Fix reading numerics with big scale difference (#5851)

vonzshik · vonzshik · commit 864b9991ea85 · 2024-09-25T17:23:33.000+03:00
Fixes #5848 (cherry picked from commit 9ca526b)
diff --git a/src/Npgsql/Internal/Converters/Primitive/PgNumeric.cs b/src/Npgsql/Internal/Converters/Primitive/PgNumeric.cs
@@ -380,14 +380,24 @@ internal static decimal ToDecimal(short scale, short weight, ushort sign, Span<s
                 result += digit;
 
                 if (scaleDifference < 0)
-                    result /= UIntPowers10[-scaleDifference];
+                {
+                    // Doesn't look like we can loop even once, but just to be on a safe side
+                    while (scaleDifference < 0)
+                    {
+                        var scaleChunk = Math.Min(MaxUIntScale, -scaleDifference);
+                        result /= UIntPowers10[scaleChunk];
+                        scaleDifference += scaleChunk;
+                    }
+                }
                 else
+                {
                     while (scaleDifference > 0)
                     {
                         var scaleChunk = Math.Min(MaxUIntScale, scaleDifference);
-                        result *= UIntPowers10[scaleChunk];
+                        scaleFactor *= UIntPowers10[scaleChunk];
                         scaleDifference -= scaleChunk;
                     }
+                }
             }
 
             result *= scaleFactor;
diff --git a/test/Npgsql.Tests/Types/NumericTests.cs b/test/Npgsql.Tests/Types/NumericTests.cs
@@ -77,6 +77,8 @@ public class NumericTests : MultiplexingTestBase
 
         // Bug 2033
         new object[] { "0.0036882500000000000000000000", 0.0036882500000000000000000000M },
+        // Bug 5848
+        new object[] { "10836968.715000000000000000000000", 10836968.715000000000000000000000M },
 
         new object[] { "936490726837837729197", 936490726837837729197M },
         new object[] { "9364907268378377291970000", 9364907268378377291970000M },
