About COUNT

GROUP BY and HAVING clauses

Explains how to use the GROUP BY and HAVING clauses in a JPA/JPQL query.... value combination). Aggregate calculations (count, sum, avg, max, min) that are carried out on all the objects (or the ... the five aggregate functions of SQL: COUNT - returns a long value representing the number of elements. ...

count(x)

Create an aggregate expression applying the count operation.(Method of javax.persistence.criteria.CriteriaBuilder)

Negative snapshot user count

I finally hit an instance of the "Negative snapshot user count" exception 1) ... I finally hit an instance of the "Negative snapshot user count" exception 1) [ObjectDB 2.3.2_01] Unexpected exception ... Negative snapshot user count com.objectdb.o.InternalException: Negative snapshot user count at com.objectdb.o.SNP.z(SNP.java:292) at ...

Strings in JPQL and Criteria Queries

Explains string expressions in JPQL queries, including LIKE, LOCATE, LOWER, UPPER, TRIM, CONCAT and SUBSTRING. String values may appear in JPQL queries in various forms: as string literals - e.g. 'abc' , ''. as parameters - when string values are assigned as arguments. as path e ...

ClassCastException thrown when running count query

Hello! Attached you find a full stacktrace. The query was: ... a full stacktrace. The query was: SELECT COUNT ( t ) FROM Position t WHERE ( ( t. unit = ... produces a null pointer exception. Now back to the count query: SELECT COUNT ( t ) FROM Position t ...

Processing thread count for 8-core server

In reference to the information here: http://www.objectdb.com/java/jpa/setting/database#The_processing_element_ We are working with an 8-core processor. The recommended thread count is "more than the number of cores but not too many." What would be an appropriate number of threads for the processing thread pool in order to get good performance for our 8-core server? ... with an 8-core processor. The recommended thread count is "more than the number of cores but not too many." What would be ...

countDistinct(x)

Create an aggregate expression applying the count distinct operation.(Method of javax.persistence.criteria.CriteriaBuilder)

Suspected memleak caused by bad state of EntityManager

Our application manages the Entities itself, so we close the EntityManager after every creating and using. We find a slow memleak in our application recently, and by trace of Entity construct and finalize, we found the problem is caused by bad state of EntityManager. After first throwing the InternalException, the EntityManager throws every time when doing merge operation, but it can be closed and retrieved by EntityManagerFactory, and the instances of Entity constructed by ObjectDB can never be released by JVM.There is a chart describes the instances exists in memory.... null chart1.jpg (Entity count in memory, our application only references about 2000 instances) ...

javax.persistence.criteria.CriteriaBuilder

Used to construct criteria queries, compound selections, expressions, predicates, orderings.(Interface of JPA)

Issue with UPPER ?

Hi, Assuming those queries which are all the same except the UPPER calls: ... ( 1 ) </ strong > SELECT COUNT ( $1 ) FROM com . lexware . vereinsverwaltung . ... ( 2 ) </ strong > SELECT COUNT ( $1 ) FROM com . lexware . vereinsverwaltung . ...