I am making a search tool to query against text fields.
If the user searches for:
6ES7-820
Than I would like to return all documents containing:
6ES7820
6-ES7820
6ES7-820
...
In other words I would like to ignore special characters. I could achieve this by removing the special characters in my search analyzer and my indexing analyzer.
But when the user would search for the same term using quotation marks (or something else):
"6ES7-820"
I want to only return the documents containing
6ES7-820
So then special characters should not be ignored. This means I can not remove these characters while indexing.
How could this search method be implemented in Elasticsearch, which analysers should I use?
Related
I have a custom analyzer that uses the "ngram" tokenizer and a pattern_replace character filter that removes all non-alphanumeric characters from the input.
so for example "+34 123 456 789"
turns into "34123456789"
and is then split up into 3grams.
The goal is to allow searching of phone numbers and other identifiers ignoring whitespace and special characters and allowing to search substrings as well.
Now, this works fine for searching, but highlighting is broken. As it says in the documentation of the pattern_replace character filter:
Using a replacement string that changes the length of the original text will work for search purposes, but will result in incorrect highlighting
So, I tried using the pattern_replace token filter instead, but that filter is applied to the 3gram tokens, which makes them unusable for searching.
Using the ngram filter instead of the ngram tokenizer doesn't help either, because the filter does not set the token positions correctly, resulting in the entire string being highlighted.
Is there a way to have the correct substring highlighted in this case?
Consider that I have a document which has a field with the following content: 5W30 QUARTZ INEO MC 3 5L
A user wants to be able to search for MC3 (no space) and get the document; however, search for MC 3 (with spaces) should also work. Moreover, there can be documents that have the content without spaces and that should be found when querying with a space.
I tried indexing without spaces (e.g. 5W30QUARTZINEOMC35L), but that does not really work as using a wildcard search I would match too much, e.g. MC35 would also match, and I only want to match two exact words concatenated together (as well as exact single word).
So far I'm thinking of additionally indexing all combinations of two words, e.g. 5W30QUARTZ, QUARTZINEO, INEOMC, MC3, 35L. However, does Elasticsearch have a native solution for this?
I'm pretty sure what you want can be done with the shingle token filter. Depending on your mapping, I would imagine you'd need to add a filter looking something like this to your content field to get your tokens indexed in pairs:
"filter_shingle":{
"type":"shingle",
"max_shingle_size":2,
"min_shingle_size":2,
"output_unigrams":"true"
}
Note that this is also already the default configuration, I just added it for clarity.
Hi I have a string field which has an nGram analyzer.
And our query goes like this.
$count=true&queryType=full&searchFields=name&searchMode=any&$skip=0&$top=50&search=/(.*)Site#12(.*)/
The test we are searching for has Site#123
The above query will work with all other alpha numeric charecters except #. Any idea how could I make this work.
If you are using the standard tokenizer, the ‘#’ character was removed from indexed documents as it’s considered a separator. For indexing, you can either use a different tokenizer, such as the whitespace tokenizer, or replace the ‘#’ character with another character such as ‘_’ with the mapping character filter (underscore ‘_’ is not considered a separator). You can test the analyzer behavior using the Analyze API : https://learn.microsoft.com/rest/api/searchservice/test-analyzer.
It’s important to know that the query terms of regex queries are not analyzed. This means that the ‘#’ character won’t be removed by the analyzer from the regex expression. You can learn more about query processing in Azure Search here: How full text search works in Azure Search
Your string is being tokenized by spaces and punctuation like #. If you want to search for # and other punctuation characters, you could consider tokenzing only by whitespace. Or perhaps do not apply any tokenization at all and treat a whole string as a single token.
I am indexing documents that may contain any special/reserved characters in their fulltext body. For example
"PDF/A is an ISO-standardized version of the Portable Document Format..."
I would like to be able to search for pdf/a without having to escape the forward slash.
How should i analyze my query-string and what type of query should i use?
The default standard analyzer will tokenize a string like that so that "PDF" and "A" are separate tokens. The "A" token might get cut out by the stop token filter (See Standard Analyzer). So without any custom analyzers, you will typically get any documents with just "PDF".
You can try creating your own analyzer modeled off the standard analyzer that includes a Mapping Char Filter. The idea would that "PDF/A" might get transformed into something like "pdf_a" at index and query time. A simple match query will work just fine. But this is a very simplistic approach and you might want to consider how '/' characters are used in your content and use slightly more complex regex filters which are also not perfect solutions.
Sorry, I completely missed your point about having to escape the character. Can you elaborate on your use case if this turns out to not be helpful at all?
To support queries containing reserved characters i now use the Simple Query String Query (https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-simple-query-string-query.html)
As of not using a query parser it is a bit limited (e.g. no field-queries like id:5), but it solves the purpose.
In the docs for query string query, auto_generate_phrase_queries is listed as a parameter but the only description is "defaults to false." So what does this parameter do exactly?
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-query-string-query.html
This will directly match to the lucene's org.apache.lucene.queryparser.classic.QueryParserSettings#autoGeneratePhraseQueries. When the analyzer applied on the query string, this setting allows lucene to generate quoted phrases no keywords.
Quoting:
SOLR-2015: Add a boolean attribute autoGeneratePhraseQueries to TextField.
autoGeneratePhraseQueries="true" (the default) causes the query parser to
generate phrase queries if multiple tokens are generated from a single
non-quoted analysis string. For example WordDelimiterFilter splitting text:pdp-11
will cause the parser to generate text:"pdp 11" rather than (text:PDP OR text:11).
Note that autoGeneratePhraseQueries="true" tends to not work well for non whitespace
delimited languages.
where word delimiter works as WordDelimiterFilter.html
Important thing to note is single non-quoted analysis string, i.e. if your query string is non-quoted. If you are already searching for a quoted phrase then it won't make any sense.