On Tue, Aug 17, 2010 at 4:10 PM, Brad Dewar <bde...@stfx.ca> wrote:
> When items are sorted, are all the docs with the sort field missing
> considered "tied" in terms of their sort order, or are they "indeterminate",
> or do they have some arbitrary order imposed on them (e.g. _docid_)?
If it's a numeric field, it sorts as if the value was 0.
If it's a string field, a missing value is less than other values.
All ties (regardless of missing or not) are broken by docid, and all
docs with a missing value are tied.
The "string" field from the solr example schema has
sortMissingLast="true" set, and so missing will sort after documents
with the value, regardless of sort order. Here's the blurb from the
example schema:
<!-- The optional sortMissingLast and sortMissingFirst attributes are
currently supported on types that are sorted internally as strings.
This includes
"string","boolean","sint","slong","sfloat","sdouble","pdate"
- If sortMissingLast="true", then a sort on this field will
cause documents
without the field to come after documents with the field,
regardless of the requested sort order (asc or desc).
- If sortMissingFirst="true", then a sort on this field will
cause documents
without the field to come before documents with the field,
regardless of the requested sort order.
- If sortMissingLast="false" and sortMissingFirst="false" (the default),
then default lucene sorting will be used which places docs without the
field first in an ascending sort and last in a descending sort.
-->
> For example, would "b" be considered as part of the sort in the following
> query, or would all the missing 'a' fields be in some kind of order already,
> thus making the sort algorithm never check the 'b' field?
>
> /select/?q=-a:[* TO *]&sort=a asc,b asc
>
> And would sortMissingLast / sortMissingFirst affect the answer to that
> question?
>
> I've been seeing weird behaviour in my index with queries (a little) like
> this one, but I haven't pinpointed the problem yet.
Are you using Solr 1.4? There was a bug with sortMissingLast/sortMissingFirst.
https://issues.apache.org/jira/browse/SOLR-1777
-Yonik
http://www.lucidimagination.com
