Reduce memory footprint of Database.insert()

CHANGELOG.rst

@@ -7,6 +7,7 @@ Unreleased
 - Fix problem with SELECT WITH TOTALS (pilosus)
 - Update serialization format of DateTimeField to 10 digits, zero padded (nikepan)
 - Greatly improve performance when inserting large strings (credit to M1hacka for identifying the problem)
+- Reduce memory footprint of Database.insert()
 
 v0.8.0
 ------

src/infi/clickhouse_orm/database.py

@@ -50,6 +50,7 @@ class Database(object):
 
     def insert(self, model_instances, batch_size=1000):
         from six import next
+        from cStringIO import StringIO
         i = iter(model_instances)
         try:
             first_instance = next(i)
@@ -61,22 +62,27 @@ class Database(object):
             raise DatabaseException("You can't insert into read only table")
 
         def gen():
-            yield self._substitute('INSERT INTO $table FORMAT TabSeparated\n', model_class).encode('utf-8')
+            buf = StringIO()
+            buf.write(self._substitute('INSERT INTO $table FORMAT TabSeparated\n', model_class).encode('utf-8'))
             first_instance.set_database(self)
-            yield (first_instance.to_tsv(include_readonly=False) + '\n').encode('utf-8')
+            buf.write(first_instance.to_tsv(include_readonly=False).encode('utf-8'))
+            buf.write('\n')
             # Collect lines in batches of batch_size
-            batch = []
+            lines = 2
             for instance in i:
                 instance.set_database(self)
-                batch.append(instance.to_tsv(include_readonly=False))
-                if len(batch) >= batch_size:
+                buf.write(instance.to_tsv(include_readonly=False).encode('utf-8'))
+                buf.write('\n')
+                lines += 1
+                if lines >= batch_size:
                     # Return the current batch of lines
-                    yield ('\n'.join(batch) + '\n').encode('utf-8')
+                    yield buf.getvalue()
                     # Start a new batch
-                    batch = []
+                    buf = StringIO()
+                    lines = 0
             # Return any remaining lines in partial batch
-            if batch:
-                yield ('\n'.join(batch) + '\n').encode('utf-8')
+            if lines:
+                yield buf.getvalue()
         self._send(gen())
 
     def count(self, model_class, conditions=None):