eZ Component: DatabaseSchema, Requirements
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*:Author:*
*:Revision:*
*:Date:*
Introduction
============
This document describes an API for direct schema manipulation. All the
functionality needed for this API is already present in the component.
Also the described use case can be solved with the current implementation, but
requires knowledge about the internal implementation of the component.
The proposed API allows to use the component for schema manipulation, but does
not require knowledge about internal implementation. It also helps to avoid
programming errors by exposing only methods instead of data structures.
Current implementation
----------------------
Database schemas can be manipulated by applying ezcDbSchemaDiff objects on the
schema. Instances of ezcDbSchemaDiff can be retrieved by loading an XML
structure or by calculating the Diff of two schemes.
The construction of an ezcDbSchemaDiff object "on the fly" seems not to be
intended by the current implementation. An example of such a creation would
be:
new ezcDbSchemaDiff( array( $name =>
new ezcDbSchemaTable( array( // type len notNull default
autoInc unsigned
'content_object_id' => new ezcDbSchemaField( 'integer', 0, TRUE, 0,
FALSE, TRUE ),
'version' => new ezcDbSchemaField( 'integer', 0, TRUE, 0,
FALSE, TRUE ),
'locale' => new ezcDbSchemaField( 'text', 255, TRUE, '',
FALSE, TRUE ),
'name' => new ezcDbSchemaField( 'text', 255, TRUE, '',
FALSE, TRUE ),
'creator_id' => new ezcDbSchemaField( 'text', 255, TRUE, '',
FALSE, TRUE ),
'created' => new ezcDbSchemaField( 'timestamp', 0, TRUE, 0,
FALSE, TRUE ),
'published' => new ezcDbSchemaField( 'timestamp', 0, FALSE, 0,
FALSE, TRUE )
), // Indexes
array(
'primary' => new ezcDbSchemaIndex( array(
'content_object_id' => new ezcDbSchemaIndexField(),
'version' => new ezcDbSchemaIndexField(),
'locale' => new ezcDbSchemaIndexField()
),
TRUE, TRUE // primary, unique
),
'name' => new ezcDbSchemaIndex( array(
'name' => new ezcDbSchemaIndexField()
),
FALSE, FALSE // primary, unique
),
)
)));
Problems with the current implementation:
- The user needs many informations: class names, constructor parameters
- Column types are specified with strings instead of constants. Therefor
typos
are not found as soon as possible.
- The interface is very verbose.
Requirements
============
The API for schema manipulation should fullfil the following requirements:
less verbosity
--------------
The API should provide default values for most options, so that the user
needs to specify only those options, which deviate from the defaults.
This is not fullfilled by the current implementation, even if the
__constructor
methods have default values. If an option at the end of the parameter list
needs
to be changed, then all other parameters must also be given.
hiding the internal implementation
----------------------------------
The user now needs to access public properties of four or five different
classes. This means, that client code becomes very sensible to changes of the
internal implementation of DatabaseSchema.
This could be avoided by providing one dedicated class ment to build a diff
object.
help to avoid errors
--------------------
By providing constants for the different options, errors can be found already
on
PHP compile time instead of execution time. Constants should be given for
example to indicate sorting order, column type and index type.
easy to use
-----------
The API should be intuitive and easy to use. It could help to name methods and
properties according to SQL syntax.
--
Thomas Koch, Software Developer
http://www.koch.ro
Young Media Concepts GmbH
Sonnenstr. 4
CH-8280 Kreuzlingen
Switzerland
Tel +41 (0)71 / 508 24 86
Fax +41 (0)71 / 560 53 89
Mobile +49 (0)170 / 753 89 16
Web www.ymc.ch
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