adbc-drivers
diff --git a/‎csharp/doc/PECO-2788-cloudfetch-protocol-agnostic-design.md‎
Lines changed: 1966 additions & 0 deletions b/‎csharp/doc/PECO-2788-cloudfetch-protocol-agnostic-design.md‎
Lines changed: 1966 additions & 0 deletions
diff --git a/‎csharp/src/Reader/BaseDatabricksReader.cs‎
Lines changed: 18 additions & 39 deletions b/‎csharp/src/Reader/BaseDatabricksReader.cs‎
Lines changed: 18 additions & 39 deletions
diff --git a/‎csharp/src/Reader/CloudFetch/CloudFetchConfiguration.cs‎
Lines changed: 206 additions & 0 deletions b/‎csharp/src/Reader/CloudFetch/CloudFetchConfiguration.cs‎
Lines changed: 206 additions & 0 deletions
@@ -30,70 +30,49 @@
 namespace Apache.Arrow.Adbc.Drivers.Databricks.Reader
 {
     /// <summary>
-    /// Base class for Databricks readers that handles common functionality of DatabricksReader and CloudFetchReader
+    /// Base class for Databricks readers that handles common functionality of DatabricksReader and CloudFetchReader.
+    /// Protocol-agnostic - works with both Thrift and REST implementations.
     /// </summary>
     internal abstract class BaseDatabricksReader : TracingReader
     {
-        protected IHiveServer2Statement statement;
         protected readonly Schema schema;
-        protected readonly IResponse response;
+        protected readonly IResponse? response;  // Nullable for protocol-agnostic usage
         protected readonly bool isLz4Compressed;
         protected bool hasNoMoreRows = false;
         private bool isDisposed;
-        private bool isClosed;
 
-        protected BaseDatabricksReader(IHiveServer2Statement statement, Schema schema, IResponse response, bool isLz4Compressed)
+        /// <summary>
+        /// Gets the statement for this reader. Subclasses can decide how to provide it.
+        /// Used for Thrift operations in DatabricksReader. Not used in CloudFetchReader.
+        /// </summary>
+        protected abstract ITracingStatement Statement { get; }
+
+        /// <summary>
+        /// Protocol-agnostic constructor.
+        /// </summary>
+        /// <param name="statement">The tracing statement (both Thrift and REST implement ITracingStatement).</param>
+        /// <param name="schema">The Arrow schema.</param>
+        /// <param name="response">The query response (nullable for REST API).</param>
+        /// <param name="isLz4Compressed">Whether results are LZ4 compressed.</param>
+        protected BaseDatabricksReader(ITracingStatement statement, Schema schema, IResponse? response, bool isLz4Compressed)
             : base(statement)
         {
             this.schema = schema;
             this.response = response;
             this.isLz4Compressed = isLz4Compressed;
-            this.statement = statement;
         }
 
         public override Schema Schema { get { return schema; } }
 
         protected override void Dispose(bool disposing)
         {
-            try
-            {
-                if (!isDisposed)
-                {
-                    if (disposing)
-                    {
-                        _ = CloseOperationAsync().Result;
-                    }
-                }
-            }
-            finally
+            if (!isDisposed)
             {
                 base.Dispose(disposing);
                 isDisposed = true;
             }
         }
 
-        /// <summary>
-        /// Closes the current operation.
-        /// </summary>
-        /// <returns>Returns true if the close operation completes successfully, false otherwise.</returns>
-        /// <exception cref="HiveServer2Exception" />
-        public async Task<bool> CloseOperationAsync()
-        {
-            try
-            {
-                if (!isClosed)
-                {
-                    _ = await HiveServer2Reader.CloseOperationAsync(this.statement, this.response);
-                    return true;
-                }
-                return false;
-            }
-            finally
-            {
-                isClosed = true;
-            }
-        }
-
         protected void ThrowIfDisposed()
         {
             if (isDisposed)
 
@@ -0,0 +1,206 @@
+/*
+* Copyright (c) 2025 ADBC Drivers Contributors
+*
+* This file has been modified from its original version, which is
+* under the Apache License:
+*
+* 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.
+*/
+
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using Microsoft.IO;
+
+namespace Apache.Arrow.Adbc.Drivers.Databricks.Reader.CloudFetch
+{
+    /// <summary>
+    /// Configuration for the CloudFetch download pipeline.
+    /// Protocol-agnostic - works with both Thrift and REST implementations.
+    /// </summary>
+    internal sealed class CloudFetchConfiguration
+    {
+        // Default values
+        internal const int DefaultParallelDownloads = 3;
+        internal const int DefaultPrefetchCount = 2;
+        internal const int DefaultMemoryBufferSizeMB = 100;
+        internal const int DefaultTimeoutMinutes = 5;
+        internal const int DefaultMaxRetries = 3;
+        internal const int DefaultRetryDelayMs = 500;
+        internal const int DefaultMaxUrlRefreshAttempts = 3;
+        internal const int DefaultUrlExpirationBufferSeconds = 60;
+
+        /// <summary>
+        /// Number of parallel downloads to perform.
+        /// </summary>
+        public int ParallelDownloads { get; set; } = DefaultParallelDownloads;
+
+        /// <summary>
+        /// Number of files to prefetch ahead of the reader.
+        /// </summary>
+        public int PrefetchCount { get; set; } = DefaultPrefetchCount;
+
+        /// <summary>
+        /// Memory buffer size limit in MB for buffered files.
+        /// </summary>
+        public int MemoryBufferSizeMB { get; set; } = DefaultMemoryBufferSizeMB;
+
+        /// <summary>
+        /// HTTP client timeout for downloads (in minutes).
+        /// </summary>
+        public int TimeoutMinutes { get; set; } = DefaultTimeoutMinutes;
+
+        /// <summary>
+        /// Maximum retry attempts for failed downloads.
+        /// </summary>
+        public int MaxRetries { get; set; } = DefaultMaxRetries;
+
+        /// <summary>
+        /// Delay between retry attempts (in milliseconds).
+        /// </summary>
+        public int RetryDelayMs { get; set; } = DefaultRetryDelayMs;
+
+        /// <summary>
+        /// Maximum attempts to refresh expired URLs.
+        /// </summary>
+        public int MaxUrlRefreshAttempts { get; set; } = DefaultMaxUrlRefreshAttempts;
+
+        /// <summary>
+        /// Buffer time before URL expiration to trigger refresh (in seconds).
+        /// </summary>
+        public int UrlExpirationBufferSeconds { get; set; } = DefaultUrlExpirationBufferSeconds;
+
+        /// <summary>
+        /// Whether the result data is LZ4 compressed.
+        /// </summary>
+        public bool IsLz4Compressed { get; set; }
+
+        /// <summary>
+        /// The Arrow schema for the results.
+        /// </summary>
+        public Schema Schema { get; set; }
+
+        /// <summary>
+        /// RecyclableMemoryStreamManager for LZ4 decompression output streams.
+        /// If not provided, a new instance will be created when needed.
+        /// For optimal memory pooling, this should be shared from the connection/database level.
+        /// </summary>
+        public RecyclableMemoryStreamManager? MemoryStreamManager { get; set; }
+
+        /// <summary>
+        /// ArrayPool for LZ4 decompression buffers.
+        /// If not provided, ArrayPool&lt;byte&gt;.Shared will be used.
+        /// For optimal memory pooling, this should be shared from the connection/database level.
+        /// </summary>
+        public ArrayPool<byte>? Lz4BufferPool { get; set; }
+
+        /// <summary>
+        /// Creates configuration from connection properties.
+        /// Works with UNIFIED properties that are shared across ALL protocols (Thrift, REST, future protocols).
+        /// Same property names (e.g., "adbc.databricks.cloudfetch.parallel_downloads") work for all protocols.
+        /// </summary>
+        /// <param name="properties">Connection properties from either Thrift or REST connection.</param>
+        /// <param name="schema">Arrow schema for the results.</param>
+        /// <param name="isLz4Compressed">Whether results are LZ4 compressed.</param>
+        /// <returns>CloudFetch configuration parsed from unified properties.</returns>
+        public static CloudFetchConfiguration FromProperties(
+            IReadOnlyDictionary<string, string> properties,
+            Schema schema,
+            bool isLz4Compressed)
+        {
+            var config = new CloudFetchConfiguration
+            {
+                Schema = schema ?? throw new ArgumentNullException(nameof(schema)),
+                IsLz4Compressed = isLz4Compressed
+            };
+
+            // Parse parallel downloads
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchParallelDownloads, out string? parallelStr))
+            {
+                if (int.TryParse(parallelStr, out int parallel) && parallel > 0)
+                    config.ParallelDownloads = parallel;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchParallelDownloads}: {parallelStr}. Expected a positive integer.");
+            }
+
+            // Parse prefetch count
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchPrefetchCount, out string? prefetchStr))
+            {
+                if (int.TryParse(prefetchStr, out int prefetch) && prefetch > 0)
+                    config.PrefetchCount = prefetch;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchPrefetchCount}: {prefetchStr}. Expected a positive integer.");
+            }
+
+            // Parse memory buffer size
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchMemoryBufferSize, out string? memoryStr))
+            {
+                if (int.TryParse(memoryStr, out int memory) && memory > 0)
+                    config.MemoryBufferSizeMB = memory;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchMemoryBufferSize}: {memoryStr}. Expected a positive integer.");
+            }
+
+            // Parse timeout
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchTimeoutMinutes, out string? timeoutStr))
+            {
+                if (int.TryParse(timeoutStr, out int timeout) && timeout > 0)
+                    config.TimeoutMinutes = timeout;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchTimeoutMinutes}: {timeoutStr}. Expected a positive integer.");
+            }
+
+            // Parse max retries
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchMaxRetries, out string? retriesStr))
+            {
+                if (int.TryParse(retriesStr, out int retries) && retries > 0)
+                    config.MaxRetries = retries;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchMaxRetries}: {retriesStr}. Expected a positive integer.");
+            }
+
+            // Parse retry delay
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchRetryDelayMs, out string? retryDelayStr))
+            {
+                if (int.TryParse(retryDelayStr, out int retryDelay) && retryDelay > 0)
+                    config.RetryDelayMs = retryDelay;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchRetryDelayMs}: {retryDelayStr}. Expected a positive integer.");
+            }
+
+            // Parse max URL refresh attempts
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchMaxUrlRefreshAttempts, out string? maxUrlRefreshStr))
+            {
+                if (int.TryParse(maxUrlRefreshStr, out int maxUrlRefresh) && maxUrlRefresh > 0)
+                    config.MaxUrlRefreshAttempts = maxUrlRefresh;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchMaxUrlRefreshAttempts}: {maxUrlRefreshStr}. Expected a positive integer.");
+            }
+
+            // Parse URL expiration buffer
+            if (properties.TryGetValue(DatabricksParameters.CloudFetchUrlExpirationBufferSeconds, out string? urlExpirationStr))
+            {
+                if (int.TryParse(urlExpirationStr, out int urlExpiration) && urlExpiration > 0)
+                    config.UrlExpirationBufferSeconds = urlExpiration;
+                else
+                    throw new ArgumentException($"Invalid {DatabricksParameters.CloudFetchUrlExpirationBufferSeconds}: {urlExpirationStr}. Expected a positive integer.");
+            }
+
+            return config;
+        }
+    }
+}