There is a table from where I need to fetch paginated records by applying and condition in a list of paired values, Below is the explanation
Lets say I have a class Billoflading and there are various fields in it
The two important fields in the table are
tenant
billtype
I have a list of pairs which contain values as
[
{`tenant1`, `billtype1`},
{`tenant2`, `billtype2`},
{`tenant3`, `billtype3`},
....
]
I need a JPA query where the fetch will be like
findByTenantAndBilltypeOrTenantAndBillTypeOr.....
in simple sql query it will be like
Select * from `Billoflading` where
`tenant` = 'tenant1' and billtype = 'billtype1'
OR `tenant` = 'tenant2' and billtype = 'billtype2'
OR `tenant` = 'tenant3' and billtype = 'billtype3'
OR ......... so on..
I tried writing a JPA query as follows
Page<Billoflading> findByTenantInAndBillTypeIn(List<String> tenants, List<String> billTypes, Page page);
but this had crossover records as well
i.e it gave records for tenant1 and billtype2, benant2 and billtype 3 so on... which are not needed in the result set
can anyone please solve this and help me finding a simple solution like
Page<Billoflading> findByTenantAndBillTypeIn(Map<String, String> tenantsAndBilltyes, Page page);
I am also ready for the native queries in JPA all I need is there should be no crossovers as this is a very sensitive data
The other workaround I had was fetching the records and applying java 8 filters and that works but the no. of records in a page gets reduced
Section 4.6.9 of the JPA specification makes it clear that this is not supported by JPQL, at least not in the form of an in-clause:
4.6.9 In Expressions
The syntax for the use of the comparison operator [NOT] IN in a conditional expression is as follows:
in_expression ::=
{state_valued_path_expression | type_discriminator} [NOT] IN
{ ( in_item {, in_item}* ) | (subquery) | collection_valued_input_parameter }
in_item ::= literal | single_valued_input_parameter
The state_valued_path_expression must have a string, numeric, date, time, timestamp, or enum value.
The literal and/or input parameter values must be like the same abstract schema type of the state_valued_path_expression in type. (See Section 4.12).
The results of the subquery must be like the same abstract schema type of the state_valued_path_expression in type.
It just doesn't operate on tuples.
Your best bet is probably to create a Specification to construct the combination of AND and OR you require. See this blog article how to create Specifications
Related
I want to return arrays with data from the entire row (so all columns), not just a single column. I can do this with a raw sql statement in Postgresql,
SELECT
array_agg(users.*)
FROM users
WHERE
l_name LIKE 'Br%'
GROUP BY f_name;
but when I try to do it with SqlAlchemy, I'm getting
sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) can't adapt type 'InstrumentedAttribute'
For example, when I execute this query, it works fine
query: Query[User] = session.query(array_agg(self.user.f_name))
But with this I get arrays of rows with only one column value in them (in this example, the first name of a user) whereas I want the entire row (all columns for a user).
I've tried explicitly listing multiple columns, but to no avail. For example I've tried this:
query: Query[User] = session.query(array_agg((self.user.f_name, self.user.l_name))))
But it doesn't work. I get the above error message.
You could use Python feature unpack for create
example = [func.array_agg(column) for column in self.example.__table__.columns]
query = self.dbsession.query(*attach)
And after join results
I have an entity, let's call it Foo and a second one Bar
Foo can (but doesn't have to) have one or multiple Bar entries assigned. It looks something like this:
/**
* #ORM\OneToMany(targetEntity="Bar", mappedBy="foo")
* #ORM\OrderBy({"name" = "ASC"})
*/
private $bars;
I now would like to load in one case only Foo entities that have at least one Bar entity assigned. Previously, there was one foreach loop to traverse all Foo entries and if it had assigned entries, the Foo entry got assigned to an array.
My current implementation is in the FooRepository a function called findIfTheresBar which looks like this:
$qb = $this->_em->createQueryBuilder()
->select('e')
->from($this->_entityName, 'e')
/* some where stuff here */
->addOrderBy('e.name', 'ASC')
->join('e.bars', 'b')
->groupBy('e.id');
Is this the correct way to load such entries? Is there a better (faster) way? It kind of feels as if it should have a having(...) in the query.
EDIT:
I've investigated it a little further. The query should return 373 out of 437 entries.
Version 1: only using join(), this loaded 373 entries in 7.88ms
Version 2: using join() and having(), this loaded 373 entries in 8.91ms
Version 3: only using leftJoin(), this loaded all 437 entries (which isn't desired) in 8.05ms
Version 4: using leftJoin() and having(), this loaded 373 entries in 8.14ms
Since Version 1 which only uses an innerJoin as #Chausser pointed out, is the fastest, I will stick to that one.
Note: I'm not saying Version 1 will be the fastest in all scenarios and on every hardware, so kind of a follow up question, does anybody know about a performance comparison?
Please take a look at this answer for more information on how SQL JOINs work: https://stackoverflow.com/a/16598900/1307183
Using a join, which is an alias of innerJoin, is exactly what you want. This only returns records where entries exist in both Foo and Bar - aka where the association/attached entity exists. This calls INNER JOIN in SQL, which, if your database structure is defined correctly, is the absolute best and fastest way to get the data you want.
Using a leftJoin calls LEFT JOIN in SQL, which returns all records from Foo, even if there is no Bar associated with it (for example, where bar_id in your foo table would be null).
You have no reason to use having() in any of the above scenarios you described. If you want to filter further you would do that with a ->addWhere() function. Using the having() clause is something you would only want to do if you were selecting aggregate data in your original query (like SELECT SUM(field) AS sum_field).
I have a query which is written is using slick, it is not a plain slick query.
The query is a select query which fetches the records from a table called Employee. The results are of type Employee class.
Now there is a list of Strings
val nameFilter= List("Sachin","Naveen"")
and this "nameFilter" comes dynamically and it may have any number of names
var result= dbHandle.db.run((query.drop(10).take(10)).result
The variable query is just a select query for the Employee table which selects a range of records from 11 to 20.
Now I need to filter the records which have names mentioned in the 'nameFilter' and then select the records from 11 to 20. That means I need a query with 'IN' clause.
Please note that this is not a plain Slick SQL query, I have to frame a query in the above format.
You can do this with the method .inSet (see here):
Slick
Slick queries are composable. Subqueries can be simply composed, where the types work out, just like any other Scala code.
val address_ids = addresses.filter(_.city === "New York City").map(_.id)
people.filter(_.id in address_ids).result // <- run as one query
The method .in expects a sub query. For an in-memory Scala collection, the method .inSet can be used instead.
So that would mean for your code:
val nameFilter= List("Sachin","Naveen")
val filteredQuery = query.filter(_.name.inSet(nameFilter))
var result= dbHandle.db.run((filteredQuery.drop(10).take(10)).result
Depending on the source of that input you should consider using .inSetBind to escape the input (see this SO post).
I am using linq lambdas to query the MySql (Note MySql not Sql) with Entity Framwork in MVC. Now i have one table product one of column this table is price with datatype "VARCHAR" (Accept i can't change type to INT as it can hold values like "N/A",etc).
I want to sort price column numerically with linq Lambdas.I have tried bellow.I am using Model values to filter query.
var query = ent.Product.Where(b => b.cp == Model.CodePostal);
if (Model.order_by_flg == 2)
{
query = query.OrderByDescending(a => a.price.PadLeft(10, '0'));
}
But it will not work and give me bellow error.
LINQ to Entities does not recognize the method 'System.String
PadLeft(Int32, Char)' method, and this method cannot be translated
into a store expression.
As it cant convert to Sql statement by Entity Framwork.
I also tried bellow.
var query = ent.Product.Where(b => b.cp == Model.CodePostal);
if (Model.order_by_flg == 2)
{
query = query.OrderByDescending(a => a.price.Length).ThenBy(a => a.price);
}
But i can't do this because it works for List but i cant first make list and then do this as i am using linq Skip() and Take() so first i have to sort it.
So how can i sort price column of type "VARCHAR" in Linq lambda?
EDIT
In table it is :
59,59,400,185,34
Wnen i use OrderBy.ThenBy it gives
34,59,59,106,185,400
It looks right as sorting ascending But when i use OrderByDescending.ThenBy it gives
106,185,400,34,59,59
So i can't use this.
NOTE: Please give reasons before Downvote so i can improve my question...
You can simulate fixed PadLeft in LINQ to Entities with the canonical function DbFunctions.Right like this
instead of this
a.price.PadLeft(10, '0')
use this
DbFunctions.Right("000000000" + a.price, 10)
I haven't tested it with MySql provider, but canonical functions defined in the DbFunctions are supposed to be supported by any provider.
It looks right as sorting ascending But when i use OrderByDescending.ThenBy it gives
106,185,400,34,59,59
That's because you're ordering by length descending, then value ascending.
What you need is simply to sort both by descending;
query = query.OrderByDescending(a => a.price.Length)
.ThenByDescending(a => a.price);
This should be faster than prepending numbers to sort, since you don't need to do multiple calculations per row but can instead sort by existing data.
I have a few rows of data pulled into business objects via linq-to-sql from large tables.
Now I want to get a few rows that don't match to test my comparison functions.
Using what I thought would work I get a NotSupportedException:
Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
Here's the code:
//This table has a 2 field primary key, the other has a single
var AllNonMatches = from c in dc.Acaps
where !Matches.Rows.Any((row) => row.Key.Key == c.AppId & row.Key.Value == c.SeqNbr)
select c;
foreach (var item in AllNonMatches.Take(100)) //Exception here
{}
The table has a compound primary key: AppId and SeqNbr.
The Matches.Rows is defined as a dictionary of keyvaluepair(appid,seqnbr).
and the local sequence it is referring to appears to be the local dictionary.
Could you provide more information on the structure and the name(s) of the table(s) plz?
Not sure what you're trying to do...
edit:
Ok.. I think I get it now...
It appears you can't merge/join local tables (dictionary) with a SQL table.
If you can, I'm afraid I don't know how to do it.
The simplest solution I can think of is to put those results in a table ("Match" for instance) with foreign keys related to your table "Acaps" and then use linq-to-sql, like:
var AllNonMatches = dc.Acaps.Where(p=>p.Matchs==null).Take(100).ToList();
Sorry I couldn't come up with any better =(
What about this:
var AllNonMatches = from c in dc.Acaps
where !(Matches.Rows.ContainsKey(c.AppId) && Matches.Rows.ContainsValue(c.SeqNbr))
select c;
That will work fine. I have also used a bitwise AND operator (&&) - I think thats the right term to help improve performance over the standard AND operator.