Hi All,
I'll explain what I'm working on, and then I'll ask my two questions.
I'm working on the issue
https://issues.apache.org/jira/browse/SOLR-380 which is a feature
request that allows one to index a "Structured Document" which is
anything that can be represented by XML in order to provide more context
to hits in the result set. This allows us to do things like query the
index for "Canada" and be able to not only say that that query matched a
document titled "Some Nonsense" but also that the query term appeared on
page 7 of chapter 1. We can then take this one step further and
markup/highlight the image of this page based on our OCR and position hit.
For example:
<book title='Some Nonsense'><chapter title='One'><page name='1'>Some
text from page one of a book.</page><page name='7'>Some more text from
page seven of a book. Oh and I'm from Canada.</page></chapter></book>
I accomplished this by creating a custom Tokenizer which strips the
xml elements and stores them as a Payload at each of the Tokens created
from the character data in the input. The payload is the string that
describes the XPath at that location. So for <Canada> the payload is
"/book[title='Some Nonsense']/chapter[title='One']/page[name='7']"
The other part of this work is the SolrHighlighter which is less
important to this list. I retrieve the TermPositions for the Query's
Terms and use the TermPosition functionality to get back the payload for
the hits and build output which shows hit positions categorized by the
payload they are associated with.
QUESTION 1: Applying TokenFilters to my Tokenizer creates some strange
(in my opinion) behavior. First of all the TermPositions change and
second the Payload is removed. Is this the expected behavior, or is
this a bug? With the Payload being an "experimental feature" I can
understand if this persistence just hasn't been implemented yet. But is
it, or will it be?
In the following example I will denote a token by {pos,<term
text>,<payload>}:
input: <class name='mammalia'>Dog, and Cat</class>
XmlPayloadTokenizer:
{1,<Dog,>,</class[name='mammalia'][startPos='0']>},{2,<and>,</class[name='mammalia'][startPos='0']>},{3,<Cat>,</class[name='mammalia'][startPos='0']>}
StopFilter:
{1,<Dog,>,</class[name='mammalia'][startPos='0']>},{2,<Cat>,</class[name='mammalia'][startPos='0']>}
WordDelimiterFilter:
{1,<Dog>,<>} {2,<Cat>,</class[name='mammalia'][startPos='0']>}
LowerCaseFilter:
{1,<dog>,<>} {2,<cat>,</class[name='mammalia'][startPos='0']>}
QUESTION 2: As I explained I'm storing the String representing the
XPath of the token as the Payload (well the ByteArray of the String) of
each token. Is there a more efficient way to do this? Is this
exploiting Payload functionality and will it turn around and bite me
when I get to indexing hundreds of thousands of documents? Perhaps I
shouldn't be relying on the Payload functionality before it is deemed
not experimental?
I feel these questions are both related to Lucene proper rather than
Solr, which is why I've posted here. If you think solr-user is a better
place to post my questions let me know.
Thanks for your input!
Tricia
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