Hibernate column order

Is it possible to use a JPA OrderColumn with Hibernate without making the order column nullable or giving it a default? I have an existing database with a sequence column mapped in a long-standing Hibernate 3, hibernate column order.

Off the top of my head, ' order by s. There are those who, when presented with a glass that is exactly half full, say: this glass is half full. And then there are those who say: this glass is half empty. The world belongs, however, to those who can look at the glass and say: 'What's up with this glass? Excuse me? This is my glass?

Hibernate column order

Developers often use the schemas as generated by Hibernate but currently we order columns in table DDL by name which can lead to inefficient physical layouts on a few DBs due to the need for padding. I propose we create a SPI for the ordering as well as a configuration parameter and by default order by coalesce staticOrder, Integer. I'd also like to add some kind of possibility to specify the order of columns through a static ordinal per column, if possible, but that would probably require a few changes to some annotations. Beta Was this translation helpful? Give feedback. I created the topic on discourse , I would love to participate, but I suspect this may be outside my skill level. My initial idea was a somewhat simple hack where you could set a property that toggles the following feature:. If possible would just retain the order in which the fields were defined in the java class. If this is not possible I suspect the JVM spec does not guarantee any ordering when traversing fields then add a simple ordering annotation that can be used with a comparator to sort the non-id columns prior to generation. I peeked around in the codebase and it looks doable without too much hassle, but I also understand that you need to keep the codebase clean without too many dirty hacks. The ColumnOrder annotation is actually an addition that allows fine grained control of the order. The main addition would be the SPI that allows automatic ordering based on some logic which a user configures just once. The default implementation would then order columns as outlined in the description above, which will make many users happy and can be used to solve the PK index selectivity issue Chris has in Envers due to the PK ordering. But it's terrible: I add a column to my table and in principle I might have to change an annotation on every other field. That's just awful.

But in big databases, this might be a noticeable difference.

Summary: Required Optional Detail: Element. The persistence provider is responsible for maintaining the order upon retrieval and in the database. The persistence provider is responsible for updating the ordering upon flushing to the database to reflect any insertion, deletion, or reordering affecting the list. The OrderColumn annotation is specified on the side of the relationship that references the collection that is to be ordered. The order column is not visible as part of the state of the entity or embeddable class. The OrderBy annotation should be used for ordering that is visible as persistent state and maintained by the application.

Most of the time it does not matter. However, the order of columns in a DB might impact the physical storage of the data. Columns are ordered in the way they were added to the table. The smallint column will be padded to the same size as the bigint column due to a mechanism called alignment padding. This wastes both storage and performance since the additional bytes need to be read and written. Of course, the impact on smaller databases will be negligible. But in big databases, this might be a noticeable difference. If you now put the bigint column first you save 6 bytes per row.

Hibernate column order

Summary: Required Optional Detail: Element. The persistence provider is responsible for maintaining the order upon retrieval and in the database. The persistence provider is responsible for updating the ordering upon flushing to the database to reflect any insertion, deletion, or reordering affecting the list. The OrderColumn annotation is specified on the side of the relationship that references the collection that is to be ordered.

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I agree, and that's one of the reasons why ColumnIndex seems like such a poor fit to the problem: it's not a natural way to define a partial order. If the auto-generated ecample uses the order column, you can debug that a d compare to your application to see where they differ. You signed in with another tab or window. I add a column to my table and in principle I might have to change an annotation on every other field. How would the matching to the PK work? Numbered list. Ordering columns by their physical size on the disk might improve the performance and disk space used in your database if you have lots of data. The OrderBy annotation is not used when OrderColumn is specified. Suggestions welcome. Just linking your GitHub fork is enough to share the replicating test case.

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So if we find an index that mentions all primary key columns and is unique, the we can treat that as definition for the primary key constraint. I actually think matching the column names is great as that would allow a user to provide a name for the PK constraint. Through a special name or by matching column names? That would be much more elegant than the ColumnOrder for the PK part of this issue in my opinion. I'm have no real knowledge of the hibernate internals, but I work on a project where we drive our data model through JPA combined with flyway. Reload to refresh your session. Let me rephrase my question: Is there a simple way to make sure that the order of a collection is the same as the order the elements where added? Report message. My initial idea was a somewhat simple hack where you could set a property that toggles the following feature: If possible would just retain the order in which the fields were defined in the java class. Map; import org. So the currently-proposed Instantiator annotation works like this:.