python - Whoosh 返回空值

Question

我正在使用 Whoosh 索引和搜索各种编码的各种文本。但是，在对我的索引文件执行搜索时，一些匹配结果没有出现在使用“突出显示”功能的输出中。我觉得这与编码错误有关，但我无法弄清楚是什么阻止了所有结果的显示。如果其他人可以阐明这个谜团，我将不胜感激。

这是我用来创建索引的脚本，here是我正在编制索引的文件:

from whoosh.index import create_in
from whoosh.fields import *
import glob, os, chardet

encodings = ['utf-8', 'ISO-8859-2', 'windows-1250', 'windows-1252', 'latin1', 'ascii']

def determine_string_encoding(string):
    result = chardet.detect(string)
    string_encoding = result['encoding']
    return string_encoding

#specify a list of paths that contain all of the texts we wish to index
text_dirs = [

"C:\Users\Douglas\Desktop\intertextuality\sample_datasets\hume",
"C:\Users\Douglas\Desktop\intertextuality\sample_datasets\complete_pope\clean"

]

#establish the schema to be used when storing texts; storing content allows us to retrieve hightlighted extracts from texts in which matches occur
schema = Schema(title=TEXT(stored=True), path=ID(stored=True), content=TEXT(stored=True))

#check to see if we already have an index directory. If we don't, make it
if not os.path.exists("index"):
    os.mkdir("index")
ix = create_in("index", schema)

#create writer object we'll use to write each of the documents in text_dir to the index
writer = ix.writer()

#create file in which we can write the encoding of each file to disk for review
with open("encodings_log.txt","w") as encodings_out:

    #for each directory in our list
    for i in text_dirs:

        #for each text file in that directory (j is now the path to the current file within the current directory)
        for j in glob.glob( i + "\\*.txt" ):

            #first, let's grab j title. If the title is stored in the text file name, we can use this method:
            text_title = j.split("\\")[-1]

            #now let's read the file
            with open( j, "r" ) as text_content:
                text_content = text_content.read()

                #use method defined above to determine encoding of path and text_content
                path_encoding = determine_string_encoding(j)
                text_content_encoding = determine_string_encoding(text_content)

                #because we know the encoding of the files in this directory, let's override the previous text_content_encoding value and specify that encoding explicitly
                if "clean" in j:
                    text_content_encoding = "iso-8859-1"

                #decode text_title, path, and text_content to unicode using the encodings we determined for each above
                unicode_text_title = unicode(text_title, path_encoding)
                unicode_text_path = unicode(j, path_encoding)
                unicode_text_content = unicode(text_content, text_content_encoding)

                #use writer method to add document to index
                writer.add_document( title = unicode_text_title, path = unicode_text_path, content = unicode_text_content )

#after you've added all of your documents, commit changes to the index
writer.commit()

该代码似乎可以毫无问题地对文本进行索引，但是当我使用以下脚本解析索引时，我在 out.txt 输出文件中得到了三个空白值——前两行为空，第六行是空的，但我希望这三行是非空的。这是我用来解析索引的脚本:

from whoosh.qparser import QueryParser
from whoosh.qparser import FuzzyTermPlugin
from whoosh.index import open_dir
import codecs

#now that we have an index, we can open it with open_dir
ix = open_dir("index")

with ix.searcher() as searcher: 
    parser = QueryParser("content", schema=ix.schema)

    #to enable Levenshtein-based parse, use plugin
    parser.add_plugin(FuzzyTermPlugin())

    #using ~2/3 means: allow for edit distance of two (where additions, subtractions, and insertions each cost one), but only count matches for which first three letters match. Increasing this denominator greatly increases speed
    query = parser.parse(u"swallow~2/3")
    results = searcher.search(query)

    #see see whoosh.query.phrase, which describes "slop" parameter (ie: number of words we can insert between any two words in our search query)

    #write query results to disk or html
    with codecs.open("out.txt","w") as out:

        for i in results[0:]:    

            title = i["title"]
            highlight = i.highlights("content")
            clean_highlight = " ".join(highlight.split())

            out.write(clean_highlight.encode("utf-8") + "\n")

如果有人能提出这三行是空的原因，我将永远感激不已。

Answer 1

天啊，我可能已经想通了!似乎我的一些文本文件(包括路径中带有“hume”的两个文件)超过了控制 Whoosh 索引创建行为的阈值。如果试图索引一个太大的文件，Whoosh 似乎将该文本存储为字符串值，而不是 unicode 值。因此，假设有一个包含字段“path”(文件路径)、“title”(文件标题)、“content”(文件内容)和“encoding”(当前文件的编码)的索引，可以测试是否通过运行如下脚本正确索引了该索引中的文件:

from whoosh.qparser import QueryParser
from whoosh.qparser import FuzzyTermPlugin
from whoosh.index import open_dir
import codecs

#now that we have an index, we can open it with open_dir
ix = open_dir("index")

phrase_to_search = unicode("swallow")

with ix.searcher() as searcher: 
    parser = QueryParser("content", schema=ix.schema)

    query = parser.parse( phrase_to_search )
    results = searcher.search(query)

    for hit in results:    
        hit_encoding = (hit["encoding"])

        with codecs.open(hit["path"], "r", hit_encoding) as fileobj:
            filecontents  = fileobj.read()
            hit_highlight = hit.highlights("content", text=filecontents)
            hit_title     = (hit["title"])

            print type(hit_highlight), hit["title"]

如果任何打印值的类型为“str”，那么荧光笔似乎将指定文件的一部分视为字符串类型而不是 unicode。

这里有两种方法可以纠正这个问题:1) 将大文件 ( anything over 32K characters ) 拆分成较小的文件——所有文件应包含 < 32K 个字符——并对这些较小的文件进行索引。这种方法需要更多的管理，但可以确保合理的处理速度。 2) 将参数传递给结果变量以增加可以存储为 unicode 的最大字符数，从而在上面的示例中正确打印到终端。要在上面的代码中实现此解决方案，可以在定义 results 的行之后添加以下行:

results.fragmenter.charlimit = 100000

添加此行允许将指定文件的前 100000 个字符的任何结果打印到终端，但它会显着增加处理时间。或者，可以使用 results.fragmenter.charlimit = None 完全删除字符限制，但这确实会增加处理大文件时的处理时间...