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Add function mapping for Ticks to sqlserver #35465

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Add function mapping for Ticks to sqlserver #35465

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5fe7052
Add function mapping for Ticks to sqlserver
sharetek-wangkexin Jan 14, 2025
a0dee3e
Merge branch 'dotnet:main' into sqlserver-functions
z505985755 Feb 6, 2025
3f1f906
Modify the assertion of Select_datetime_Ticks_component
sharetek-wangkexin Feb 7, 2025
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35 changes: 35 additions & 0 deletions src/EFCore.SqlServer/Query/Internal/Translators/SqlServerDateTimeMemberTranslator.cs
View file
Original file line number Diff line number Diff line change
@@ -48,6 +48,41 @@ public class SqlServerDateTimeMemberTranslator(
nameof(DateTime.Millisecond) => DatePart("millisecond"),
nameof(DateTime.Microsecond) => sqlExpressionFactory.Modulo(DatePart("microsecond"), sqlExpressionFactory.Constant(1000)),
nameof(DateTime.Nanosecond) => sqlExpressionFactory.Modulo(DatePart("nanosecond"), sqlExpressionFactory.Constant(1000)),
//Use datediff to get the minute difference of 0001-01-01 00:00:00.0, then multiply it by the scale of each minute,
//and then get the scale of seconds, milliseconds, microseconds, and nanoseconds respectively, and finally add them together.
//The nanoseconds obtained by DATEPART include milliseconds and microseconds.
nameof(DateTime.Ticks)
=> sqlExpressionFactory.Add(
sqlExpressionFactory.Multiply(
sqlExpressionFactory.Function(
"DATEDIFF",
arguments: new[]
{
sqlExpressionFactory.Fragment("minute"),
sqlExpressionFactory.Constant("0001-01-01T00:00:00.0"),
instance!
},
nullable: true,
argumentsPropagateNullability: new[] { false, false, true },
typeof(long)),
sqlExpressionFactory.Constant(600000000)),
sqlExpressionFactory.Add(
sqlExpressionFactory.Multiply(
sqlExpressionFactory.Function(
"DATEPART",
arguments: new[] { sqlExpressionFactory.Fragment("second"), instance! },
nullable: true,
argumentsPropagateNullability: Statics.FalseTrue,
typeof(int)),
sqlExpressionFactory.Constant(10000000)),
sqlExpressionFactory.Divide(
sqlExpressionFactory.Function(
"DATEPART",
arguments: new[] { sqlExpressionFactory.Fragment("nanosecond"), instance! },
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Am noting that this duplicate instance twice in the translation; if that's a complicated expression (e.g. with a subquery), that's bad for performance - for those cases, we tend to do the translation only if we know that's it's a simple column/parameter, rather than a complex expression. I also saw a brief discussion over multiple translation possibilities (possibly some not supported in older SQL Server), I'd lean towards one that doesn't duplicate expressions - even if it's not supported across all versions/variants - rather than one that's supported everything but duplicates.

(regardless, this is missing test coverage)

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If use datediff_big to calculate the microsecond difference and then multiply it by 10, may lose one digit of precision because the datetime2 data type supports up to 7 decimal places. If use datediff_big to calculate the nanosecond difference and then divide it by 100, it will cause an overflow.
So, I can't think of a solution without using complex expressions.What are you suggesting?

nullable: true,
argumentsPropagateNullability: Statics.FalseTrue,
typeof(int)),
sqlExpressionFactory.Constant(100)))),

nameof(DateTime.Date)
=> sqlExpressionFactory.Function(
2 changes: 1 addition & 1 deletion test/EFCore.SqlServer.FunctionalTests/Query/NorthwindSelectQuerySqlServerTest.cs
View file
Original file line number Diff line number Diff line change
@@ -2532,7 +2532,7 @@ public override async Task Select_datetime_Ticks_component(bool async)

AssertSql(
"""
SELECT [o].[OrderDate]
SELECT DATEDIFF(minute, N'0001-01-01T00:00:00.0', [o].[OrderDate]) * CAST(600000000 AS bigint) + DATEPART(second, [o].[OrderDate]) * CAST(10000000 AS bigint) + DATEPART(nanosecond, [o].[OrderDate]) / CAST(100 AS bigint)
FROM [Orders] AS [o]
""");
}