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From Arturas Mazeika <maze...@gmail.com>
Subject some parent documents
Date Tue, 03 Apr 2018 14:14:00 GMT
Hi Solr Fans,

I am trying to make sense of information retrieval using expressions like
"some parent", "*only parent*", " *all parent*". I am also trying to
understand the syntax "!parent which" and "!child of". On the technical
level, I am reading the following documents:

[1]
https://lucene.apache.org/solr/guide/7_2/other-parsers.html#block-join-query-parsers
[2]
https://lucene.apache.org/solr/guide/7_2/uploading-data-with-index-handlers.html#nested-child-documents
[3] http://yonik.com/solr-nested-objects/

and I am confused to read:

This parser takes a query that matches some parent documents and returns
their children. The syntax for this parser is: q={!child
of=<allParents>}<someParents>. The parameter allParents is a filter that
matches *only parent documents*; here you would define the field and value
that you used to identify *all parent documents*. The parameter someParents
identifies a query that will match some of the parent documents. The output
is the children.

The first sentence talks about "matching" but does not define what that
means (and why it is only some parents matching?). The second sentence
introduces a syntax of the parser, but blurs the understanding as "some"
and "all" of parents are combined into one sentence. My understanding is
that all documents are retrieve that satisfy a query. The query must
express some constraints on the parent node and some on the child node. I
have a feeling that "only parent documents" reads "criteria is formulated
over the parent part of {parent document}->{child document} of entity.
My simplified conceptual world of solr looks in the following way:

1. Every document has an ID.
2. Every document may have additional attributes
3. Text attributes is what's at stake in solr. Sure we can search for
products that costs at most X, but this is the added functionality. For
simplicity I am neglecting those here.
4. The user has an information need. She expresses it with (key)words and
hopes to find matching documents. For simplicity, I am skipping all issues
related to the information presentation of the documents
5. Analysis chain (and inverse index) are the key technologies solr is
based upon. Once the chain-processing is applied, mathematical logic kicks
in, retrieving the documents (that are a set of processed, normalized,
enriched tokens) matching the query (processed, normalized and enriched
tokens). Clearly, the logic function can be a fancy one (at least one of
query token is in the document set of tokens, etc.), ranking is used to
sort the results.
6. A nested document concept is introduced in solr. It needs to be uploaded
into the index structure using a specific handlers [2]. A nested documents
is a tree. A root may contain children documents, which may be parents of
grandchildren documents.
7. Querying nested documents is supported in the following manner:
    7.1 Child documents are return that satisfies {parent
document}->{document}
    7.2 Parent documents are return that satisfy {document}->{child
document}

Would I be very wrong to have this conceptual picture?

>From this point, the situation is a bit bury in my head. At the core, I do
not really understand what "a document" is anymore (since the complete json
or xml, so is a sub-json and sub-xml are documents, every document must
have an ID, does that meant the the subdocuments must have and ID too, or
sub-ids are also fine?), how to formulate mathematical expressions over
documents and what it means that the document satisfies my (key)word query?
Can we define a document to be the largest entity of information that does
not contain any other nested documents [4]? If this is defined and
communicated like this already where can I find it? There is a use of the
clarification, as the concept of the document means different things in
different contexts (e.g., you can update only the "complete document" in
the index vs. parent document, etc.).

Is it possible to formulate what's going on using mathematical logic? Can
one express something like

{ give documents d : d is a document, d is parent of document c, d
satisfies logical criteria C1,....,CN, c satisfies logical criteria
C1',...,CM'}
{ give documents c : c is a document, d is parent of document c, d
satisfies logical criteria C1,....,CN, c satisfies logical criteria
C1',...,CM'}

here the meaning of document is as in definition [4] above.

1. Is it possible to retrieve all parent documents that have two children
c1 and c2? Consider a document that is a skype chat, and children are
individual lines of communication in the chat. I would be looking for the
(parent) documents that have "hello" said by person A and "ciao" said by
person B (as two different sub-documents).

2. Is it possible to search for documents such that they have a grandchild
and the grandchild has the word "hello"?

3. Is it possible to search for documents that do not have children?

Is this the right venue to discuss documentation of solr?

Thanks!
Arturas

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