Add ability to merge dataset buckets. Useful when using numerous different datasets.

jobs/process/BaseSDTrainProcess.py

@@ -2244,10 +2244,15 @@ class BaseSDTrainProcess(BaseTrainProcess):
                         ds.cache_tensors_to_disk = True
         # load datasets if passed in the root process
         if self.datasets is not None:
-            self.data_loader = get_dataloader_from_datasets(self.datasets, self.train_config.batch_size, self.sd)
+            self.data_loader = get_dataloader_from_datasets(
+                self.datasets, self.train_config.batch_size, self.sd,
+                pool_datasets=self.train_config.pool_datasets,
+            )
         if self.datasets_reg is not None:
-            self.data_loader_reg = get_dataloader_from_datasets(self.datasets_reg, self.train_config.batch_size,
-                                                                self.sd)
+            self.data_loader_reg = get_dataloader_from_datasets(
+                self.datasets_reg, self.train_config.batch_size, self.sd,
+                pool_datasets=self.train_config.pool_datasets,
+            )
 
         flush()
         self.last_save_step = self.step_num