Manual:Searchindex table/cs

S tabulkou searchindex se pracuje při fulltextovém vyhledávání (viz ). U MySQL nužších verzí než 5.6, bylo možné fulltextové indexování jen pokud byla tabulka typu MyISAM, ale ne InnoDB. Jenže tabulka 'text' (do verze 1.4 'cur') je však typu InnoDB, protože je výhodnější z hlediska výkonu při souběžném přístupu k datům, takže aby bylo možné využít indexování na straně databáze, bylo nutné pro každou stránku vytvořit kopii. A to je důvod proč existuje tahle tabulka. Pokud používáte Postgres, tak vaše databáze tuhle tabulku nemá: informace pro fulltextové vyhledávání má v tabulce a  svůj vlastní sloupec, do kterého se zapisuje rovnou.

This table is populated when edits are saved on pages, unless is set to, or an extension that implements its own search index (like  extension) is installed. The maintenance script can be used to populate it from scratch, or  to update it for recently changed pages.

si_page
Key to.

si_title
Munged version of page title.

si_text
Munged version of the current text of the page.

Podrobnosti
Indexes for this, using en wikipedia for cardinality:  +-++--+--+-+---+-+--++--++-+ +-++--+--+-+---+-+--++--++-+ +-++--+--+-+---+-+--++--++-+
 * Table      | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
 * searchindex |         0 | si_page  |            1 | si_page     | A         |      797275 |     NULL | NULL   |      | BTREE      |         |
 * searchindex |         1 | si_title |            1 | si_title    | A         |      265758 |     NULL | NULL   |      | FULLTEXT   |         |

A common search query is of the form:

In MediaWiki version 1.4 and earlier:

Explain shows the following: +-++---+---+-+++-+ +-++---+---+-+++-+ +-++---+---+-+++-+
 * table      | type   | possible_keys                             | key           | key_len | ref        | rows   | Extra       |
 * cur        | range  | cur_id,cur_namespace,name_title_timestamp | cur_namespace |       1 | NULL       | 317499 | Using where |
 * searchindex | eq_ref | si_page                                  | si_page       |       4 | cur.cur_id |      1 | Using where |



Známé problémy
A range scan with namespaces containing a large number of records requires that a large portion of the searchindex table be loaded into RAM. This is very costly, in part because the searchindex table contains the full text of the article. A long term plan is to remove the text from the searchindex table. Temporary measures may involve adding fields to searchindex and indexing them (and using a self join to allow both that index and the fulltext index to be used) or adding a searchindex index to decrease the number of complete searchindex records which must be read to match the query.



Shrnutí schématu
+--+--+--+-+-+---+ +--+--+--+-+-+---+ +--+--+--+-+-+---+
 * Field   | Type             | Null | Key | Default | Extra |
 * si_page | int(10) unsigned | NO   | PRI | NULL    |       |
 * si_title | varchar(255)    | NO   | MUL |         |       |
 * si_text | mediumtext       | NO   | MUL | NULL    |       |

+--+-+--+-+-+---+ +--+-+--+-+-+---+ +--+-+--+-+-+---+
 * Field   | Type            | Null | Key | Default | Extra |
 * si_page | int(8) unsigned | NO   | PRI | NULL    |       |
 * si_title | varchar(255)   | NO   | MUL | NULL    |       |
 * si_text | mediumtext      | NO   | MUL | NULL    |       |

Indexy
 +-++--+--+-+---+-+--++--++-+---+ +-++--+--+-+---+-+--++--++-+---+ +-++--+--+-+---+-+--++--++-+---+
 * Table      | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
 * searchindex |         0 | si_page  |            1 | si_page     | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
 * searchindex |         1 | si_title |            1 | si_title    | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |
 * searchindex |         1 | si_text  |            1 | si_text     | NULL      |           0 |     NULL | NULL   |      | FULLTEXT   |         |               |