Read blob from data chunks

Giorgi · Sep 6, 2023 · 7932f5a · 7932f5a
1 parent ec81162
commit 7932f5a
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Showing 3 changed files with 37 additions and 32 deletions.
diff --git a/DuckDB.NET.Data/DuckDBDataReader.cs b/DuckDB.NET.Data/DuckDBDataReader.cs
@@ -242,8 +242,7 @@ public override string GetString(int ordinal)
                 return null;
             }
 
-            var data = NativeMethods.DataChunks.DuckDBVectorGetData(vectors[ordinal]);
-            data += currentRow * Marshal.SizeOf<DuckDBString>();
+            var data = NativeMethods.DataChunks.DuckDBVectorGetData(vectors[ordinal]) + currentRow * Marshal.SizeOf<DuckDBString>();
 
             var length = Marshal.ReadInt32(data);
 
@@ -310,8 +309,15 @@ public override int GetValues(object[] values)
 
         public override Stream GetStream(int ordinal)
         {
-            var blob = NativeMethods.Types.DuckDBValueBlob(currentResult, ordinal, currentRow);
-            return new DuckDBStream(blob);
+            var data = NativeMethods.DataChunks.DuckDBVectorGetData(vectors[ordinal]) + currentRow * Marshal.SizeOf<DuckDBString>();
+
+            var length = Marshal.ReadInt32(data);
+
+            var blobPointer = length <= InlineStringMaxLength
+                ? data + Marshal.SizeOf<int>()
+                : Marshal.ReadIntPtr(data + Marshal.SizeOf<int>() * 2);
+
+            return new DuckDBStream(blobPointer, length);
         }
 
         public override bool IsDBNull(int ordinal)

diff --git a/DuckDB.NET.Data/DuckDBStream.cs b/DuckDB.NET.Data/DuckDBStream.cs
@@ -6,12 +6,14 @@ namespace DuckDB.NET.Data;
 
 class DuckDBStream : Stream
 {
+    private readonly IntPtr data;
+
     private long position;
-    private readonly DuckDBBlob blob;
 
-    public DuckDBStream(DuckDBBlob blob)
+    public DuckDBStream(IntPtr data, long length)
     {
-        this.blob = blob;
+        this.data = data;
+        Length = length;
     }
 
     public override void Flush()
@@ -27,7 +29,7 @@ public override int Read(byte[] buffer, int offset, int count)
         {
             unchecked
             {
-                var source = position <= int.MaxValue ? IntPtr.Add(blob.Data, (int)position) : new IntPtr(blob.Data.ToInt64() + position);
+                var source = position <= int.MaxValue ? IntPtr.Add(data, (int)position) : new IntPtr(data.ToInt64() + position);
 
                 Marshal.Copy(source, buffer, offset, bytesToRead);
 
@@ -73,7 +75,7 @@ public override void Write(byte[] buffer, int offset, int count)
     public override bool CanSeek => true;
     public override bool CanWrite => false;
 
-    public override long Length => blob.Size;
+    public override long Length { get; }
 
     public override long Position
     {
@@ -83,6 +85,5 @@ public override long Position
 
     public override void Close()
     {
-        blob.Dispose();
     }
 }
diff --git a/DuckDB.NET.Test/Parameters/BlobParameterTests.cs b/DuckDB.NET.Test/Parameters/BlobParameterTests.cs
@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Numerics;
 using DuckDB.NET.Data;
 using FluentAssertions;
 using Xunit;
@@ -63,39 +62,38 @@ public void SeekTest()
         connection.Open();
 
         var command = connection.CreateCommand();
-        command.CommandText = "SELECT 'ABCDEFGH'::BLOB;";
+        var blobValue = "ABCDEFGHIJKLMNOPQR";
+        command.CommandText = $"SELECT '{blobValue}'::BLOB;";
         command.ExecuteNonQuery();
 
         var reader = command.ExecuteReader();
         reader.Read();
 
-        using (var stream = reader.GetStream(0))
+        using var stream = reader.GetStream(0);
+        stream.CanSeek.Should().Be(true);
+        using (var streamReader = new StreamReader(stream, leaveOpen: true))
         {
-            stream.CanSeek.Should().Be(true);
-            using (var streamReader = new StreamReader(stream, leaveOpen: true))
-            {
-                stream.Seek(2, SeekOrigin.Begin);
-                var text = streamReader.ReadToEnd();
-                text.Should().Be("CDEFGH");
+            stream.Seek(2, SeekOrigin.Begin);
+            var text = streamReader.ReadToEnd();
+            text.Should().Be(blobValue.Substring(2));
 
-                stream.Seek(-4, SeekOrigin.End);
-                streamReader.ReadLine().Should().Be("EFGH");
+            stream.Seek(-4, SeekOrigin.End);
+            streamReader.ReadLine().Should().Be(blobValue[^4..]);
 
-                stream.Seek(-4, SeekOrigin.End);
-                stream.Seek(2, SeekOrigin.Current);
+            stream.Seek(-4, SeekOrigin.End);
+            stream.Seek(2, SeekOrigin.Current);
 
-                streamReader.ReadLine().Should().Be("GH");
+            streamReader.ReadLine().Should().Be(blobValue[^4..][^4..][2..]);
 
-                stream.Position = 7;
-                streamReader.ReadLine().Should().Be("H");
+            stream.Position = 7;
+            streamReader.ReadLine().Should().Be(blobValue[7..]);
 
-                stream.Seek(0, SeekOrigin.Begin).Should().Be(0);
-                stream.Seek(0, SeekOrigin.End).Should().Be(stream.Length);
-                stream.Position = 5;
-                stream.Seek(0, SeekOrigin.Current).Should().Be(stream.Position);
+            stream.Seek(0, SeekOrigin.Begin).Should().Be(0);
+            stream.Seek(0, SeekOrigin.End).Should().Be(stream.Length);
+            stream.Position = 5;
+            stream.Seek(0, SeekOrigin.Current).Should().Be(stream.Position);
 
-                stream.Invoking(s => s.Seek(stream.Length+1, SeekOrigin.Current)).Should().Throw<InvalidOperationException>();
-            }
+            stream.Invoking(s => s.Seek(stream.Length+1, SeekOrigin.Current)).Should().Throw<InvalidOperationException>();
         }
     }