Class TransformedSqlColumn

java.lang.Object

com.randomnoun.common.jexl.sql.SqlColumn

com.randomnoun.common.jexl.sql.TransformedSqlColumn

public abstract class TransformedSqlColumn
extends SqlColumn

An SQL column which represents a transformed value ( the value in the expression is not the stored value ).

Examples of TransformedSqlColumns:

• enum values ( 1-char in database exposed as enum strings )
• yes/no values ( 'Y'/'N' in database exposed as booleans )
• api-prefixed values ( 1234 in database exposed as "obj-1234" )

If the transformation is reversible, we can convert some expressions to use the raw column which can then leverage indexes on that column.

Field Summary

Fields inherited from class SqlColumn

ARRAY, BIGINT, BINARY, BIT, BLOB, BOOLEAN, CHAR, CLOB, DATALINK, dataType, DATE, DATEVALUE, DECIMAL, DISTINCT, DOUBLE, FIXEDDATEVALUE, FIXEDTIMEVALUE, FLOAT, INTEGER, JAVA_OBJECT, LONGVARBINARY, LONGVARCHAR, name, NULL, NUMERIC, OTHER, REAL, REF, SMALLINT, STRUCT, table, TIME, TIMESTAMP, TIMEVALUE, TINYINT, VARBINARY, VARCHAR

Constructor Summary

Constructors

Constructor	Description
TransformedSqlColumn(String name, String table, int dataType)

Method Summary

Modifier and Type	Method	Description
abstract SqlColumn	getSourceSqlColumn()	The source column
abstract boolean	isNullPreserved()	If true, we can perform null checks on the source column instead of the transformed value
abstract boolean	isReversableComparison()	If true, we can reverse transformations for comparison operations; we can only do this if transformations preserve ordering
abstract boolean	isReversableEquals()	If true, we can reverse transformations for equals and not-equals comparisons
abstract Object	reverseTransformLiteral(Object value)	Reverse the transformation, i.e. convert a user-supplied value back into a database value.

Methods inherited from class SqlColumn

getDataType, getFullName, getName, getTable, toString

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

TransformedSqlColumn

public TransformedSqlColumn(String name,
 String table,
 int dataType)

Method Details

isNullPreserved

public abstract boolean isNullPreserved()

If true, we can perform null checks on the source column instead of the transformed value

isReversableEquals

public abstract boolean isReversableEquals()

If true, we can reverse transformations for equals and not-equals comparisons

isReversableComparison

public abstract boolean isReversableComparison()

If true, we can reverse transformations for comparison operations; we can only do this if transformations preserve ordering

getSourceSqlColumn

public abstract SqlColumn getSourceSqlColumn()

The source column

reverseTransformLiteral

public abstract Object reverseTransformLiteral(Object value)
                                        throws CannotReverseTransformationException

Reverse the transformation, i.e. convert a user-supplied value back into a database value. The user-supplied value must be a literal (String, Boolean, Long etc), not an expression.

Parameters:

value - literal value in expression

Throws:

CannotReverseTransformationException