MetaApi supports multi tenant

[BohuTANG]

Summary

It seems MetaApi is a global view, can not get a tenant database/table:

databend/query/src/catalogs/backends/impls/meta_remote.rs

Lines 79 to 137 in dd7a004

	impl MetaApi for MetaRemote {
	async fn create_database(&self, req: CreateDatabaseReq) -> Result<CreateDatabaseReply> {
	self.query_backend(move |cli| async move { cli.create_database(req).await })
	.await
	}
	async fn drop_database(&self, req: DropDatabaseReq) -> Result<DropDatabaseReply> {
	self.query_backend(move |cli| async move { cli.drop_database(req).await })
	.await
	}
	async fn get_database(&self, req: GetDatabaseReq) -> Result<Arc<DatabaseInfo>> {
	self.query_backend(move |cli| async move { cli.get_database(req).await })
	.await
	}
	async fn list_databases(&self, req: ListDatabaseReq) -> Result<Vec<Arc<DatabaseInfo>>> {
	self.query_backend(move |cli| async move { cli.list_databases(req).await })
	.await
	}
	async fn create_table(&self, req: CreateTableReq) -> Result<CreateTableReply> {
	// TODO validate plan by table engine first
	self.query_backend(move |cli| async move { cli.create_table(req).await })
	.await
	}
	async fn drop_table(&self, req: DropTableReq) -> Result<DropTableReply> {
	self.query_backend(move |cli| async move { cli.drop_table(req).await })
	.await
	}
	async fn get_table(&self, req: GetTableReq) -> Result<Arc<TableInfo>> {
	self.query_backend(move |cli| async move { cli.get_table(req).await })
	.await
	}
	async fn list_tables(&self, req: ListTableReq) -> Result<Vec<Arc<TableInfo>>> {
	self.query_backend(move |cli| async move { cli.list_tables(req).await })
	.await
	}
	async fn get_table_by_id(&self, table_id: MetaId) -> Result<(TableIdent, Arc<TableMeta>)> {
	self.query_backend(move |cli| async move { cli.get_table_by_id(table_id).await })
	.await
	}
	async fn upsert_table_option(
	&self,
	req: UpsertTableOptionReq,
	) -> Result<UpsertTableOptionReply> {
	self.query_backend(move |cli| async move { cli.upsert_table_option(req).await })
	.await
	}
	fn name(&self) -> String {
	"meta-remote".to_owned()
	}
	}

The KVApi works well with a prefix.

[drmingdrmer]

With tenant id, the namespace for a table would be tenant_id/user_id/database/table or tenant_id/database/table?
I.e., is it legal that two user have database with the same database name?

[ariesdevil]

IMO yes, two tenants can have the same database name and a tenant can have multiple users.
Correct me if I was wrong.

[BohuTANG]

For databend use case, tenant_id/database/table is ok, there is no user_id from catelog.