Table of Contents

Class YdbSqlExpressionConvertVisitor

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

Constructors

YdbSqlExpressionConvertVisitor(bool) 

public YdbSqlExpressionConvertVisitor(bool allowModify)

Parameters

allowModify bool

Fields

YdbLikeCharactersToEscape 

protected static string[] YdbLikeCharactersToEscape

Field Value

string[]

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.

CanLowerIntervalShift

Whether LowerTemporalArithmetic(SqlTemporalArithmeticExpression) can express a date shifted by an interval at all.

public override bool CanLowerIntervalShift { get; }

Property Value

bool

Remarks

Read by the member translator so a declared duration added to a date is declined while the expression is still being built, rather than reaching the builder as a node nothing can render - a refusal there has no client-side fallback left. The default follows what the base implementation needs: it spends the amount through ShiftDate(SqlIntervalUnit, ISqlExpression, ISqlExpression) at FinestDateUnit, so a provider that names no finest unit cannot lower one.

Only the declared half is declined early. A shift by a computed difference is left to be built, because start + (end - start) cancels against the difference it came from and asks the provider for nothing - refusing it here would sink a query that works everywhere.

ConcatRequiresExplicitStringCast

When true (default), ConvertConcat(SqlConcatExpression) wraps every non-string operand in an explicit CAST(... AS VARCHAR(N)) before adding it to the concat chain. Required for providers whose concat operator is + (SQL Server pre-2025, SqlCe, Access) — SQL-standard data-type precedence would otherwise try to coerce string operands to the non-string side's type. Most providers whose final concat operator is || (PostgreSQL / Oracle / SQLite / SAP HANA / DuckDB / Firebird / DB2 / Informix / SQL Server 2025+) or CONCAT(...) function (MySQL / ClickHouse) auto-coerce non-string operands and override this to false for cleaner SQL. Sybase ASE is the exception: it emits || but keeps this true, since ASE requires an explicit convert() for non-character operands under both + and ||.

protected override bool ConcatRequiresExplicitStringCast { get; }

Property Value

bool

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

SupportsNullInColumn 

protected override bool SupportsNullInColumn { get; }

Property Value

bool

Methods

ConvertConversion(SqlCastExpression)

Implements SqlCastExpression conversion.

protected override ISqlExpression ConvertConversion(SqlCastExpression cast)

Parameters

cast SqlCastExpression

Returns

ISqlExpression

ConvertDefaultValue(SqlDefaultValueExpression)

Writes the default a reader substitutes for a NULL: as its value here, and as the least value of the column's type where a provider's type cannot hold it.

public override ISqlExpression ConvertDefaultValue(SqlDefaultValueExpression expression)

Parameters

expression SqlDefaultValueExpression

The default to write.

Returns

ISqlExpression

The expression the default is written as.

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

ConvertSqlCaseExpression(SqlCaseExpression) 

protected override ISqlExpression ConvertSqlCaseExpression(SqlCaseExpression element)

Parameters

element SqlCaseExpression

Returns

ISqlExpression

ConvertSqlFunction(SqlFunction) 

public override ISqlExpression ConvertSqlFunction(SqlFunction func)

Parameters

func SqlFunction

Returns

ISqlExpression

ConvertSqlUnaryExpression(SqlUnaryExpression) 

public override ISqlExpression ConvertSqlUnaryExpression(SqlUnaryExpression element)

Parameters

element SqlUnaryExpression

Returns

ISqlExpression

CreateLikeEscapeCharacter() 

public override ISqlExpression CreateLikeEscapeCharacter()

Returns

ISqlExpression

ElapsedTicks(SqlIntervalDifferenceExpression)

Elapsed ticks from the microsecond count a YQL Interval casts to.

protected override ISqlExpression? ElapsedTicks(SqlIntervalDifferenceExpression element)

Parameters

element SqlIntervalDifferenceExpression

Returns

ISqlExpression

Remarks

Subtracting two temporal values yields an Interval, and casting one to Int64 gives the microseconds it holds - which is also the finest a YDB timestamp stores, so scaling to ticks loses nothing. The subtraction has to carry the interval type, or the cast reads as a no-op between two Int64 values and is pruned.

LowerTemporalArithmetic(SqlTemporalArithmeticExpression)

Shifts by building a YQL Interval from the tick count (microsecond resolution - YDB's own) and adding it natively.

protected override ISqlExpression? LowerTemporalArithmetic(SqlTemporalArithmeticExpression element)

Parameters

element SqlTemporalArithmeticExpression

Returns

ISqlExpression

Remarks

A DateTime is cast to Timestamp first, whatever its mapping declares: adding an interval keeps the type of the date, and a Date or a Datetime hold no time of day and no fraction of a second respectively, while a column of either mapped as a plain DateTime is not declared as one. The target is built from the CLR type, so a mapped DbType does not render the cast as the type it was meant to leave. The wide types go to Timestamp64 instead: a Timestamp would not hold their range, while a Date32 or a Datetime64 would drop the time as the narrow ones do.

The sum is optional in YQL, even over two values that cannot be absent, and an optional cannot be written to a column that is not nullable. So it is cast to its own type, which the builder unwraps wherever the value cannot be null.

VisitInSubQueryPredicate(InSubQuery) 

protected override IQueryElement VisitInSubQueryPredicate(SqlPredicate.InSubQuery predicate)

Parameters

predicate SqlPredicate.InSubQuery

Returns

IQueryElement