I need do a filtering query with some query parameter. I need that if the query parameter is null, the condition of the query (= or LIKE, for example) is not evaluated and return me everything. I'm using R2DBC and I don't find a way to solve it.
If you are using Spring Data R2dbc, besides the above raw SQL query, you can use R2dbcOperations to compose Criteria by condition freely.
The following is an example.
template
.select(Post.class)
.matching(
Query
.query(where("title").like("%" + name + "%"))// extract where here you can assemble the query condition freely.
.limit(10)
.offset(0)
)
.all();
Additionally using R2dbcRepository and convention-based method, try to use a default value in the like(eg. set the null to empty string "" in like) to save work to determine if it is a null value in sql.
A general prepared statement which would work might be:
SELECT *
FROM yourTable
WHERE col = ? or ? IS NULL;
In the event that you bind a NULL value to the ? from your obfuscation layer, the WHERE clause would always be true, returning all records in the table.
If you prefer doing this with a "static SQL statement" (meaning you use a single SQL string for all possible bind values), then, in Oracle, it's probably optimal to use NVL() to profit from an Oracle optimiser feature, as explained in this article, irrespective of whether you're using R2DBC:
SELECT *
FROM t
WHERE col = nvl(:bind, col)
However, a query like yours is often best implemented using dynamic SQL, such as supported by a third party library like jOOQ:
Flux<TRecord> result =
Flux.from(ctx
.selectFrom(T)
.where(bind == null ? noCondition() : T.COL.eq(bind))
);
You can obviously also do this yourself, directly with R2DBC and your own dynamic SQL library, or any other such library.
Disclaimer: I work for the company behind jOOQ.
Related
I tried DapperExtensions, Dapper.Extensions.Linq and linq2dapper to no avail. I will try Dapper.SimpleCRUD-with-Oracle. I will probably settle with a Stored Procedure instead. I want to use TableDirect with no embedded SQL statement. How can I use Dapper and Linq with a TableDirect? Or, how can I use TableDirect without embedded SQL, and filter a table?
Following are my problems:
I could not create Predicate without run time error.
I need missing configuration
I got ORA error about table saying "column not correct, runtime error".
How to use Dapper LINQ with TableDirect (without embedded SQL) with ORACLE?
You can achieve this with simple Dapper. For example, look at the following code from Dapper:
public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = default(int?), CommandType? commandType = default(CommandType?));
Look at the last commandType parameter. It supports the TableDirect value that you are looking for.
As far as other extensions of Dapper you mentioned in question, I do not think they will support it. I know for sure Dapper Extensions do not support it; not sure about others.
This is because, those extensions are basic query generators written over Dapper. So, you are using them for generating the query and in that case, that parameter value will/should be Text. If you want to use other values, bypass the extension and use simple Dapper.
If you want to simply provide a table name or stored procedure name, why use query generator? Just use Dapper.
I used //https://github.com/jmo21/Dapper.SimpleCRUD-with-Oracle-/blob/master/Dapper.SimpleCRUD/SimpleCRUD.cs . No nuget package for this ORACLE dialect. It just obfuscates the WHERE clause, and it is an answer, when I the organization probably will not like SELECT.. FROM ... WHERE...
We don't have SQL injection possible in any case.
I have to implement a SQL statment with more than one subquery in Informatica PowerCenter.
In one of this I am stuck because I would use as suggested in another answer,2 Source Qualifier and then a Joiner Component, but I need to have the between condition as follow:
TableB.columnID BETWEEN TableA.columnID AND TableB.column_ID
Unfortunately I did not yet found a way to implement this condition that I so have in a where statement as you can see from the complete SQL.
More as far I know as far I know in PowerCenter the SQL transformation component cannot get imput from 2 Source Qualifiers.
The solution so far that I have found is to put the between condition in a SQL Override in Source Qualifier like in the image:
The all SQL statment and my solution so far as a SQL Override:
Match criteria in joiner Can only be '='
If the join is not a 'full outer' you can use a lookup transformation configured to return ALL rows on match (not any, first or last)
Match criteria in lookups can be '>=', '<=', '<>' as well as'='.
There is a guide available here: https://dwbi.org/etl/informatica/139-active-lookup-transformation
If you choose to use 2 source qualifiers and a joiner transformation, you can apply the between condition afterwards in a Filter transformation. You would have an expression like below in the filter transformation.
TableB_ID >= TableA_VON_ID AND TableB_ID <= TableB_BIS_ID
Is there a way to do
"UPDATE Item SET start_date = CURRENT_TIMESTAMP" ?
in Nhibernate without using hql/sql.
I am trying to avoid hql/sql because the rest of my code is in criteria. I want to do something like :
var item = session.get<Item>(id)
item.start_date = current_timestamp
There are two ways and sql is correct one.
Either you will
load all entities, change, update and commit, or
write sql query and let dbms handle most of the work
I am trying to avoid hql/sql because the rest of my code is in criteria
That is not a valid argument. Criteria is an API intended for relational search, and it does not support mass updates.
Different tasks, different APIs.
In this case, you can use either HQL or SQL, as the syntax is the same. I recommend the former, because you'll be using your entity/property names instead of table/column ones.
I'm tasked with adding an option to our search, which will return results where a given field doesn't begin with a letter of the alphabet. (The .StartsWith(letter) part wasn't so hard).
But I'm rather unsure about how to get the results that don't fall within the A-Z set, and equally hoping it generates some moderately efficient SQL underneath.
Any help appreciated - thanks.
In C# use the following construct, assuming db as a data context:
var query = from row in db.SomeTable
where !System.Data.Linq.SqlClient.SqlMethods.Like(row.SomeField, "[A-Z]%")
select row;
This is only supported in LINQ to SQL queries. All rules of the T-SQL LIKE operator apply.
You could also use less effective solution:
var query = from row in db.SomeTable
where row.SomeField[0] < 'A' || row.SomeField[0] > 'Z'
select row;
This gets translated into SUBSTRING, CAST, and UNICODE constructs.
Finally, you could use VB, where there appears to be a native support for the Like method.
Though SQL provides the ability to check a range of characters in a LIKE statement using bracket notation ([a-f]% for example), I haven't seen a linq to sql construct that supports this directly.
A couple thoughts:
First, if the result set is relatively small, you could do a .ToList() and filter in memory after the fact.
Alternatively, if you have the ability to change the data model, you could set up additional fields or tables to help index the data and improve the search.
--EDIT--
Made changes per Ruslan's comment below.
Well, I have no idea if this will work because I have never tried it and don't have a compiler nearby to try it, but the first thing I would try is
var query = from x in db.SomeTable
where x.SomeField != null &&
x.SomeField.Length >= 1 &&
x.SomeField.Substring(0, 1).All(c => !Char.IsLetter(c))
select x;
The possiblility exists that LINQ to SQL fails to convert this to SQL.
I have an Oracle database with all the "data", and a Solr index where all this data is indexed. Ideally, I want to be able to run queries like this:
select * from data_table where id in ([solr query results for 'search string']);
However, one key issue arises:
Oracle WILL NOT allow more than 1000 items in the array of items in the "in" clause (BIG DEAL, as the list of objects I find is very often > 1000 and will usually be around the 50-200k items)
I have tried to work around this using a "split" function that will take a string of comma-separated values, and break them down into array items, but then I hit the 4000 char limit on the function parameter using SQL (PL/SQL is 32k chars, but it's still WAY too limiting for 80,000+ results in some cases)
I am also hitting performance issues using a WHERE IN (....), I am told that this causes a very slow query, even when the field referenced is an indexed field?
I've tried making recursive "OR"s for the 1000-item limit (aka: id in (1...1000 or (id in (1001....2000) or id in (2001....3000))) - and this works, but is very slow.
I am thinking that I should load the Solr Client JARs into Oracle, and write an Oracle Function in Java that will call solr and pipeline back the results as a list, so that I can do something like:
select * from data_table where id in (select * from table(runSolrQuery('my query text')));
This is proving quite hard, and I am not sure it's even possible.
Things that I can't do:
Store full data in Solr (security +
storage limits)
User Solr as
controller of pagination and ordering
(this is why I am fetching data from
the DB)
So I have to cook up a hybrid approach where Solr really act like the full-text search provider for Oracle. Help! Has anyone faced this?
Check this out:
http://demo.scotas.com/search-sqlconsole.php
This product seems to do exactly what you need.
cheers
I'm not a Solr expert, but I assume that you can get the Solr query results into a Java collection. Once you have that, you should be able to use that collection with JDBC. That avoids the limit of 1000 literal items because your IN list would be the result of a query, not a list of literal values.
Dominic Brooks has an example of using object collections with JDBC. You would do something like
Create a couple of types in Oracle
CREATE TYPE data_table_id_typ AS OBJECT (
id NUMBER
);
CREATE TYPE data_table_id_arr AS TABLE OF data_table_id_typ;
In Java, you can then create an appropriate STRUCT array, populate this array from Solr, and then bind it to the SQL statement
SELECT *
FROM data_table
WHERE id IN (SELECT * FROM TABLE( CAST (? AS data_table_id_arr)))
Instead of using a long BooleanQuery, you can use TermsFilter (works like RangeFilter, but the items doesn't have to be in sequence).
Like this (first fill your TermsFilter with terms):
TermsFilter termsFilter = new TermsFilter();
// Loop through terms and add them to filter
Term term = new Term("<field-name>", "<query>");
termsFilter.addTerm(term);
then search the index like this:
DocList parentsList = null;
parentsList = searcher.getDocList(new MatchAllDocsQuery(), searcher.convertFilter(termsFilter), null, 0, 1000);
Where searcher is SolrIndexSearcher (see java doc for more info on getDocList method):
http://lucene.apache.org/solr/api/org/apache/solr/search/SolrIndexSearcher.html
Two solutions come to mind.
First, look into using Oracle specific Java extensions to JDBC. They allow you to pass in an actual array/list as an argument. You may need to create a stored proc (it has a been a while since I had to do this), but if this is a focused use case, it shouldn't be overly burdensome.
Second, if you are still running into a boundary like 1000 object limits, consider using the "rows" setting when querying Solr and leveraging it's inherent pagination feature.
I've used this bulk fetching method with stored procs to fetch large quantities of data which needed to be put into Solr. Involve your DBA. If you have a good one, and use the Oracle specific extensions, I think you should attain very reasonable performance.