Numeric casts round instead of truncating, `(byte)` casts don't wrap, and `BigInteger` division isn't integer division

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70/100
Issue 類型
缺陷
描述清晰度
描述清楚
活躍度
活躍
技術堆疊
csharp, postgresql
領域
database

研究方向

Start in NpgsqlQuerySqlGenerator.cs (L603-626) where integer casts render as ::int; switch to trunc(x)::int to match .NET truncation. Then fix NpgsqlConvertTranslator.cs L36 and NpgsqlBigIntegerTypeMapping.cs L30 (use div for division). Run the issue's repro to confirm all four LINQ queries return identical .NET and database results.

由索引模型根據 Issue 內容生成。

描述

Environment
PostgreSQL 18.6 (postgres:18), session TimeZone Etc/UTC
.NET 10 runtime 10.0.11, Npgsql.EntityFrameworkCore.PostgreSQL 10.0.3, EF Core 10.0.4
.NET 11 runtime 11.0.0-rc.2, Npgsql.EntityFrameworkCore.PostgreSQL 11.0.0-rc.2, EF Core 11.0.0-rc.2
Also Npgsql 10.0.3 on both lines, macOS arm64

Both lines print the same output. main at 150011d has the same code.

LINQ Row .NET PostgreSQL SQL
(int)r.Decimal 2.7m 2 3 r."Decimal"::int
(long)r.Double 2.7 2 3 r."Double"::bigint
(byte)r.Int == 249 −7 match no match r."Int"::smallint = 249
r.Big / r.Big2 == 3 7 / 2 match no match r."Big" / r."Big2" = 3
Repro 
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using System.Numerics;

await using var context = new TestContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

context.Rows.Add(new Row { Decimal = 2.7m, Double = 2.7, Int = -7, Big = 7, Big2 = 2 });
await context.SaveChangesAsync();
var row = await context.Rows.AsNoTracking().SingleAsync();

// 1. C# casts truncate toward zero; ::int rounds
Console.WriteLine($"(int)2.7m: .NET {(int)row.Decimal}, database {await context.Rows.Select(r => (int)r.Decimal).SingleAsync()}");
Console.WriteLine($"(long)2.7: .NET {(long)row.Double}, database {await context.Rows.Select(r => (long)r.Double).SingleAsync()}");

// 2. An unchecked byte cast wraps; ::smallint keeps -7
Console.WriteLine($"(byte)-7 == 249: .NET {((byte)row.Int == 249 ? 1 : 0)}, database {await context.Rows.CountAsync(r => (byte)r.Int == 249)}");

// 3. BigInteger division is integer division
Console.WriteLine($"Big / Big2 == 3 (7 / 2): .NET {(row.Big / row.Big2 == 3 ? 1 : 0)}, database {await context.Rows.CountAsync(r => r.Big / r.Big2 == 3)}");

public class TestContext : DbContext
{
    public DbSet<Row> Rows => Set<Row>();

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseNpgsql(Environment.GetEnvironmentVariable("Test__Npgsql__DefaultConnection"), o => o.UseNodaTime())
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();
}

public class Row
{
    public int Id { get; set; }
    public decimal Decimal { get; set; }
    public double Double { get; set; }
    public int Int { get; set; }
    public BigInteger Big { get; set; }
    public BigInteger Big2 { get; set; }
}

Output, the same on both lines:

(int)2.7m: .NET 2, database 3
(long)2.7: .NET 2, database 3
(byte)-7 == 249: .NET 1, database 0
Big / Big2 == 3 (7 / 2): .NET 1, database 0
  • Casts. C# casts from decimal, double and float to an integer type truncate toward zero. PostgreSQL's casts round: half away from zero for numeric, half to even for float8. SQL Server's CAST truncates, so this is specific to this provider. The cast is rendered as ::int (NpgsqlQuerySqlGenerator.cs#L603-L626); trunc(x)::int would match .NET. Convert.ToInt32(decimal) goes the same way (NpgsqlConvertTranslator.cs#L36) and rounds half away from zero, where .NET rounds half to even.
  • byte maps to smallint, so an unchecked (byte) cast keeps −7 instead of wrapping to 249.
  • BigInteger maps to numeric (NpgsqlBigIntegerTypeMapping.cs#L30), so / is numeric division (3.5). div(a, b) matches BigInteger's truncating division.
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