AI-generated Key Takeaways
-
Migrator is an abstract class used to translate GenericDocument objects between different versions of AppSearchSchema.
-
Non-backwards-compatible schema changes without a migrator will delete all old documents.
-
Migration methods
onDowngradeoronUpgradeare triggered when the schema version in AppSearch differs from the requested version. -
Any error in
onDowngradeoronUpgradewill reject thesetSchemarequest for non-backwards-compatible changes. -
The
shouldMigratemethod determines if a specific schema version update requires migration.
A migrator class to translate GenericDocument
from different version of AppSearchSchema
Make non-backwards-compatible changes will delete all stored documents in old schema. You
can save your documents by setting Migrator
via
the SetSchemaRequest.Builder.setMigrator(String, Migrator)
for each type and target
version you want to save.
onDowngrade(int, int, GenericDocument)
or onUpgrade(int, int, GenericDocument)
will be triggered if the version number of
the schema stored in AppSearch is different with the version in the request.
If any error or Exception occurred in the onDowngrade(int, int, GenericDocument)
or onUpgrade(int, int, GenericDocument)
, all the setSchema request will be rejected
unless the schema changes are backwards-compatible, and stored documents won't have any
observable changes.
Public Constructor Summary
Public Method Summary
| abstract GenericDocument | |
| abstract GenericDocument | |
| abstract boolean | shouldMigrate
(int currentVersion, int finalVersion)
Returns
true
if this migrator's source type needs to be migrated
to update from currentVersion to finalVersion. |
Inherited Method Summary
Public Constructors
public Migrator ()
Public Methods
public abstract GenericDocument onDowngrade (int currentVersion, int finalVersion, GenericDocument document)
Migrates GenericDocument
to an older version of AppSearchSchema
.
This method will be invoked only if the SetSchemaRequest
is setting a lower version number than the current AppSearchSchema
saved in AppSearch.
If this Migrator
is provided to cover a compatible schema change via AppSearchClient.setSchema(SetSchemaRequest, String)
, documents under the old
version won't be removed unless you use the same document ID.
This method will be invoked on the background worker thread.
Parameters
| currentVersion | The current version of the document's schema. |
|---|---|
| finalVersion | The final version that documents need to be migrated to. |
| document | The GenericDocument
need to be translated to new version. |
Returns
- A
GenericDocumentin new version.
public abstract GenericDocument onUpgrade (int currentVersion, int finalVersion, GenericDocument document)
Migrates GenericDocument
to a newer version of AppSearchSchema
.
This method will be invoked only if the SetSchemaRequest
is setting a higher version number than the current AppSearchSchema
saved in AppSearch.
If this Migrator
is provided to cover a compatible schema change via AppSearchClient.setSchema(SetSchemaRequest, String)
, documents under the old
version won't be removed unless you use the same document ID.
This method will be invoked on the background worker thread provided via AppSearchClient.setSchema(SetSchemaRequest, String)
.
Parameters
| currentVersion | The current version of the document's schema. |
|---|---|
| finalVersion | The final version that documents need to be migrated to. |
| document | The GenericDocument
need to be translated to new version. |
Returns
- A
GenericDocumentin new version.
public abstract boolean shouldMigrate (int currentVersion, int finalVersion)
Returns true
if this migrator's source type needs to be migrated to
update from currentVersion to finalVersion.
Migration won't be triggered if currentVersion is equal to finalVersion even if shouldMigrate(int, int)
return true;
