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update the migration guide

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Steve Ebersole 2023-03-30 23:13:19 -05:00
parent 82714e5ae9
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migration-guide.adoc
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@ -132,16 +132,22 @@ LEGACY:: Allows the use of the wrapper arrays stored as `VARBINARY` and `VARCHAR
See link:{javadocsBase}/org/hibernate/cfg/AvailableSettings.html#WRAPPER_ARRAY_HANDLING[AvailableSettings#WRAPPER_ARRAY_HANDLING]
A possible migration could involve the following steps in a migration script:
The main idea here is for applications using these types in the domain model to make a conscious decision about how these
values are stored.
* Execute `alter table tbl rename column array_col to array_col_old` to have the old format available
* Execute `alter table tbl add column array_col DATATYPE array` to add the column like the new mapping expects it to be
* Run the query `select t.primary_key, t.array_col_old from table t` to extract `byte[]` or `String`
* For every result, load the Hibernate entity by primary key and set the field value to transformed result `Byte[]` or `Character[]`
* Finally, drop the old column `alter table tbl drop column array_col_old`
For those using such mappings, there are a few options -
Alternatively, to revert to pre-6.2 behavior for specific properties, annotate your array property with `@JavaType(ByteArrayJavaType.class)`
or `@JavaType(CharacterArrayJavaType.class)` or simply change the domain model type to `byte[]` and `char[]` respectively.
1. Migrate the domain model to use `byte[]` and `char[]` instead.
2. Specify `hibernate.type.wrapper_array_handling=legacy` to enable the legacy behavior.
3. Specify `@JavaType(ByteArrayJavaType.class)` or `@JavaType(CharacterArrayJavaType.class)` attribute-by-attribute
4. Specify `hibernate.type.wrapper_array_handling=allow`. If the schema is legacy, migrate the database schema to use a structured SQL type. E.g.
a. Execute `alter table tbl rename column array_col to array_col_old` to have the old format available
b. Execute `alter table tbl add column array_col DATATYPE array` to add the column like the new mapping expects it to be
c. Run the query `select t.primary_key, t.array_col_old from table t` to extract `byte[]` or `String`
d. For every result, load the Hibernate entity by primary key and set the field value to transformed result `Byte[]` or `Character[]`
e. Finally, drop the old column `alter table tbl drop column array_col_old`
NOTE: Some mappings are considered implicit opt-in to the legacy behavior; e.g. using `@Lob` or `@Nationalized`
[[ddl-check]]
=== Check constraints for boolean and enum mappings