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When schema changes are additive, old clients would just ignore the new tables and columns, and no special handling is required. However, in some cases, the schema changes may be more drastic and may need separate Sync Streams (or Sync Rules) based on the client version.
To distinguish between client versions, clients can pass version information to the PowerSync Service. In Sync Streams, these are called connection parameters (accessed via connection.parameter()). In legacy Sync Rules, these are called client parameters.
Example to use different table names based on the client’s schema_version:
Sync Streams
Sync Rules (Legacy)
# Client passes connection params: {"schema_version": <version>}
streams:
assets_v1:
query: SELECT * FROM assets AS assets_v1
WHERE user_id = auth.user_id()
AND connection.parameter('schema_version') = '1'
assets_v2:
query: SELECT * FROM assets AS assets_v2
WHERE user_id = auth.user_id()
AND connection.parameter('schema_version') = '2'
# Client passes in: "params": {"schema_version": <version>}
assets_v1:
parameters: SELECT request.user_id() AS user_id
WHERE request.parameters() ->> 'schema_version' = '1'
data:
- SELECT * FROM assets AS assets_v1 WHERE user_id = bucket.user_id
assets_v2:
parameters: SELECT request.user_id() AS user_id
WHERE request.parameters() ->> 'schema_version' = '2'
data:
- SELECT * FROM assets AS assets_v2 WHERE user_id = bucket.user_id
Handle queries based on parameters set by the client with care. The client can send any value for these parameters, so it’s not a good place to do authorization. If the parameter must be authenticated, use parameters from the JWT instead.
