#6 tologx/query-engine - probs with value-like

[Maximilian Schwinger]

I try to perform a value-like - query. Therefore I wanted to
register a FullTextIndex. My Problem: How can I do this:

At first I need an IndexProvider, which I can initialise
with my topicMap. After that I have to register the
IndexProvider in the TopicMap's IndexManager.

How can I get an IndexProvider?

[Kal Ahmed]

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user_id=176992

You need to instantiate the class
org.tm4j.topicmap.memory.index.LuceneFullTextIndexProvider,
and then pass that instance into the registerIndexProvider
method on the IndexManager.

Note that you need to pass a Properties instance in to the
constructor of the LuceneFullTextIndexProvider. The
properties that are recognised are documented in the class
org.tm4j.topicmap.index.text.LuceneIndexBase

[Maximilian Schwinger]

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user_id=1055019

Thank you!!
So far it's working now. My next problem is to perform a
query. I tried to perform this one (from
accountingontology.com):

select $TOPIC from topic-name($TOPIC, $NAME), value-like
($NAME, "test") ?

and get the following stack-trace:

org.tm4j.tologx.TologParserException: Error parsing query
string.
at
org.tm4j.tologx.memory.QueryEvaluatorImpl.prepareQuery
(QueryEvaluator
Impl.java:156)
at CommandReceiver.performQuery
(CommandReceiver.java:36)
at test.main(test.java:41)
Caused by: line 1:65: unexpected token: "test"
at org.tm4j.tologx.parser.TologParser.expr
(TologParser.java:1258)
at org.tm4j.tologx.parser.TologParser.pair
(TologParser.java:1165)
at org.tm4j.tologx.parser.TologParser.predclause
(TologParser.java:1099)
at org.tm4j.tologx.parser.TologParser.clause
(TologParser.java:800)
at org.tm4j.tologx.parser.TologParser.clauselist
(TologParser.java:457)
at org.tm4j.tologx.parser.TologParser.query
(TologParser.java:512)
at
org.tm4j.tologx.memory.QueryEvaluatorImpl.prepareQuery
(QueryEvaluator
Impl.java:152)

[Kal Ahmed]

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user_id=176992

Actually, it looks like this is a bug with the parser that
has gone undetected. From inspection of the tolog.g grammar,
it looks like the parser only allows a variable or a direct
topic reference to go where you have the string value.
Unfortunately it also looks like the rest of the supporting
infrastructure of the parser doesn't really handle the
string either.

However, I think that there is a work-around. If you use a
placeholder in the query string and then evaluate with the
string as a value:

So write your query as:

select $TOPIC from value-like($NAME, "test"),
topic-name($TOPIC, %1) ?

Then evaluate with something like:

String queryString="select $TOPIC from value-like($NAME,
"test"), topic-name($TOPIC, %1) ?"
Object[] myParams = {"Test"};
myEvaluator.execute(queryString, myParams);

I think that should work, but haven't had chance to check it
out.

BTW: You should write your queries so that the most specific
clause comes first (as I have done above). I am assuming
that the value-like clause should match fewer
names/occurrences than the topic-name clause (i.e. all
names/occs containing the value "test" vs. all names of all
topics!) . You should always consider that the evaluator
always works from left-to-right using each clause to filter
the results from the last one, so if you make your first
clause return a smaller result set, the evaluation will be
faster.

[Maximilian Schwinger]

Logged In: YES
user_id=1055019

Thanks. I modified your query and this one works fine:

String queryString="select $TOPIC from value-like($NAME,
%1), topic-name($TOPIC, $TOPIC ) ?"
Object[] myParams = {"Test"};
myEvaluator.execute(queryString, myParams);

Thanks fr the performance-tips, too.