From 70874a2501c91304731b6393b6f7318008954079 Mon Sep 17 00:00:00 2001
From: Abdurrahmaan Iqbal <abdurrahmaaniqbal@hotmail.com>
Date: Mon, 8 Jul 2019 17:48:05 +0100
Subject: [PATCH] Implement update_many and upsert_many

---
 dataset/table.py | 75 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 74 insertions(+), 1 deletion(-)

diff --git a/dataset/table.py b/dataset/table.py
index bf829df..668e9be 100644
--- a/dataset/table.py
+++ b/dataset/table.py
@@ -3,7 +3,7 @@ import warnings
 import threading
 
 from sqlalchemy.sql import and_, expression
-from sqlalchemy.sql.expression import ClauseElement
+from sqlalchemy.sql.expression import bindparam, ClauseElement
 from sqlalchemy.schema import Column, Index
 from sqlalchemy import func, select, false
 from sqlalchemy.schema import Table as SQLATable
@@ -163,6 +163,51 @@ class Table(object):
         if return_count:
             return self.count(clause)
 
+    def update_many(self, rows, keys, chunk_size=1000, ensure=None, types=None):
+        """Update many rows in the table at a time.
+
+        This is significantly faster than updating them one by one. Per default
+        the rows are processed in chunks of 1000 per commit, unless you specify
+        a different ``chunk_size``.
+
+        See :py:meth:`update() <dataset.Table.update>` for details on
+        the other parameters.
+        """
+        chunk = []
+        columns = set()
+        for row in rows:
+            chunk.append(row)
+            columns = columns.union(set(row.keys()))
+
+            # bindparam requires names to not conflict (cannot be "id" for id)
+            for key in keys:
+                row[f'_{key}'] = row[f'{key}']
+
+            if len(chunk) == chunk_size:
+                stmt = self.table.update(
+                    whereclause=and_(
+                        *[self.table.c[key] == bindparam(f'_{key}') for key in keys]
+                    ),
+                    values={
+                        column: bindparam(column, required=False) for column in columns
+                    }
+                )
+                self.db.executable.execute(stmt, chunk)
+                chunk = []
+                columns = set()
+
+        if len(chunk):
+            stmt = self.table.update(
+                whereclause=and_(
+                    *[self.table.c[key] == bindparam(f'_{key}') for key in keys]
+                ),
+                values={
+                    column: bindparam(column, required=False) for column in columns
+                }
+            )
+            self.db.executable.execute(stmt, chunk)
+
+
     def upsert(self, row, keys, ensure=None, types=None):
         """An UPSERT is a smart combination of insert and update.
 
@@ -181,6 +226,34 @@ class Table(object):
             return self.insert(row, ensure=False)
         return True
 
+    def upsert_many(self, rows, keys, chunk_size=1000, ensure=None, types=None):
+        """
+        Sorts multiple input rows into upserts and inserts. Inserts are passed
+        to insert_many and upserts are updated.
+
+        See :py:meth:`upsert() <dataset.Table.upsert>` and
+        :py:meth:`insert_many() <dataset.Table.insert_many>`.
+        """
+        # Convert keys to a list if not a list or tuple.
+        keys = keys if type(keys) in (list, tuple) else [keys]
+
+        to_insert = []
+        to_update = []
+        for row in rows:
+            if self.find_one(**{key: row.get(key) for key in keys}):
+                # Row exists - update it.
+                to_update.append(row)
+            else:
+                # Row doesn't exist - insert it.
+                to_insert.append(row)
+
+        # Insert non-existing rows.
+        self.insert_many(to_insert, chunk_size, ensure, types)
+
+        # Update existing rows.
+        self.update_many(to_update, keys, chunk_size, ensure, types)
+
+
     def delete(self, *clauses, **filters):
         """Delete rows from the table.