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116 lines
5.1 KiB
ReStructuredText
116 lines
5.1 KiB
ReStructuredText
.. _fts_dictionary_dialog:
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******************************
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`FTS Dictionary Dialog`:index:
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******************************
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Use the *FTS Dictionary* dialog to create a full text search dictionary. You
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can use a predefined templates or create a new dictionary with custom
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parameters.
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The *FTS Dictionary* dialog organizes the development of a FTS dictionary
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through the following dialog tabs: *General*, *Definition*, and *Options*. The
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*SQL* tab displays the SQL code generated by dialog selections.
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.. image:: images/fts_dictionary_general.png
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:alt: FTS dictionary dialog general tab
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:align: center
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Use the fields in the *General* tab to identify the dictionary:
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* Use the *Name* field to add a descriptive name for the dictionary. The name
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will be displayed in the *pgAdmin* tree control.
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* Use the drop-down listbox next to *Owner* to select the role that will own the
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FTS Dictionary.
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* Select the name of the schema in which the dictionary will reside from the
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drop-down listbox in the *Schema* field.
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* Store notes about the dictionary in the *Comment* field.
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Click the *Definition* tab to continue.
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.. image:: images/fts_dictionary_definition.png
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:alt: FTS dictionary dialog definition tab
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:align: center
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Use the field in the *Definition* tab to choose a template from the drop-down
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listbox:
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* Select *ispell* to select the Ispell template. The Ispell dictionary template
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supports morphological dictionaries, which can normalize many different
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linguistic forms of a word into the same lexeme. For example, an English
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Ispell dictionary can match all declensions and conjugations of the search
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term bank, e.g., banking, banked, banks, banks', and bank's. Ispell
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dictionaries usually recognize a limited set of words, so they should be
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followed by another broader dictionary; for example, a Snowball dictionary,
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which recognizes everything.
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* Select *simple* to select the simple template. The simple dictionary template
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operates by converting the input token to lower case and checking it against
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a file of stop words. If it is found in the file then an empty array is
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returned, causing the token to be discarded. If not, the lower-cased form of
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the word is returned as the normalized lexeme. Alternatively, the dictionary
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can be configured to report non-stop-words as unrecognized, allowing them to
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be passed on to the next dictionary in the list.
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* Select *snowball* to select the Snowball template. The Snowball dictionary
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template is based on a project by Martin Porter, inventor of the popular
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Porter's stemming algorithm for the English language. Snowball now provides
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stemming algorithms for many languages (see the Snowball site for more
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information). Each algorithm understands how to reduce common variant forms of
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words to a base, or stem, spelling within its language. A Snowball dictionary
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recognizes everything, whether or not it is able to simplify the word, so it
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should be placed at the end of the dictionary list. It is useless to have it
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before any other dictionary because a token will never pass through it to the
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next dictionary.
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* Select *synonym* to select the synonym template. This dictionary template is
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used to create dictionaries that replace a word with a synonym. Phrases are not
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supported (use the thesaurus template (Section 12.6.4) for that). A synonym
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dictionary can be used to overcome linguistic problems, for example, to prevent
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an English stemmer dictionary from reducing the word Paris to pari.
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* Select *thesaurus* to select the thesaurus template. A thesaurus dictionary
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replaces all non-preferred terms by one preferred term and, optionally,
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preserves the original terms for indexing as well. PostgreSQL's current
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implementation of the thesaurus dictionary is an extension of the synonym
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dictionary with added phrase support.
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Click the *Options* tab to continue.
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.. image:: images/fts_dictionary_options.png
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:alt: FTS dictionary dialog options tab
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:align: center
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Use the fields in the *Options* tab to provide template-specific options. Click
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the *Add* icon (+) to add an option clause:
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* Specify the name of an option in the *Option* field
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* Provide a value for the option in the *Value* field.
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Click the *Add* icon (+) to specify each additional option/value pair; to
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discard an option, click the trash icon to the left of the row and confirm
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deletion in the *Delete Row* popup.
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Click the *SQL* tab to continue.
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Your entries in the *FTS Dictionary* dialog generate a generate a SQL command.
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Use the *SQL* tab for review; revisit or switch tabs to make any changes to the
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SQL command.
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Example
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*******
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The following is an example of the sql command generated by user selections in
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the *FTS Dictionary* dialog:
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.. image:: images/fts_dictionary_sql.png
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:alt: FTS dictionary dialog sql tab
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:align: center
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The example shown demonstrates creating a custom dictionary named
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*more_stopwords* which is based on the simple template and is configured to use standard English.
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* Click the *Info* button (i) to access online help.
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* Click the *Save* button to save work.
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* Click the *Close* button to exit without saving work.
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* Click the *Reset* button to restore configuration parameters.
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