blocks|key|728912|text|我对此不是百分之百确定，但我过去所做的是将最后一个光标与实际光标进行比较，我想我注意到它们是相同的，所以我得出结论，它是最后一个光标。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|728913|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

i am not 100% sure about that but what i used to do is compare the last cursor with the actual cursor and i think i noticed that they were the same so i came to the conclusion that it was the last cursor.

blocks|key|993656|text|如果计算查询结果的数量，并且该数量等于fetch，则需要获取更多的结果。如果结果数少于您已获取的所有查询结果。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|993657|为了演示这个想法:我使用这个函数在App+Engine和Google+Apps电子表格之间传输数据。传输是以页面为单位进行的；此函数尝试优化页面大小。参数“cursor”保持光标不动。第一次参数‘’cursor‘=+None。args'+page‘保存页面大小。查询可以是这样的:+query+=+aLotofData.all()|993658|def+makePage(args,+proces,+query):

++++if+args['Cursor']+!=+'NONE'+:+query.with_cursor(args['Cursor'])++#+next+page+with+cursor

++++page+=+[]+++++++++++++++++++++++++++++++++++++++++++++++++++#+transfer+the+selected+entities+in+pages
++++lines+=+0+++++++++++++++++++++++++++++++++++++++++++++++++++#+lines+per+page+counter
++++fetch+=+int(args['Page'])+++++++++++++++++++++++++++++++++++#+fetch+can+vary;+because+we+optimize+the+page+transfer+
++++while+lines+<+0.8+*+int(args['Page'])+:+++++++++++++++++++++#+optimize+pagination+when+page+less+than+80%25+filled
++++++++count+=+0+++++++++++++++++++++++++++++++++++++++++++++++#+number+of+entities+processed+per+fetch
++++++++for+entity+in+query.fetch(fetch)+:
++++++++++++count+%2B=+1
++++++++++++page_line+=+proces(entity)
++++++++++++if+page_line+:+++++++++++
++++++++++++++++page.append(page_line)++++++++++++++++++++++++++#+variable+function+call+to+preces+the+entity
++++++++++++++++lines+%2B=+1
++++++++if+count+<+fetch+:++++++++++++++++++++++++++++++++++++++#+no+more+entities+?
++++++++++++cursor+=+'NONE'+++++++++++++++++++++++++++++++++++++#+last+page,+no+cursor+
++++++++++++break
++++++++cursor+=+query.cursor()+++++++++++++++++++++++++++++++++#+save+current+cursor+fot+he+next+run++++++++++++++++
++++++++query.with_cursor(cursor)+++++++++++++++++++++++++++++++#+set+the+cursor+for+the+fetch+iteration+(optimize)
++++++++fetch+=+int(args['Page'])+-+lines+++++++++++++++++++++++#+and+fetch+the+number+of+page+lines+left+to+fill

++++logging.debug('Transfered+:+%25d+next_cursor+:+%25s'+%25(lines,+cursor))+

++++return+simplejson.dumps({'cursor'+:+cursor,+'page'+:+page})|code-block|syntax|javascript|993659|函数"proces“处理每个实体。当proces返回None时，该行不会附加到当前页。|993660|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you count your query results and the number is equal to the fetch, you have more results to fetch. If the number of results is less, than you have fetched all query results.

To demonstrate the idea : I use this function to transfer data between App Engine and a Google Apps spreadsheet. The transfer is done in pages; This function tries yo optimize the page size. 
args['Cursor'] hold the cursor. The first time args['cursor'] = None. args['Page'] holds the page size.
The query can be something like : query = aLotofData.all()

<pre><code>def makePage(args, proces, query):

 if args['Cursor'] != 'NONE' : query.with_cursor(args['Cursor']) # next page with cursor

 page = [] # transfer the selected entities in pages
 lines = 0 # lines per page counter
 fetch = int(args['Page']) # fetch can vary; because we optimize the page transfer 
 while lines &lt; 0.8 * int(args['Page']) : # optimize pagination when page less than 80% filled
 count = 0 # number of entities processed per fetch
 for entity in query.fetch(fetch) :
 count += 1
 page_line = proces(entity)
 if page_line : 
 page.append(page_line) # variable function call to preces the entity
 lines += 1
 if count &lt; fetch : # no more entities ?
 cursor = 'NONE' # last page, no cursor 
 break
 cursor = query.cursor() # save current cursor fot he next run 
 query.with_cursor(cursor) # set the cursor for the fetch iteration (optimize)
 fetch = int(args['Page']) - lines # and fetch the number of page lines left to fill

 logging.debug('Transfered : %d next_cursor : %s' %(lines, cursor)) 

 return simplejson.dumps({'cursor' : cursor, 'page' : page})
</code></pre>

The function "proces" processes each entity. When proces returns None, the line is not appended to the current page.

blocks|key|5031740|text|如果您的模型正在扩展ndb，则应该使用fetch_page()。如果它没有扩展ndb，您可能需要考虑更改。它不是完全向后兼容的，但数据不需要迁移。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5031741|from+google.appengine.ext.ndb+import+model

class+User(model.Model):
+++name+=+model.StringProperty()

users,+cursor,+more+=+User.query(User.name+==+"Jon").fetch_page(25)

if+more:+
++++#+Do+next+page+logic
++++next_users+=+User.query(User.name+==+"Jon").fetch_page(25,+start_cursor=cursor)|code-block|syntax|javascript|5031742|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If your model is extending ndb, you should use fetch_page(). If it's not extending ndb, you may want to consider changing. It's not completely backwards compatible but the data does not have to be migrated.

<pre><code>from google.appengine.ext.ndb import model

class User(model.Model):
 name = model.StringProperty()

users, cursor, more = User.query(User.name == "Jon").fetch_page(25)

if more: 
 # Do next page logic
 next_users = User.query(User.name == "Jon").fetch_page(25, start_cursor=cursor)
</code></pre>

I am fetching records from gae model using cursor() and with_cursor() logic as used in paging. but i am not sure how to check that there is no any other record in db that is pointed by cursor. i am fetching these records in chunks within some iterations.when i got my required results in the first iteration then in next iteration I want to check there is no any record in model but I not get any empty/None value of cursor at this stage.please let me know how to perform this check with cursors in google app engine with python.

cursor and with_cursor() in GAE

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我使用cursor()和with_cursor()逻辑从gae模型中获取记录，就像分页中使用的那样。但是我不确定如何检查db中是否有任何其他记录是由游标指向的。我在一些iterations.when中获取这些记录的块，我在第一次迭代中得到了我需要的结果，然后在下一次迭代中，我想检查模型中没有任何记录，但我在这个stag...

问GAE中的游标和with_cursor()
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