On Wed, Apr 7, 2010 at 7:10 PM, Lance Norskog <goks...@gmail.com> wrote:
>> Since min(a,b) == -1*max(-1*a, -1*b), you could rewrite the previous
>> expression using this more complicated logic and it would work. But
>> that's ugly.
>>
>> Also, it would crash anyway. It looks like max currently requires one
>> of its arguments to be a float constant, and neither of our args would
>> be a float constant.
>
> Ouch. There should be a min() function. The identity function will be
> slower. But, the 'parse a float' code should take an integer format
> string and parse it.
I should have been more specific about why max (and thus why a
hypothetical min) is inadequate for expressing something like
min(ms(NOW),ms(NOW,mydatefield))
The problem is that while
max(popularity,4)
works, putting anything more complicated as a second argument to max
fails. For example, these all fail:
max(4,popularity)
max(price,popularity)
max(5,ms(NOW))
The stack trace in each case is along these lines:
java.lang.NumberFormatException: empty String
at
sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:994)
at java.lang.Float.parseFloat(Float.java:422)
at
org.apache.solr.search.QueryParsing$StrParser.getFloat(QueryParsing.java:553)
at
org.apache.solr.search.FunctionQParser.parseFloat(FunctionQParser.java:85)
at
org.apache.solr.search.ValueSourceParser$5.parse(ValueSourceParser.java:102)
at
org.apache.solr.search.FunctionQParser.parseValueSource(FunctionQParser.java:223)
at
org.apache.solr.search.FunctionQParser.parseValueSource(FunctionQParser.java:151)
at org.apache.solr.search.FunctionQParser.parse(FunctionQParser.java:40)
at
org.apache.solr.search.BoostQParserPlugin$1.parse(BoostQParserPlugin.java:58)
at org.apache.solr.search.QParser.getQuery(QParser.java:131)
at
org.apache.solr.handler.component.QueryComponent.prepare(QueryComponent.java:89)
This behavior is sort of documented at
http://wiki.apache.org/solr/FunctionQuery#max
which says that "max(x,c) returns the max of another function __and a
constant__".
I assume the decision to support only constants was made with
performance in mind.
>
> On Wed, Apr 7, 2010 at 3:41 PM, Chris Harris <rygu...@gmail.com> wrote:
>> I'm using function queries to boost more recent documents, using
>> something like the
>>
>> recip(ms(NOW,mydatefield),3.16e-11,1,1)
>>
>> approach described on the wiki:
>> http://wiki.apache.org/solr/FunctionQuery#Date_Boosting
>>
>> What I'd like to do is figure out the best way to tweak how documents
>> with missing date fields are handled.
>>
>> For reference, what the above expression does with docs with missing
>> mydatefield values is to treat those docs as if they were dated at the
>> epoch start. (This is because the default value for a missing field,
>> including a date field, is 0.)
>>
>> What I want to try, in contrast, is to treat docs with missing dates
>> as if they were dated NOW. Can anyone suggest a satisfying way to do
>> this? Here are some options that won't work:
>>
>> Option 1. Use map
>>
>> The most obvious way to do this would be to wrap the reference to
>> mydatefield inside a map, like this:
>>
>> recip(ms(NOW,map(mydatefield,0,0,ms(NOW)),3.16e-11,1,1))
>>
>> However, this throws an exception because map is hard-coded to take
>> float constants, rather than arbitrary subqueries.
>>
>> Option 2. Use min
>>
>> The second most obvious way is to replace ms(NOW,mydatefield) with
>> this expression:
>>
>> min(ms(NOW),ms(NOW,mydatefield)
>>
>> (Docs with mydatefield will have a very large ms(NOW,mydatefield) term.)
>>
>> However there is no min function, so that won't work.
>>
>> Option 2a. Fake min with max and multiplication
>>
>> Since min(a,b) == -1*max(-1*a, -1*b), you could rewrite the previous
>> expression using this more complicated logic and it would work. But
>> that's ugly.
>>
>> Also, it would crash anyway. It looks like max currently requires one
>> of its arguments to be a float constant, and neither of our args would
>> be a float constant.
>>
>
>
>
> --
> Lance Norskog
> goks...@gmail.com
>
