There is a performance benefit as JDXA can efficiently dispense many unique sequence ids before making a database trip for the next set of unique sequence ids. Using a JDXA provided named sequence generator: programmatically generating and assigning the unique ids to the primary key attributes. Moreover, if the object is subsequently fetched from the database using a query, it would come with its primary key attribute value properly initialized. This may not matter if the app does not need the primary key value right away. The database-generated primary key attribute value is not immediately available for use in the app after the object is inserted (saved). There is a performance benefit as JDXA does not have to perform an additional database call to obtain the value of the AUTOINCREMENT column after inserting other column values of the object. Using AUTOINCREMENT database column: JDXA does not initialize the primary key attribute with the database-generated column value. There is a performance penalty as JDXA has to perform an additional database call to obtain the value of the AUTOINCREMENT column after inserting other column values of the object. The database-generated primary key attribute value is immediately available for use in the app after the object is inserted (saved). Using AUTOINCREMENT database column: JDXA initializes the primary key attribute with the database-generated column value. Pros and Cons of different techniques for primary key generation: Those who suffer from VSD will understand me perfectly. After a while the anxiety recedes, the sweating of the palms disappears, at the same time the tremor goes away. The drug is beginning to act somewhere with an hour and a half. I started drinking and the drug suited me perfectly. She prescribed me a quarter of a pill Klonopin by at bedtime. You may pass the empSeqUtil.getNextSeq()value directly to a constructor of the Employee class instead of using the setId() method. However, since any unused sequence values in this session will be unavailable (lost) for the next session, you may not want to use a very high increment value. The higher the value, the more efficient the sequence generation operation would be because it would require fewer database trips to fetch (reserve) the next set of unique sequences. The sequence increment value of 5 may be changed depending on the needs of your app per session. JdxHandle.insert(emp, 0, null) emp = new Employee("Bob", …) Create and save a few Employee objects JDXSeqUtil empSeqUtil = new JDXSeqUtil("EmpIdSequence", jdxSetup, 5) this case per the mapping definition of EmpIdSequence By the way, the maximum increment value can be 10 in database for the next set of 5 unique id values.
can provide 5 unique sequence id values before going to the
#Android studio sqlite autoincrement integer non primary key generator#
Initialize a sequence generator for EmpIdSequence such that it Let’s assume the following definition of a persistent class Employee, where the id attribute serves as the primary key: However, these techniques may also work with other databases if the databases provide a similar functionality (e.g., an AUTOINCREMENT column). With regard to generating unique primary key values of persistent objects, some parts of the following discussion assume that JDXA ORM is used with a SQLite database. The article ends with pros and cons of using these different techniques. Incidentally, with the unique sequence generator feature of JDXA (described below), one may also create a “ String” value for a primary key attribute by concatenating the “ long” value returned by a sequence generator with some other text.
In this article, we will primarily discuss a few techniques for generating primary key attribute values in which the primary key consists of only one attribute whose data type is “ int” or “ long”. If the primary key value for a new object is not available from the data source, it needs to be somehow generated as part of the persistence mechanism. For example, data for an object may be retrieved from a server and that data may also contain the primary key value. JDXA, an innovative Object Relational Mapping (ORM) product, can handle both single attribute and composite primary keys.Ī primary key value may be readily available from the data source from which a persistent object is created in an app. For example, a UUID string may serve as a primary key attribute value. The data type of a primary key attribute is typically “ int” or “ long” but it could also be “ String”. A primary key may consist of only one attribute, or it may consist of multiple attributes (composite primary key). Using primary keys to uniquely identify persistent objects is a fundamental requirement for all apps.
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