From 945a4cba6522f8c57a7a56884337b980043b9a23 Mon Sep 17 00:00:00 2001
From: Nikita Kazmin <vonzshik@gmail.com>
Date: Mon, 22 Dec 2025 11:21:17 +0300
Subject: [PATCH 1/2] Fix reading numerics as BigInteger

---
 .../Converters/Primitive/NumericConverters.cs      |  4 ++--
 test/Npgsql.Tests/Types/NumericTests.cs            | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs b/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs
index c14a00b608..ce74deaa2f 100644
--- a/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs
+++ b/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs
@@ -166,11 +166,11 @@ public static async ValueTask<PgNumeric> ReadAsync(PgReader reader, ArraySegment
         var sign = reader.ReadInt16();
         var scale = reader.ReadInt16();
         var array = digits.Array!;
-        for (var i = digits.Offset; i < array.Length; i++)
+        for (var i = 0; i < digits.Count; i++)
         {
             if (reader.ShouldBuffer(sizeof(short)))
                 await reader.BufferAsync(sizeof(short), cancellationToken).ConfigureAwait(false);
-            array[i] = reader.ReadInt16();
+            array[i + digits.Offset] = reader.ReadInt16();
         }
 
         return new PgNumeric.Builder(digits, weight, sign, scale).Build();
diff --git a/test/Npgsql.Tests/Types/NumericTests.cs b/test/Npgsql.Tests/Types/NumericTests.cs
index 20eed3fa04..439d651559 100644
--- a/test/Npgsql.Tests/Types/NumericTests.cs
+++ b/test/Npgsql.Tests/Types/NumericTests.cs
@@ -212,4 +212,18 @@ public async Task NumericZero_WithScale()
 
         Assert.That(value.Scale, Is.EqualTo(2));
     }
+
+    [Test, IssueLink("https://github.com/npgsql/npgsql/issues/6383")]
+    public async Task Read_Many_Numerics_As_BigInteger([Values(CommandBehavior.Default, CommandBehavior.SequentialAccess)] CommandBehavior behavior)
+    {
+        await using var conn = await OpenConnectionAsync();
+        await using var cmd = conn.CreateCommand();
+        cmd.CommandText = "SELECT 1234567890::numeric FROM generate_series(1, 8000)";
+
+        await using var reader = await cmd.ExecuteReaderAsync(behavior);
+        while (await reader.ReadAsync())
+        {
+            Assert.DoesNotThrowAsync(async () => await reader.GetFieldValueAsync<BigInteger>(0));
+        }
+    }
 }

From 826ba87e12267ac8e7fb9065808c22ff79845bb1 Mon Sep 17 00:00:00 2001
From: Nikita Kazmin <vonzshik@gmail.com>
Date: Tue, 23 Dec 2025 10:59:09 +0300
Subject: [PATCH 2/2] Review

---
 src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs b/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs
index ce74deaa2f..714d3c49d4 100644
--- a/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs
+++ b/src/Npgsql/Internal/Converters/Primitive/NumericConverters.cs
@@ -166,11 +166,11 @@ public static async ValueTask<PgNumeric> ReadAsync(PgReader reader, ArraySegment
         var sign = reader.ReadInt16();
         var scale = reader.ReadInt16();
         var array = digits.Array!;
-        for (var i = 0; i < digits.Count; i++)
+        for (var i = digits.Offset; i < digits.Offset + digits.Count; i++)
         {
             if (reader.ShouldBuffer(sizeof(short)))
                 await reader.BufferAsync(sizeof(short), cancellationToken).ConfigureAwait(false);
-            array[i + digits.Offset] = reader.ReadInt16();
+            array[i] = reader.ReadInt16();
         }
 
         return new PgNumeric.Builder(digits, weight, sign, scale).Build();