com.pervasive.datarush.types

Class FieldRemappings

java.lang.Object

com.pervasive.datarush.types.FieldRemappings

public class FieldRemappings
extends Object

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FieldRemappings.Directive A mapping directive to be applied to a source field.

Constructor Summary

Constructors

Constructor and Description
FieldRemappings()

Method Summary

Modifier and Type	Method and Description
static FieldRemappings.Directive	drop(String name) Declares a source field is to be omitted from the result.
static FieldRemappings.Directive	keep(String name) Declares a source field is to be preserved in the result, keeping the same name.
static FieldRemappings.Directive	map(String from, String to) Defines a name mapping from a source to a target field.
static FieldRemapping	patternRename(String format, String... excludedFields) Defines a simple pattern-based renaming fields of a record schema.
static FieldRemapping	rename(FieldRemappings.Directive... directives) Defines a transformation renaming fields of a record schema.
static FieldRemapping	renameAndDrop(FieldRemappings.Directive... directives) Defines a transformation renaming fields of a record schema, dropping source fields without an explicit directive.
static FieldRemapping	reorder(FieldRemappings.Directive... directives) Defines a transformation reordering and possibly renaming fields of a record schema.
static FieldRemapping	reorderAndDrop(FieldRemappings.Directive... directives) Defines a transformation reordering and possibly renaming fields of a record schema, dropping source fields without an explicit directive.

Methods inherited from class java.lang.Object

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

Constructor Detail

FieldRemappings

public FieldRemappings()

Method Detail

drop

public static FieldRemappings.Directive drop(String name)

Declares a source field is to be omitted from the result.

This is useful is forcibly removing fields from the source when they otherwise would be kept, for example when using rename(Directive...) or reorder(Directive...).

If the only actions being done are the dropping of unwanted fields, consider using one of SelectFields, RetainFields, or RemoveFields.

Parameters:

name - the name of the source field to drop from the target

Returns:

the declared directive

keep

public static FieldRemappings.Directive keep(String name)

Declares a source field is to be preserved in the result, keeping the same name.

This is useful if renaming is not desired, but a mapping is needed to produce desired ordering or preserve a field in a type mapping.

Parameters:

name - the name of the source field to keep in the target

Returns:

the declared directive

map

public static FieldRemappings.Directive map(String from,
                                            String to)

Defines a name mapping from a source to a target field.

Parameters:

from - the name of the field in the source

to - the name of the field in the target

Returns:

the defined mapping

patternRename

public static FieldRemapping patternRename(String format,
                                           String... excludedFields)

Defines a simple pattern-based renaming fields of a record schema. The relative order of fields is unchanged. For all fields not explicitly excluded, a supplied formatting pattern is applied to produce the new name.

Parameters:

format - a pattern for renaming of fields. This is in the syntax supported by MessageFormat. There will be exactly one argument to format - the name of the field.

excludedFields - names of fields which should not be be renamed.

Returns:

a transform applying the specified pattern-based renaming

rename

public static FieldRemapping rename(FieldRemappings.Directive... directives)

Defines a transformation renaming fields of a record schema. The relative order of fields is unchanged.

For example, if the source schema is {"a", "b", "c"} and the directives [ "c"->"Z", "a"->"X" ] are applied, the result is { "X", "b", "Z" }.

Note that in this context, a keep(java.lang.String) directive is a no-op.

Parameters:

directives - the field mapping operations to apply.

Returns:

a transform applying the supplied directives

renameAndDrop

public static FieldRemapping renameAndDrop(FieldRemappings.Directive... directives)

Defines a transformation renaming fields of a record schema, dropping source fields without an explicit directive. The relative order of fields is unchanged.

For example, if the source schema is {"a", "b", "c"} and the directives [ "c"->"Z", "a"->"X" ] are applied, the result is { "X", "Z" }.

Note that in this context, a drop(java.lang.String) directive is a no-op. Further, this transformation is equivalent to combining a rename operation with a RetainFields.

Parameters:

directives - the field mapping operations to apply.

Returns:

a transform applying the supplied directives

reorder

public static FieldRemapping reorder(FieldRemappings.Directive... directives)

Defines a transformation reordering and possibly renaming fields of a record schema. Source fields can be referenced multiple times (using different target names), producing "aliases" of the same field in the result. The order of fields in the result is determined as described below:

• Source fields specified in the directives will appear in the same order they are referenced in the directive list.
• Source fields not referenced by any directive will appear after fields specified in the directives, in the same relative order as in the source.

For example, if the source schema is {"a", "b", "c"} and the directives [ "c"->"Z", "a"->"X" ] are applied, the result is { "Z", "X", "b" }.

Unlike rename(Directive...), a keep(java.lang.String) directive does exhibit an effect, controlling the ordering of a field in the result.

Parameters:

directives - the field mapping operations to apply.

Returns:

a transform applying the supplied directives

reorderAndDrop

public static FieldRemapping reorderAndDrop(FieldRemappings.Directive... directives)

Defines a transformation reordering and possibly renaming fields of a record schema, dropping source fields without an explicit directive. Source fields can be referenced multiple times (using different target names), producing "aliases" of the same field in the result. The order of fields in the result is the same order they are referenced in the directive list.

As an example, if the source schema is {"a", "b", "c"} and the directives [ "c"->"Z", "a"->"X" ] are applied, the result is { "Z", "X" }.

Note that in this context, a drop(java.lang.String) directive is a no-op. Further, this transformation is equivalent to combining a renaming operation with a SelectFields.

Parameters:

directives - the field mapping operations to apply.

Returns:

a transform applying the supplied directives