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158 lines
7.8 KiB
158 lines
7.8 KiB
.. _transformations: |
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Transformations |
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=============== |
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.. note:: |
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You need to have configured the :ref:`linked-tables` to use the transformations |
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feature. |
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.. _transformationsintro: |
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Introduction |
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++++++++++++ |
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To enable transformations, you have to set up the ``column_info`` |
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table and the proper directives. Please see the :ref:`config` on how to do so. |
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phpMyAdmin has two different types of transformations: browser display |
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transformations, which affect only how the data is shown when browsing |
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through phpMyAdmin; and input transformations, which affect a value |
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prior to being inserted through phpMyAdmin. |
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You can apply different transformations to the contents of each |
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column. Each transformation has options to define how it will affect the |
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stored data. |
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Say you have a column ``filename`` which contains a filename. Normally |
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you would see in phpMyAdmin only this filename. Using display transformations |
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you can transform that filename into a HTML link, so you can click |
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inside of the phpMyAdmin structure on the column's link and will see |
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the file displayed in a new browser window. Using transformation |
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options you can also specify strings to append/prepend to a string or |
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the format you want the output stored in. |
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For a general overview of all available transformations and their |
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options, you can either go to the ``Change`` link for an existing column |
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or from the dialog to create a new column, in either case there is a link |
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on that column structure page for "Browser display transformation" and |
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"Input transformation" which will show more information about each |
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transformation that is available on your system. |
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For a tutorial on how to effectively use transformations, see our |
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`Link section <https://www.phpmyadmin.net/docs/>`_ on the |
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official phpMyAdmin homepage. |
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.. _transformationshowto: |
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Usage |
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+++++ |
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Go to the table structure page (reached by clicking on |
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the 'Structure' link for a table). There click on "Change" (or the change |
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icon) and there you will see the five transformation--related fields at the end of the line. |
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They are called ':term:`Media type`', 'Browser transformation' and |
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'Transformation options'. |
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* The field ':term:`Media type`' is a drop-down field. Select the :term:`Media type` that |
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corresponds to the column's contents. Please note that many transformations |
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are inactive until a :term:`Media type` is selected. |
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* The field 'Browser display transformation' is a drop-down field. You can |
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choose from a hopefully growing amount of pre-defined transformations. |
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See below for information on how to build your own transformation. |
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There are global transformations and mimetype-bound transformations. |
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Global transformations can be used for any mimetype. They will take |
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the mimetype, if necessary, into regard. Mimetype-bound |
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transformations usually only operate on a certain mimetype. There are |
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transformations which operate on the main mimetype (like 'image'), |
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which will most likely take the subtype into regard, and those who |
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only operate on a specific subtype (like 'image/jpeg'). You can use |
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transformations on mimetypes for which the function was not defined |
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for. There is no security check for you selected the right |
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transformation, so take care of what the output will be like. |
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* The field 'Browser display transformation options' is a free-type textfield. You have |
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to enter transform-function specific options here. Usually the |
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transforms can operate with default options, but it is generally a |
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good idea to look up the overview to see which options are necessary. |
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Much like the ENUM/SET-Fields, you have to split up several options |
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using the format 'a','b','c',...(NOTE THE MISSING BLANKS). This is |
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because internally the options will be parsed as an array, leaving the |
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first value the first element in the array, and so forth. If you want |
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to specify a MIME character set you can define it in the |
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transformation\_options. You have to put that outside of the pre- |
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defined options of the specific mime-transform, as the last value of |
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the set. Use the format "'; charset=XXX'". If you use a transform, for |
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which you can specify 2 options and you want to append a character |
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set, enter "'first parameter','second parameter','charset=us-ascii'". |
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You can, however use the defaults for the parameters: "'','','charset |
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=us-ascii'". The default options can be configured using |
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:config:option:`$cfg['DefaultTransformations']`. |
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* 'Input transformation' is another drop-down menu that corresponds exactly |
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with the instructions above for "Browser display transformation" except |
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these these affect the data before insertion in to the database. These are |
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most commonly used to either provide a specialized editor (for example, using |
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the phpMyAdmin SQL editor interface) or selector (such as for uploading an image). |
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It's also possible to manipulate the data such as converting an IPv4 address to binary |
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or parsing it through a regular expression. |
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* Finally, 'Input transformation options' is the equivalent of the "Browser display |
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transformation options" section above and is where optional and required parameters are entered. |
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.. _transformationsfiles: |
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File structure |
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++++++++++++++ |
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All specific transformations for mimetypes are defined through class |
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files in the directory :file:`libraries/classes/Plugins/Transformations/`. Each of |
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them extends a certain transformation abstract class declared in |
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:file:`libraries/classes/Plugins/Transformations/Abs`. |
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They are stored in files to ease customization and to allow easy adding of |
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new or custom transformations. |
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Because the user cannot enter their own mimetypes, it is kept certain that |
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the transformations will always work. It makes no sense to apply a |
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transformation to a mimetype the transform-function doesn't know to |
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handle. |
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There is a file called :file:`libraries/classes/Plugins/Transformations.php` that provides some |
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basic functions which can be included by any other transform function. |
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The file name convention is ``[Mimetype]_[Subtype]_[Transformation |
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Name].php``, while the abstract class that it extends has the |
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name ``[Transformation Name]TransformationsPlugin``. All of the |
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methods that have to be implemented by a transformations plug-in are: |
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#. getMIMEType() and getMIMESubtype() in the main class; |
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#. getName(), getInfo() and applyTransformation() in the abstract class |
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it extends. |
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The getMIMEType(), getMIMESubtype() and getName() methods return the |
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name of the MIME type, MIME Subtype and transformation accordingly. |
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getInfo() returns the transformation's description and possible |
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options it may receive and applyTransformation() is the method that |
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does the actual work of the transformation plug-in. |
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Please see the :file:`libraries/classes/Plugins/Transformations/TEMPLATE` and |
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:file:`libraries/classes/Plugins/Transformations/TEMPLATE\_ABSTRACT` files for adding |
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your own transformation plug-in. You can also generate a new |
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transformation plug-in (with or without the abstract transformation |
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class), by using |
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:file:`scripts/transformations_generator_plugin.sh` or |
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:file:`scripts/transformations_generator_main_class.sh`. |
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The applyTransformation() method always gets passed three variables: |
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#. **$buffer** - Contains the text inside of the column. This is the |
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text, you want to transform. |
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#. **$options** - Contains any user-passed options to a transform |
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function as an array. |
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#. **$meta** - Contains an object with information about your column. The |
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data is drawn from the output of the `mysql\_fetch\_field() |
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<https://www.php.net/mysql_fetch_field>`_ function. This means, all |
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object properties described on the `manual page |
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<https://www.php.net/mysql_fetch_field>`_ are available in this |
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variable and can be used to transform a column accordingly to |
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unsigned/zerofill/not\_null/... properties. The $meta->mimetype |
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variable contains the original :term:`Media type` of the column (i.e. |
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'text/plain', 'image/jpeg' etc.)
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