Indexing e-mails in Azure Search - azure

Question

I'm trying to best index contents of e-mail messages, subjects and email addresses. E-mails can contain both text and HTML representation. They can be in any language so I can't use language specific analysers unfortunately.
As I am new to this I have many questions:
First I used Standard Lucene analyser but after some testing and
checking what each analyser does I switched to using "simple"
analyser. Standard one didn't allow me to search by domain in
user#domain.com (It sees user and domain.com as tokens). Is "simple" the best I can use in my case?
How can I handle HTML contents of e-mail? I thought this should be
possible to do it in Azure Search but right now I think I would need
to strip HTML tags myself.
My users aren't tech savvy and I assumed "simple" query type will be
enough for them. I expect them to type word or two and find messages
containing this word/containing words starting with this word. From my tests it looks I need to append * to their queries to get "starting with" to work?

Answer 1

It would help if you included an example of your data and how you index and query. What happened, and what did you expect?
The standard Lucene analyzer will work with your user#domain.com example. It is correct that it produces the tokens user and domain.com. But the same happens when you query, and you will get records with the tokens user and domain.com.
CREATE INDEX
"fields": [
{"name": "Id", "type": "Edm.String", "searchable": false, "filterable": true, "retrievable": true, "sortable": true, "facetable": false, "key": true, "indexAnalyzer": null, "searchAnalyzer": null, "analyzer": null, "synonymMaps": [] },
{"name": "Email", "type": "Edm.String", "filterable": true, "sortable": true, "facetable": false, "searchable": true, "analyzer": "standard"}
]
UPLOAD
{
"value": [
{
"#search.action": "mergeOrUpload",
"Id": "1",
"Email": "user#domain.com"
},
{
"#search.action": "mergeOrUpload",
"Id": "2",
"Email": "some.user#some-domain.com"
},
{
"#search.action": "mergeOrUpload",
"Id": "3",
"Email": "another#another.com"
}
]
}
QUERY
Query, using full and all.
https://{{SEARCH_SVC}}.{{DNS_SUFFIX}}/indexes/{{INDEX_NAME}}/docs?search=user#domain.com&$count=true&$select=Id,Email&searchMode=all&queryType=full&api-version={{API-VERSION}}
Which produces results as expected (all records containing user and domain.com):
{
"#odata.context": "https://<your-search-env>.search.windows.net/indexes('dg-test-65392234')/$metadata#docs(*)",
"#odata.count": 2,
"value": [
{
"#search.score": 0.51623213,
"Id": "1",
"Email": "user#domain.com"
},
{
"#search.score": 0.25316024,
"Id": "2",
"Email": "some.user#some-domain.com"
}
]
}
If your expected result is to only get the record above where the email matches completely, you could instead use a phrase search. I.e. replace the search parameter above with search="user#domain.com" and you would get:
{
"#search.score": 0.51623213,
"Id": "1",
"Email": "user#domain.com"
}
Alternatively, you could use the keyword analyzer.
ANALYZE
You can compare the different analyzers directly via REST. Using the keyword analyzer on the Email property will produce a single token.
{
"text": "some-user#some-domain.com",
"analyzer": "keyword"
}
Results in the following tokens:
"tokens": [
{
"token": "some-user#some-domain.com",
"startOffset": 0,
"endOffset": 25,
"position": 0
}
]
Compared to the standard tokenizer, which does a decent job for most types of unstructured content.
{
"text": "some-user#some-domain.com",
"analyzer": "standard"
}
Which produces reasonable results for cases where the email address was part of some generic text.
"tokens": [
{
"token": "some",
"startOffset": 0,
"endOffset": 4,
"position": 0
},
{
"token": "user",
"startOffset": 5,
"endOffset": 9,
"position": 1
},
{
"token": "some",
"startOffset": 10,
"endOffset": 14,
"position": 2
},
{
"token": "domain.com",
"startOffset": 15,
"endOffset": 25,
"position": 3
}
]
SUMMARY
This is a long answer already, so I won't cover your other two questions in detail. I would suggest splitting them to separate questions so it can benefit others.
HTML content: You can use a built-in HTML analyzer that strips HTML tags. Or you can strip the HTML yourself using custom code. I typically use Beautiful Soup for cases like these or simple regular expressions for simpler cases.
Wildcard search: Usually, users don't expect automatic wildcards appended. The only application that does this is the Outlook client, which destroys precision. When I search for "Jan" (a common name), I annoyingly get all emails sent in January(!). And a search for Dan (again, a name), I also get all emails from Danmark (Denmark).
Everything in search is a trade-off between precision and recall. In your first example with the email address, your expectation was heavily geared toward precision. But, in your last wildcard question, you seem to prefer extreme recall with wildcards on everything. It all comes down to your expectations.