Develop Reference

Couchbase query does not see documents add recently

I'm performing a test with CouchBase 4.0 and java sdk 2.2. I'm inserting 10 documents whose keys always start by "190".
After inserting these 10 documents I query them with:
cb.restore("190", cache);
Thread.sleep(100);
cb.restore("190", cache);
The query within the 'restore' method is:
Statement st = Select.select("meta(c).id, c.*").from(this.bucketName + " c").where(Expression.x("meta(c).id").like(Expression.s(callId + "_%")));
N1qlQueryResult result = bucket.query(st);
The first call to restore returns 0 documents:
Query 'SELECT meta(c).id, c.* FROM cache c WHERE meta(c).id LIKE "190_%"' --> Size = 0
The second call (100ms later) returns the 10 documents:
Query 'SELECT meta(c).id, c.* FROM cache c WHERE meta(c).id LIKE "190_%"' --> Size = 10
I tried adding PersistTo.MASTER in the 'insert' statement, but it neither works.
It seems that the 'insert' is not persisted immediately.
Any help would be really appreciated.
Joan.

You're using N1QL to query the data - and N1QL is only eventually consistent (by default), so it only shows up after the indices are recalculated. This isn't related to whether or not the data is persisted (meaning: written from RAM to disc).
You can try to change the scan_consitency level from its default - NOT_BOUNDED - to get consistent results, but that would take longer to return.
read more here
java scan_consitency options

ORMLite groupByRaw and groupBy issue on android SQLite db

I have a SQLite table content with following columns:
-----------------------------------------------
|id|book_name|chapter_nr|verse_nr|word_nr|word|
-----------------------------------------------
the sql query
select count(*) from content where book_name = 'John'
group by book_name, chapter_nr
in DB Browser returns 21 rows (which is the count of chapters)
the equivalent with ORMLite android:
long count = getHelper().getWordDao().queryBuilder()
.groupByRaw("book_name, chapter_nr")
.where()
.eq("book_name", book_name)
.countOf();
returns 828 rows (which is the count of verse numbers)
as far as I know the above code is translated to:
select count(*) from content
where book_name = 'John'
group by book_name, chapter_nr
result of this in DB Browser:
| count(*)
------------
1 | 828
2 | 430
3 | 653
...
21| 542
---------
21 Rows returned from: select count(*)...
so it seems to me that ORMLite returns the first row of the query as the result of countOf().
I've searched stackoverflow and google a lot. I found this question (and more interestingly the answer)
You can also count the number of rows in a custom query by calling the > countOf() method on the Where or QueryBuilder object.
// count the number of lines in this custom query
int numRows = dao.queryBuilder().where().eq("name", "Joe Smith").countOf();
this is (correct me if I'm wrong) exactly what I'm doing, but somehow I just get the wrong number of rows.
So... either I'm doing something wrong here or countOf() is not working the way it is supposed to.
Note: It's the same with groupBy instead of groupByRaw (according to ORMLite documentation joining groupBy's should work)
...
.groupBy("book_name")
.groupBy("chapter_nr")
.where(...)
.countOf()
EDIT: getWordDao returns from class Word:
#DatabaseTable(tableName = "content")
public class Word { ... }

returns 828 rows (which is the count of verse numbers)
This seems to be a limitation of the QueryBuilder.countOf() mechanism. It is expecting a single value and does not understand the addition of GROUP BY to the count query. You can tell that it doesn't because that method returns a single long.
If you want to extract the counts for each of the groups it looks like you will need to do a raw query check out the docs.

case statement in order by clause is not working in HQL

When i am using case statement in Hibernate Query with setMaxResults() and setFirstResult() it is showing wrong records. For example, my query is
select code, text
from dropDownTable
where (code like '%meter%' or text like '%meter%')
order by case
when text like 'meter%' or code like 'meter%' then 0
when text like '%meter' or code like '%meter' then 2 else 1
end
Now I am using setMaxResults(fetchSize) and setFirstResult(fetchSize*fetchCount) in Hibernate Query. It is showing same records when fetchCount is more than 1.
I am not getting point that when we are setting start index then why it is showing records which are before that index. Please help me out in this. Following is my java code:
Query managerQuery = session.createSQLQuery(dynamicQuery);
managerQuery.setMaxResults(fetchSize);
managerQuery.setFirstResult(fetchSize * fetchCount);
returnList = managerQuery.setResultTransformer(insensitiveAliasTransformer).list();

Automatically generated database requests

How do you implement automatically generated database (let it be SQL) requests?
Let us have offline shop with filters:
The database is standalone offline.
SO if I want to filter items by Price the request would be something like:
select Snowboard.Name
from Snowboard
where Snowboard.Price between 400 and 600;
And if I filter by two characteristics e.g. Price from and Camber. There would be:
select s.Name, s.Camber
from Snowboard s
where s.Price between 400 and 600
and s.Camber in ('Rocker', 'Hybrid');
The question is how could it be implemented in Java so that these requests are generated automatically from any combination of filters selected?

Quick and dirty solution #1
Generate a query at run time & make clever use of WHERE 1=1 condition as the number of where clause are unknown. (This sample is in C# but works more or less the same with JAVA as well)
string sql= #"select Snowboard.Name
from Snowboard
where 1=1";
Now you can build your query based on the UI element selections like
string whereClause="";
if(yourCheckBoxPrice.Checked)
{
whereClause+= " AND Price BETWEEN "+ txtPriceFrom.Text + " AND "+ txtPriceTo.Text;
}
if(yourCheckBoxCamber.Checked)
{
whereClause+= " AND Camber IN ("+ /* your list of values go here */ +")";
}
sql += whereClause;
2nd Solution (Use SQL CASE)
You can use SQL CASE inside your query for each where clause to check for nulls or specific values. But beware, dynamic SQL will make your code pretty messy & hard to read (Can be done via a stored procedure as well)
SQL- CASE Statement
I advise you to use a stored procedure with a mix of both options 1 and 2. Implementing Dynamic SQL Where Clause. Keep it simple and you are good to go.

AND OR search syntax in lucene

I am using Lucene. I have three columns which are
DocId - TermID - TermFrequency
1 - 004 - 667
2 - 005 - 558
If i use mysql then query for AND operation is
SELECT * FROM table_name WHERE DocId='1' AND TermId='004'
How can i write above query in Lucene using JAVA. For one column search code i am using is
Query query = new QueryParser(Version.LUCENE_35,"TermID", analyzer).parse("004");
How can i use AND operation in QueryParser ??

Terms can be grouped with the AND keyword like so:
Query query = new QueryParser(Version.LUCENE_35,"TermID", analyzer).parse("004 AND DocId:1");
Note that you don't need to qualify the field for your "004" term because you've set "TermId" as the default field.
You should read the manual on the query syntax...it's pretty expressive.