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I'm getting a weird behaviour using Oracle Text. I have created the following table:

CREATE TABLE TEST_OTEXT_TABLE (id NUMBER PRIMARY KEY, text VARCHAR2(200));

and populated the table with the following data:

1   California is a state in the US.
2   Paris is a city in France.
3   France is in Europe.
4   Italy is a city in Europe.

I've then created the index:

CREATE INDEX TEST_OTEXT_INDEX ON TEST_OTEXT_TABLE(text)
INDEXTYPE IS CTXSYS.CONTEXT 
parameters ('DATASTORE CTXSYS.DEFAULT_DATASTORE');

EXEC CTX_DDL.SYNC_INDEX('TEST_OTEXT_INDEX', '2M');

If I run 

select id, score(1) from TEST_OTEXT_TABLE WHERE CONTAINS (text, 'is a city', 1) > 0 ;

everything works fine as Oracle Text correctly returns

    ID   SCORE(1)
---------- ----------
     2          4
     4          4

However, if I run

select id, score(1) from TEST_OTEXT_TABLE WHERE CONTAINS (text, 'is a', 1) > 0 ;

it returns

no rows selected

instead of returning the very same result.

4

2 回答 2

1

is a are stopwords, that means they do not bear relevancy for a text they're likely not indexed at all you can edit the stopword list and remove words that you want to be indexed

于 2017-07-13T23:41:25.413 回答
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It is because score is too low:

select id, score(1) from TEST_OTEXT_TABLE WHERE CONTAINS (text, 'is a', 1) = 0 ;

Row   ID  SCORE
1     1   0
2     2   0
3     3   0
4     4   0

If you use city the score is 4 and results are shown:

select id, score(1) from TEST_OTEXT_TABLE WHERE CONTAINS (text, 'city', 1) > 0 ;

More info about score: https://docs.oracle.com/cd/A91202_01/901_doc/text.901/a90121/csql8.htm

Here you can read how score algoritm works: https://docs.oracle.com/cd/A91202_01/901_doc/text.901/a90121/ascore2.htm

于 2016-03-31T08:20:28.013 回答