Table of Contents

Class SqlCeSqlExpressionConvertVisitor

Namespace
LinqToDB.Internal.DataProvider.SqlCe
Assembly
linq2db.dll
public class SqlCeSqlExpressionConvertVisitor : SqlExpressionConvertVisitor
Inheritance
object
SqlCeSqlExpressionConvertVisitor
Inherited Members
Extension Methods

Constructors

SqlCeSqlExpressionConvertVisitor(bool) 

public SqlCeSqlExpressionConvertVisitor(bool allowModify)

Parameters

allowModify bool

Properties

CanLowerIntervalDifference

Whether an elapsed date difference can be lowered to a value here.

public override bool CanLowerIntervalDifference { get; }

Property Value

bool

Remarks

Declared beside the lowering it describes, and read by the member translator through ITranslationContext.ProviderFlags. The translator has to ask before it builds anything, because a difference it does not build stays an ordinary .NET subtraction and is computed on materialisation - and by the time this visitor runs, the read expression is already bound to its columns, so there is no going back.

FinestDateUnit

DATEDIFF counts milliseconds, which is what a SQL CE datetime stores, so the leftover of a total is exact.

protected override SqlIntervalUnit? FinestDateUnit { get; }

Property Value

SqlIntervalUnit?

IntervalResolution

The measurement stops at the millisecond as well, so a component asked for below one is identically zero rather than merely imprecise - the count it is taken from was rounded to a coarser unit first.

public override SqlIntervalUnit IntervalResolution { get; }

Property Value

SqlIntervalUnit

Remarks

Declared for the reason SQLite declares the same limit: declining while the expression is still being built leaves the member to .NET, which holds both dates and answers exactly. A stored difference does carry a sub-millisecond part here - a datetime counts in three-and-a-third millisecond steps - so answering zero would be a wrong number rather than a coarse one.

LikeCharactersToEscape

Characters with special meaning in LIKE predicate (defined by LikeCharactersToEscape) that should be escaped to be used as matched character. Default: ["%", "_", "?", "*", "#", "[", "]"].

public override string[] LikeCharactersToEscape { get; }

Property Value

string[]

SupportsNullIf 

protected override bool SupportsNullIf { get; }

Property Value

bool

Methods

ConvertConversion(SqlCastExpression)

Implements SqlCastExpression conversion.

protected override ISqlExpression ConvertConversion(SqlCastExpression cast)

Parameters

cast SqlCastExpression

Returns

ISqlExpression

ConvertSearchStringPredicate(SearchString) 

public override ISqlPredicate ConvertSearchStringPredicate(SqlPredicate.SearchString predicate)

Parameters

predicate SqlPredicate.SearchString

Returns

ISqlPredicate

ConvertSqlBinaryExpression(SqlBinaryExpression) 

public override IQueryElement ConvertSqlBinaryExpression(SqlBinaryExpression element)

Parameters

element SqlBinaryExpression

Returns

IQueryElement

ConvertSqlFunction(SqlFunction) 

public override ISqlExpression ConvertSqlFunction(SqlFunction func)

Parameters

func SqlFunction

Returns

ISqlExpression

CountDateBoundaries(SqlIntervalUnit, ISqlExpression, ISqlExpression)

Boundary counting through DATEDIFF, which the anchor correction turns into elapsed units.

protected override ISqlExpression? CountDateBoundaries(SqlIntervalUnit unit, ISqlExpression start, ISqlExpression end)

Parameters

unit SqlIntervalUnit
start ISqlExpression
end ISqlExpression

Returns

ISqlExpression

Remarks

SQL CE has no wide form of DATEDIFF, so the count is a 32-bit integer and overflows about 24 days apart in milliseconds. Counting whole units keeps the number small for every unit a member asks for, and the fine count that fills in a fraction is only ever taken across a window shorter than one of those units. Only a total asked for in milliseconds spans the whole range in the fine unit, and there SQL CE raises an overflow rather than returning a wrapped value.

ShiftDate(SqlIntervalUnit, ISqlExpression, ISqlExpression)

Shifts a date/time value by a whole number of units - the provider's DATEADD.

protected override ISqlExpression? ShiftDate(SqlIntervalUnit unit, ISqlExpression amount, ISqlExpression date)

Parameters

unit SqlIntervalUnit
amount ISqlExpression
date ISqlExpression

Returns

ISqlExpression

Remarks

Must be exact: the anchor correction in IntervalLowering shifts by a computed count and compares the result against the original, so an approximate shift would produce an off-by-one count.

TruncateDivide(ISqlExpression, long)

The divisor carries an explicit BIGINT cast.

protected override ISqlExpression TruncateDivide(ISqlExpression value, long divisor)

Parameters

value ISqlExpression
divisor long

Returns

ISqlExpression

Remarks

SQL CE types a literal past the INT range as NUMERIC, which would make the division numeric as well - and its % rejects that type outright: "Modulo is not supported on real, float, money, and numeric data types". Naming the type keeps the division integral.

TruncateRemainder(ISqlExpression, long)

The same explicit BIGINT the division needs - SQL CE refuses a remainder on a numeric outright.

protected override ISqlExpression TruncateRemainder(ISqlExpression value, long divisor)

Parameters

value ISqlExpression
divisor long

Returns

ISqlExpression