12.5. 解析器 · PostgreSQL 中文文檔 9.3

# 12.5\. 解析器文本搜索分析器負責分離原文檔文本為_標記_并且標識每個記號的類型，這里可能的類型集由解析器本身定義。注意一個解析器并不修改文本—它只是確定合理的單詞邊界。因為這個限制范圍，為特定應用定制的分析器比自定義字典需要的更少。目前PostgreSQL提供了只有一個內置的解析器，這已被用于一個廣泛的應用中。內置分析器命名`pg_catalog.default`。它識別23種標記類型，顯示在[Table 12-1](#calibre_link-1145)中。 **Table 12-1\. 缺省分析器的標記類型** | Alias | Description | Example | | --- | --- | --- | | `asciiword` | Word, all ASCII letters | `elephant` | | `word` | Word, all letters | `ma?ana` | | `numword` | Word, letters and digits | `beta1` | | `asciihword` | Hyphenated word, all ASCII | `up-to-date` | | `hword` | Hyphenated word, all letters | `lógico-matemática` | | `numhword` | Hyphenated word, letters and digits | `postgresql-beta1` | | `hword_asciipart` | Hyphenated word part, all ASCII | `postgresql` in the context `postgresql-beta1` | | `hword_part` | Hyphenated word part, all letters | `lógico` or `matemática` in the context `lógico-matemática` | | `hword_numpart` | Hyphenated word part, letters and digits | `beta1` in the context `postgresql-beta1` | | `email` | Email address | `foo@example.com` | | `protocol` | Protocol head | `http://` | | `url` | URL | `example.com/stuff/index.html` | | `host` | Host | `example.com` | | `url_path` | URL path | `/stuff/index.html`, in the context of a URL | | `file` | File or path name | `/usr/local/foo.txt`, if not within a URL | | `sfloat` | Scientific notation | `-1.234e56` | | `float` | Decimal notation | `-1.234` | | `int` | Signed integer | `-1234` | | `uint` | Unsigned integer | `1234` | | `version` | Version number | `8.3.0` | | `tag` | XML tag | `<a href="dictionaries.html">` | | `entity` | XML entity | `&` | | `blank` | Space symbols | (any whitespace or punctuation not otherwise recognized) | > **Note:** 注意：一個"字母"的語法分析器的概念是由數據庫的區域設置決定的，特別是`lc_ctype`。只包含基本ASCII字母的詞作為一個單獨的標記類型被報告，因為區分他們有時候是有用的。大多數歐洲語言，標記類型`word`和`asciiword`應該一視同仁。 > > `email`不支持由RFC 5322定義的所有有效的電子郵件字符。具體來說，唯一的非字母數字字符支持電子郵件用戶名有句號，破折號和下劃線。對于分析器從文本的同一塊產生重疊的標記是可能的。作為一個例子，一個連字符的單詞將作為整個單詞和每個組件被報道： ``` SELECT alias, description, token FROM ts_debug('foo-bar-beta1'); alias | description | token -----------------+------------------------------------------+--------------- numhword | Hyphenated word, letters and digits | foo-bar-beta1 hword_asciipart | Hyphenated word part, all ASCII | foo blank | Space symbols | - hword_asciipart | Hyphenated word part, all ASCII | bar blank | Space symbols | - hword_numpart | Hyphenated word part, letters and digits | beta1 ``` 這種行為是可取的，因為它允許為整個復合詞和組件進行搜索。這里是另一個很好的例子: ``` SELECT alias, description, token FROM ts_debug('http://example.com/stuff/index.html'); alias | description | token ----------+---------------+------------------------------ protocol | Protocol head | http:// url | URL | example.com/stuff/index.html host | Host | example.com url_path | URL path | /stuff/index.html ```