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Class Expression

This class manage the creation of Expressions. These can be Predicate, Artithmetich and String expressions. Also aggregations can be built using an instance of the Expression class

There are differnet kind of expression as constant values, field values, old field values (used in upsert definitios addUpsertDefition(Expression[])) and aggregations aggr(Expression.Op, Expression)

Every expression can be combined to create other Expresssions by using unary, binary and ternary operatos Expression.Op.

Group by scan with having the first field as the field #3, second as the maximun value for field #9
        Expression[] groupbyexprs = new Expression[2];
        groupbyexprs[0] = Expression.fieldStr(3);
        groupbyexprs[1] = Expression.aggr(Expression.Op.KVMAX, Expression.fieldFloat(9));
    Scan scan = table.scan(new ScanProperties(table).groupBy(groupbyexprs), 0);</code></pre>
Inheritance
System.Object
Expression
Implements
System.IDisposable
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
System.Object.ToString()
Namespace: lxapi
Assembly: lxapi.dll
Syntax
public class Expression : IDisposable

Constructors

Expression(Decimal)

Constant decimal expression

Declaration
public Expression(Decimal val)
Parameters
Type Name Description
Decimal val

value

Expression(Expression.Op, Expression)

Unary expression

Declaration
public Expression(Expression.Op op, Expression op1)
Parameters
Type Name Description
Expression.Op op

unary operator Expression.Op

Expression op1

expr1

Expression(Expression.Op, Expression, Expression)

Binary expression

Declaration
public Expression(Expression.Op op, Expression op1, Expression op2)
Parameters
Type Name Description
Expression.Op op

Binary operator Expression.Op

Expression op1

expr1

Expression op2

expr2

Expression(Expression.Op, Expression, Expression, Expression)

Ternary expression

Declaration
public Expression(Expression.Op op, Expression op1, Expression op2, Expression op3)
Parameters
Type Name Description
Expression.Op op

Ternary operator Expression.Op

Expression op1

expr1

Expression op2

expr2

Expression op3

expr3

Expression(Byte[])

Constant byte array expression

Declaration
public Expression(byte[] val)
Parameters
Type Name Description
System.Byte[] val

value

Expression(Double)

Constant double expression

Declaration
public Expression(double val)
Parameters
Type Name Description
System.Double val

value

Expression(Int64)

Constant long expression

Declaration
public Expression(long val)
Parameters
Type Name Description
System.Int64 val

value

Expression(String)

Constant string expression

Declaration
public Expression(string val)
Parameters
Type Name Description
System.String val

value

Methods

aggr(Expression.Op, Expression)

Aggregate expression.

 Expression[] groupbyexprs = new Expression[3];
 groupbyexprs[0] = Expression.fieldStr(2); // group by third column 
 groupbyexprs[1] = Expression.aggr(Expression.Op.KVADD, Expression(1)); // count over the third column
 groupbyexprs[2] = Expression.aggr(Expression.Op.KVMAX, Expression.fieldFloat(1)); // max second column for the same third column
Declaration
public static Expression aggr(Expression.Op op, Expression op1)
Parameters
Type Name Description
Expression.Op op

unary operator Expression.Op

Expression op1
Returns
Type Description
Expression

Dispose()

Dispose

Declaration
public void Dispose()

Dispose(Boolean)

Release expression Handle

Declaration
protected virtual void Dispose(bool disposing)
Parameters
Type Name Description
System.Boolean disposing

fieldBytes(Int32)

Byte array Column expression

Declaration
public static Expression fieldBytes(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

fieldDecimal(Int32)

Decimal Column expression

Declaration
public static Expression fieldDecimal(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

fieldFloat(Int32)

Float Column expression

Declaration
public static Expression fieldFloat(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

fieldInt(Int32)

Integer Column expression

Declaration
public static Expression fieldInt(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

fieldStr(Int32)

String Column expression

Declaration
public static Expression fieldStr(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

Finalize()

Destructor

Declaration
protected void Finalize()

nullBytes()

Null byte array expression

Declaration
public static Expression nullBytes()
Returns
Type Description
Expression

nullDecimal()

Null Decimal expression

Declaration
public static Expression nullDecimal()
Returns
Type Description
Expression

nullFloat()

Null float expression

Declaration
public static Expression nullFloat()
Returns
Type Description
Expression

nullInt()

Null integer expression

Declaration
public static Expression nullInt()
Returns
Type Description
Expression

nullStr()

Null string expression

Declaration
public static Expression nullStr()
Returns
Type Description
Expression

oldFieldBytes(Int32)

Byte array Column old value expression. addUpsertDefition(Expression[])

Declaration
public static Expression oldFieldBytes(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

oldFieldDecimal(Int32)

Decimal Column old value expression. addUpsertDefition(Expression[])

Declaration
public static Expression oldFieldDecimal(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

oldFieldFloat(Int32)

Float Column old value expression. addUpsertDefition(Expression[])

Declaration
public static Expression oldFieldFloat(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

oldFieldInt(Int32)

Integer Column old value expression. addUpsertDefition(Expression[])

Declaration
public static Expression oldFieldInt(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

oldFieldStr(Int32)

String Column old value expression. addUpsertDefition(Expression[])

Declaration
public static Expression oldFieldStr(int fno)
Parameters
Type Name Description
System.Int32 fno

column position

Returns
Type Description
Expression

op(Expression.Op)

Apply unary operator to expression

Declaration
public Expression op(Expression.Op op)
Parameters
Type Name Description
Expression.Op op

unary operator Expression.Op

Returns
Type Description
Expression

New expression

op(Expression.Op, Expression)

Apply binary operator to expression

Declaration
public Expression op(Expression.Op op, Expression op2)
Parameters
Type Name Description
Expression.Op op

binary operator Expression.Op

Expression op2

expr2

Returns
Type Description
Expression

New expression

op(Expression.Op, Expression, Expression)

Apply ternary operator to expression

Declaration
public Expression op(Expression.Op op, Expression op2, Expression op3)
Parameters
Type Name Description
Expression.Op op

ternary operator Expression.Op

Expression op2

expr2

Expression op3

expr3

Returns
Type Description
Expression

New expression

Implements

System.IDisposable
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