, String> properties) {
+    properties.forEach(this::meta);
+    return this;
+  }
+
+  /**
+   * Based on the target file content the generated {@link FileAppender} needs 
different
+   * configuration.
+   */
+  WriteBuilder content(FileContent content);
+
+  /** Sets the metrics configuration used for collecting column metrics for 
the created file. */
+  WriteBuilder metricsConfig(MetricsConfig metricsConfig);
+
+  /** Overwrite the file if it already exists. By default, overwrite is 
disabled. */
+  WriteBuilder overwrite();
+
+  /**
+   * Sets the encryption key used for writing the file. If the writer does not 
support encryption,
+   * then an exception should be thrown.
+   */
+  WriteBuilder withFileEncryptionKey(ByteBuffer encryptionKey);
+
+  /**
+   * Sets the additional authentication data (AAD) prefix used for writing the 
file. If the reader

Review Comment:
   nit: "If the reader does not support encryption" -> "If the writer..."



##########
core/src/main/java/org/apache/iceberg/formats/FormatModelRegistry.java:
##########
@@ -0,0 +1,241 @@
+/*
+ * 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.formats;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import org.apache.iceberg.DataFile;
+import org.apache.iceberg.DeleteFile;
+import org.apache.iceberg.FileContent;
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.common.DynMethods;
+import org.apache.iceberg.deletes.EqualityDeleteWriter;
+import org.apache.iceberg.deletes.PositionDelete;
+import org.apache.iceberg.deletes.PositionDeleteWriter;
+import org.apache.iceberg.encryption.EncryptedOutputFile;
+import org.apache.iceberg.io.DataWriter;
+import org.apache.iceberg.io.InputFile;
+import 
org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+import org.apache.iceberg.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A registry that manages file-format-specific readers and writers through a 
unified object model
+ * factory interface.
+ *
+ * <p>This registry provides access to {@link ReadBuilder}s for data 
consumption and various writer
+ * builders:
+ *
+ * <ul>
+ *   <li>{@link WriteBuilder} for basic file writing,
+ *   <li>{@link DataWriteBuilder} for data files,
+ *   <li>{@link EqualityDeleteWriteBuilder} for equality deletes,
+ *   <li>{@link PositionDeleteWriteBuilder} for position deletes.
+ * </ul>
+ *
+ * The appropriate builder is selected based on {@link FileFormat} and object 
model name.
+ *
+ * <p>{@link FormatModel} objects are registered through {@link 
#register(FormatModel)} and used for
+ * creating readers and writers. Read builders are returned directly from the 
factory. Write
+ * builders may be wrapped in specialized content file writer implementations 
depending on the
+ * requested builder type.
+ */
+public final class FormatModelRegistry {
+  private static final Logger LOG = 
LoggerFactory.getLogger(FormatModelRegistry.class);
+  // The list of classes which are used for registering the reader and writer 
builders
+  private static final List<String> CLASSES_TO_REGISTER = ImmutableList.of();
+
+  private static final Map<Pair<FileFormat, Class<?>>, FormatModel<?, ?>> 
MODELS =
+      Maps.newConcurrentMap();
+
+  private FormatModelRegistry() {}
+
+  /**
+   * Registers an {@link FormatModel} in this registry.
+   *
+   * <p>The {@link FormatModel} creates readers and writers for a specific 
combinations of file
+   * format (Parquet, ORC, Avro) and object model (for example: "generic", 
"spark", "flink", etc.).
+   * Registering custom factories allows integration of new data processing 
engines for the
+   * supported file formats with Iceberg's file access mechanisms.
+   *
+   * <p>Each factory must be uniquely identified by its combination of file 
format and object model
+   * name. This uniqueness constraint prevents ambiguity when selecting 
factories for read and write
+   * operations.
+   *
+   * @param formatModel the factory implementation to register
+   * @throws IllegalArgumentException if a factory is already registered for 
the combination of
+   *     {@link FormatModel#format()} and {@link FormatModel#type()}
+   */
+  public static void register(FormatModel<?, ?> formatModel) {
+    Pair<FileFormat, Class<?>> key = Pair.of(formatModel.format(), 
formatModel.type());
+
+    FormatModel<?, ?> existing = MODELS.get(key);
+    Preconditions.checkArgument(
+        existing == null || checkFormatModelEquals(existing, formatModel),
+        "Cannot register %s: %s is registered for format=%s type=%s 
schemaType=%s",
+        formatModel.getClass(),
+        existing == null ? null : existing.getClass(),
+        key.first(),
+        key.second(),
+        existing == null ? null : existing.schemaType());
+
+    MODELS.put(key, formatModel);
+  }
+
+  private static boolean checkFormatModelEquals(

Review Comment:
   nit: `isEqual` (without the s) or simply `equals`?



##########
core/src/main/java/org/apache/iceberg/formats/FormatModel.java:
##########
@@ -0,0 +1,86 @@
+/*
+ * 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.formats;
+
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.io.InputFile;
+import org.apache.iceberg.io.OutputFile;
+
+/**
+ * Interface that provides a unified abstraction for converting between data 
file formats and
+ * input/output data representations.
+ *
+ * <p>{@link FormatModel} serves as a bridge between storage formats ({@link 
FileFormat}) and
+ * expected input/output data structures, optimizing performance through 
direct conversion without
+ * intermediate representations. File format implementations handle the 
low-level parsing details
+ * while the object model determines the in-memory representation used for the 
parsed data.
+ * Together, these provide a consistent API for consuming data files while 
optimizing for specific
+ * processing engines.
+ *
+ * <p>Iceberg provides some built-in object models and processing engines can 
implement custom
+ * object models to integrate with Iceberg's file reading and writing 
capabilities.
+ *
+ * @param <D> output type used for reading data, and input type for writing 
data and deletes
+ * @param <S> the type of the schema for the input/output data
+ */
+public interface FormatModel<D, S> {
+  /** The file format which is read/written by the object model. */
+  FileFormat format();

Review Comment:
   Does this mean that in order to have a format model for other than what is 
covered by FileFormat now it's required to extend the FileFormat enum too?



##########
core/src/main/java/org/apache/iceberg/formats/FormatModelRegistry.java:
##########
@@ -0,0 +1,241 @@
+/*
+ * 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.formats;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import org.apache.iceberg.DataFile;
+import org.apache.iceberg.DeleteFile;
+import org.apache.iceberg.FileContent;
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.common.DynMethods;
+import org.apache.iceberg.deletes.EqualityDeleteWriter;
+import org.apache.iceberg.deletes.PositionDelete;
+import org.apache.iceberg.deletes.PositionDeleteWriter;
+import org.apache.iceberg.encryption.EncryptedOutputFile;
+import org.apache.iceberg.io.DataWriter;
+import org.apache.iceberg.io.InputFile;
+import 
org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+import org.apache.iceberg.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A registry that manages file-format-specific readers and writers through a 
unified object model
+ * factory interface.
+ *
+ * <p>This registry provides access to {@link ReadBuilder}s for data 
consumption and various writer
+ * builders:
+ *
+ * <ul>
+ *   <li>{@link WriteBuilder} for basic file writing,
+ *   <li>{@link DataWriteBuilder} for data files,
+ *   <li>{@link EqualityDeleteWriteBuilder} for equality deletes,
+ *   <li>{@link PositionDeleteWriteBuilder} for position deletes.
+ * </ul>
+ *
+ * The appropriate builder is selected based on {@link FileFormat} and object 
model name.
+ *
+ * <p>{@link FormatModel} objects are registered through {@link 
#register(FormatModel)} and used for
+ * creating readers and writers. Read builders are returned directly from the 
factory. Write
+ * builders may be wrapped in specialized content file writer implementations 
depending on the
+ * requested builder type.
+ */
+public final class FormatModelRegistry {
+  private static final Logger LOG = 
LoggerFactory.getLogger(FormatModelRegistry.class);
+  // The list of classes which are used for registering the reader and writer 
builders
+  private static final List<String> CLASSES_TO_REGISTER = ImmutableList.of();
+
+  private static final Map<Pair<FileFormat, Class<?>>, FormatModel<?, ?>> 
MODELS =
+      Maps.newConcurrentMap();
+
+  private FormatModelRegistry() {}
+
+  /**
+   * Registers an {@link FormatModel} in this registry.
+   *
+   * <p>The {@link FormatModel} creates readers and writers for a specific 
combinations of file
+   * format (Parquet, ORC, Avro) and object model (for example: "generic", 
"spark", "flink", etc.).
+   * Registering custom factories allows integration of new data processing 
engines for the
+   * supported file formats with Iceberg's file access mechanisms.
+   *
+   * <p>Each factory must be uniquely identified by its combination of file 
format and object model
+   * name. This uniqueness constraint prevents ambiguity when selecting 
factories for read and write
+   * operations.
+   *
+   * @param formatModel the factory implementation to register
+   * @throws IllegalArgumentException if a factory is already registered for 
the combination of
+   *     {@link FormatModel#format()} and {@link FormatModel#type()}
+   */
+  public static void register(FormatModel<?, ?> formatModel) {
+    Pair<FileFormat, Class<?>> key = Pair.of(formatModel.format(), 
formatModel.type());
+
+    FormatModel<?, ?> existing = MODELS.get(key);
+    Preconditions.checkArgument(
+        existing == null || checkFormatModelEquals(existing, formatModel),
+        "Cannot register %s: %s is registered for format=%s type=%s 
schemaType=%s",
+        formatModel.getClass(),
+        existing == null ? null : existing.getClass(),
+        key.first(),
+        key.second(),
+        existing == null ? null : existing.schemaType());
+
+    MODELS.put(key, formatModel);
+  }
+
+  private static boolean checkFormatModelEquals(
+      FormatModel<?, ?> model1, FormatModel<?, ?> model2) {
+    return Objects.equals(model1.getClass().getName(), 
model2.getClass().getName())
+        && Objects.equals(model1.type().getName(), model2.type().getName())
+        && Objects.equals(
+            model1.schemaType() == null ? null : model1.schemaType().getName(),
+            model2.schemaType() == null ? null : 
model2.schemaType().getName());
+  }
+
+  @SuppressWarnings("CatchBlockLogException")
+  private static void registerSupportedFormats() {
+    // Uses dynamic methods to call the `register` for the listed classes
+    for (String classToRegister : CLASSES_TO_REGISTER) {
+      try {
+        
DynMethods.builder("register").impl(classToRegister).buildStaticChecked().invoke();
+      } catch (NoSuchMethodException e) {
+        // failing to register a factory is normal and does not require a 
stack trace
+        LOG.info("Unable to register {}: {}", classToRegister, e.getMessage());
+      }
+    }
+  }
+
+  static {
+    registerSupportedFormats();
+  }
+
+  /**
+   * Returns a reader builder for the specified file format and object model.
+   *
+   * <p>The returned {@link ReadBuilder} provides a fluent interface for 
configuring how data is
+   * read from the input file and converted to the output objects. The builder 
supports
+   * configuration options like schema projection, predicate pushdown, batch 
size and encryption.
+   *
+   * @param format the file format (Parquet, Avro, ORC) that determines the 
parsing implementation
+   * @param type the output type
+   * @param inputFile source file to read data from
+   * @param <D> the type of data records the reader will produce
+   * @return a configured reader builder for the specified format and object 
model
+   */
+  public static <D, S> ReadBuilder readBuilder(
+      FileFormat format, Class<D> type, InputFile inputFile) {
+    FormatModel<D, S> factory = factoryFor(format, type);
+    return factory.readBuilder(inputFile);
+  }
+
+  /**
+   * Returns a writer builder for generating a {@link DataFile}.
+   *
+   * <p>The returned builder produces a writer that accepts records defined by 
the specified object
+   * model and persists them using the provided file format. Unlike basic 
writers, this writer
+   * collects file metadata during the writing process and generates a {@link 
DataFile} that can be
+   * used for table operations.
+   *
+   * @param format the file format used for writing
+   * @param type the input type
+   * @param outputFile destination for the written data
+   * @param <D> the type of data records the writer will accept
+   * @param <S> the type of the input schema for the writer
+   * @return a configured data write builder for creating a {@link DataWriter}
+   */
+  public static <D, S> DataWriteBuilder<D, S> dataWriteBuilder(
+      FileFormat format, Class<D> type, EncryptedOutputFile outputFile) {
+    FormatModel<D, S> factory = factoryFor(format, type);
+    WriteBuilder writeBuilder =
+        
factory.writeBuilder(outputFile.encryptingOutputFile()).content(FileContent.DATA);
+    return ContentFileWriteBuilderImpl.forDataFile(
+        writeBuilder, outputFile.encryptingOutputFile().location(), format);
+  }
+
+  /**
+   * Creates a writer builder for generating a {@link DeleteFile} with 
equality deletes.
+   *
+   * <p>The returned builder produces a writer that accepts records defined by 
the specified object
+   * model and persists them using the given file format. The writer persists 
equality delete
+   * records that identify rows to be deleted based on the configured equality 
fields, producing a
+   * {@link DeleteFile} that can be used for table operations.
+   *
+   * @param format the file format used for writing
+   * @param type the input type
+   * @param outputFile destination for the written data
+   * @param <D> the type of data records the writer will accept
+   * @param <S> the type of the input schema for the writer
+   * @return a configured delete write builder for creating an {@link 
EqualityDeleteWriter}
+   */
+  public static <D, S> EqualityDeleteWriteBuilder<D, S> 
equalityDeleteWriteBuilder(
+      FileFormat format, Class<D> type, EncryptedOutputFile outputFile) {
+    FormatModel<D, S> factory = factoryFor(format, type);
+    WriteBuilder writeBuilder =
+        factory
+            .writeBuilder(outputFile.encryptingOutputFile())
+            .content(FileContent.EQUALITY_DELETES);
+    return ContentFileWriteBuilderImpl.forEqualityDelete(
+        writeBuilder, outputFile.encryptingOutputFile().location(), format);
+  }
+
+  /**
+   * Creates a writer builder for generating a {@link DeleteFile} with 
position-based deletes.
+   *
+   * <p>The returned builder produces a writer that accepts records defined by 
the specified object
+   * model and persists them using the given file format. The writer accepts 
{@link PositionDelete}
+   * records that identify rows to be deleted by file path and position, 
producing a {@link
+   * DeleteFile} that can be used for table operations.
+   *
+   * @param format the file format used for writing
+   * @param outputFile destination for the written data
+   * @return a configured delete write builder for creating a {@link 
PositionDeleteWriter}
+   */
+  public static PositionDeleteWriteBuilder positionDeleteWriteBuilder(
+      FileFormat format, EncryptedOutputFile outputFile) {
+    FormatModel<PositionDelete<?>, ?> factory = 
factoryForPositionDelete(format);
+    WriteBuilder writeBuilder =
+        factory
+            .writeBuilder(outputFile.encryptingOutputFile())
+            .content(FileContent.POSITION_DELETES);
+    return ContentFileWriteBuilderImpl.forPositionDelete(
+        writeBuilder, outputFile.encryptingOutputFile().location(), format);
+  }
+
+  @VisibleForTesting
+  static Map<Pair<FileFormat, Class<?>>, FormatModel<?, ?>> models() {
+    return MODELS;
+  }
+
+  @SuppressWarnings("unchecked")
+  private static <D, S> FormatModel<D, S> factoryFor(FileFormat format, 
Class<D> type) {
+    FormatModel<D, S> model = ((FormatModel<D, S>) MODELS.get(Pair.of(format, 
type)));
+    Preconditions.checkArgument(
+        model != null, "Format model is not registered for %s and %s", format, 
type);
+    return model;
+  }
+
+  @SuppressWarnings("unchecked")
+  private static FormatModel<PositionDelete<?>, ?> 
factoryForPositionDelete(FileFormat format) {

Review Comment:
   Do you need a separate factory function for pos deletes? Can't you use the 
other `factoryFor` method passing PositionDelete.class as arg and do the return 
type conversion at the calcite?



##########
core/src/main/java/org/apache/iceberg/formats/FormatModelRegistry.java:
##########
@@ -0,0 +1,241 @@
+/*
+ * 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.formats;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import org.apache.iceberg.DataFile;
+import org.apache.iceberg.DeleteFile;
+import org.apache.iceberg.FileContent;
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.common.DynMethods;
+import org.apache.iceberg.deletes.EqualityDeleteWriter;
+import org.apache.iceberg.deletes.PositionDelete;
+import org.apache.iceberg.deletes.PositionDeleteWriter;
+import org.apache.iceberg.encryption.EncryptedOutputFile;
+import org.apache.iceberg.io.DataWriter;
+import org.apache.iceberg.io.InputFile;
+import 
org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+import org.apache.iceberg.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A registry that manages file-format-specific readers and writers through a 
unified object model
+ * factory interface.
+ *
+ * <p>This registry provides access to {@link ReadBuilder}s for data 
consumption and various writer
+ * builders:
+ *
+ * <ul>
+ *   <li>{@link WriteBuilder} for basic file writing,
+ *   <li>{@link DataWriteBuilder} for data files,
+ *   <li>{@link EqualityDeleteWriteBuilder} for equality deletes,
+ *   <li>{@link PositionDeleteWriteBuilder} for position deletes.
+ * </ul>
+ *
+ * The appropriate builder is selected based on {@link FileFormat} and object 
model name.
+ *
+ * <p>{@link FormatModel} objects are registered through {@link 
#register(FormatModel)} and used for
+ * creating readers and writers. Read builders are returned directly from the 
factory. Write
+ * builders may be wrapped in specialized content file writer implementations 
depending on the
+ * requested builder type.
+ */
+public final class FormatModelRegistry {
+  private static final Logger LOG = 
LoggerFactory.getLogger(FormatModelRegistry.class);
+  // The list of classes which are used for registering the reader and writer 
builders
+  private static final List<String> CLASSES_TO_REGISTER = ImmutableList.of();
+
+  private static final Map<Pair<FileFormat, Class<?>>, FormatModel<?, ?>> 
MODELS =
+      Maps.newConcurrentMap();
+
+  private FormatModelRegistry() {}
+
+  /**
+   * Registers an {@link FormatModel} in this registry.
+   *
+   * <p>The {@link FormatModel} creates readers and writers for a specific 
combinations of file
+   * format (Parquet, ORC, Avro) and object model (for example: "generic", 
"spark", "flink", etc.).
+   * Registering custom factories allows integration of new data processing 
engines for the
+   * supported file formats with Iceberg's file access mechanisms.
+   *
+   * <p>Each factory must be uniquely identified by its combination of file 
format and object model
+   * name. This uniqueness constraint prevents ambiguity when selecting 
factories for read and write
+   * operations.
+   *
+   * @param formatModel the factory implementation to register
+   * @throws IllegalArgumentException if a factory is already registered for 
the combination of
+   *     {@link FormatModel#format()} and {@link FormatModel#type()}
+   */
+  public static void register(FormatModel<?, ?> formatModel) {
+    Pair<FileFormat, Class<?>> key = Pair.of(formatModel.format(), 
formatModel.type());
+
+    FormatModel<?, ?> existing = MODELS.get(key);
+    Preconditions.checkArgument(
+        existing == null || checkFormatModelEquals(existing, formatModel),
+        "Cannot register %s: %s is registered for format=%s type=%s 
schemaType=%s",
+        formatModel.getClass(),
+        existing == null ? null : existing.getClass(),
+        key.first(),
+        key.second(),
+        existing == null ? null : existing.schemaType());
+
+    MODELS.put(key, formatModel);
+  }
+
+  private static boolean checkFormatModelEquals(
+      FormatModel<?, ?> model1, FormatModel<?, ?> model2) {
+    return Objects.equals(model1.getClass().getName(), 
model2.getClass().getName())
+        && Objects.equals(model1.type().getName(), model2.type().getName())
+        && Objects.equals(
+            model1.schemaType() == null ? null : model1.schemaType().getName(),
+            model2.schemaType() == null ? null : 
model2.schemaType().getName());
+  }
+
+  @SuppressWarnings("CatchBlockLogException")
+  private static void registerSupportedFormats() {
+    // Uses dynamic methods to call the `register` for the listed classes
+    for (String classToRegister : CLASSES_TO_REGISTER) {
+      try {
+        
DynMethods.builder("register").impl(classToRegister).buildStaticChecked().invoke();
+      } catch (NoSuchMethodException e) {
+        // failing to register a factory is normal and does not require a 
stack trace
+        LOG.info("Unable to register {}: {}", classToRegister, e.getMessage());
+      }
+    }
+  }
+
+  static {
+    registerSupportedFormats();
+  }
+
+  /**
+   * Returns a reader builder for the specified file format and object model.
+   *
+   * <p>The returned {@link ReadBuilder} provides a fluent interface for 
configuring how data is
+   * read from the input file and converted to the output objects. The builder 
supports

Review Comment:
   `The builder supports
      * configuration options like schema projection, predicate pushdown, batch 
size and encryption.`
   nit: for me this seems relevant for the ReadBuilder class and probably not 
here.



##########
core/src/main/java/org/apache/iceberg/formats/WriteBuilder.java:
##########
@@ -0,0 +1,115 @@
+/*
+ * 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.formats;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Map;
+import org.apache.iceberg.FileContent;
+import org.apache.iceberg.MetricsConfig;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.io.FileAppender;
+
+/**
+ * Builder interface for creating file writers across supported data file 
formats. The {@link
+ * FormatModel} implementations provide the appropriate {@link WriteBuilder} 
instances.
+ *
+ * <p>The {@link WriteBuilder} follows the builder pattern to configure and 
create {@link
+ * FileAppender} instances that write data to the target output files.
+ *
+ * <p>This interface is directly exposed to users for parameterizing when only 
an appender is
+ * required.
+ */
+public interface WriteBuilder {
+  /** Set the file schema. */
+  WriteBuilder schema(Schema schema);
+
+  /**
+   * Sets the input schema accepted by the writer. If not provided derived 
from the {@link
+   * #schema(Schema)}.
+   */
+  WriteBuilder inputSchema(Object schema);
+
+  /**
+   * Set a writer configuration property which affects the writer behavior.

Review Comment:
   nit: ReadBuilder comment mentions that unknown config is ignored. Should we 
mention it here (and for setAll) too?



##########
core/src/main/java/org/apache/iceberg/formats/FormatModelRegistry.java:
##########
@@ -0,0 +1,240 @@
+/*
+ * 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.formats;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import org.apache.iceberg.DataFile;
+import org.apache.iceberg.DeleteFile;
+import org.apache.iceberg.FileContent;
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.common.DynMethods;
+import org.apache.iceberg.deletes.EqualityDeleteWriter;
+import org.apache.iceberg.deletes.PositionDelete;
+import org.apache.iceberg.deletes.PositionDeleteWriter;
+import org.apache.iceberg.encryption.EncryptedOutputFile;
+import org.apache.iceberg.io.DataWriter;
+import org.apache.iceberg.io.InputFile;
+import 
org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+import org.apache.iceberg.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A registry that manages file-format-specific readers and writers through a 
unified object model
+ * factory interface.
+ *
+ * <p>This registry provides access to {@link ReadBuilder}s for data 
consumption and various writer
+ * builders:
+ *
+ * <ul>
+ *   <li>{@link WriteBuilder} for basic file writing,
+ *   <li>{@link DataWriteBuilder} for data files,
+ *   <li>{@link EqualityDeleteWriteBuilder} for equality deletes,
+ *   <li>{@link PositionDeleteWriteBuilder} for position deletes.
+ * </ul>
+ *
+ * The appropriate builder is selected based on {@link FileFormat} and object 
model name.
+ *
+ * <p>{@link FormatModel} objects are registered through {@link 
#register(FormatModel)} and used for
+ * creating readers and writers. Read builders are returned directly from the 
factory. Write
+ * builders may be wrapped in specialized content file writer implementations 
depending on the
+ * requested builder type.
+ */
+public final class FormatModelRegistry {
+  private static final Logger LOG = 
LoggerFactory.getLogger(FormatModelRegistry.class);
+  // The list of classes which are used for registering the reader and writer 
builders
+  private static final List<String> CLASSES_TO_REGISTER = ImmutableList.of();
+
+  private static final Map<Pair<FileFormat, Class<?>>, FormatModel<?, ?>> 
MODELS =

Review Comment:
   nit: some comment about the params would be helpful



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