MongoCursor::batchSize
(PECL mongo >=1.0.11)
MongoCursor::batchSize — Limits the number of elements returned in one batch
Description
A cursor typically fetches a batch of result objects and store them locally. This method sets the batchSize value to configure the amount of documents retrieved from the server in one round trip. However, it will never return more documents than fit in the max batch size limit (usually 4MB).
Parameters
-
batchSize -
The number of results to return per batch. Each batch requires a round-trip to the server.
If
batchSizeis 2 or more, it represents the size of each batch of objects retrieved. It can be adjusted to optimize performance and limit data transfer.If
batchSizeis 1 or negative, it will limit of number returned documents to the absolute value of batchSize, and the cursor will be closed. For example if batchSize is -10, then the server will return a maximum of 10 documents and as many as can fit in 4MB, then close the cursor.WarningA
batchSizeof 1 is special, and means the same as -1, i.e. a value of 1 makes the cursor only capable of returning one document.Note that this feature is different from MongoCursor::limit() in that documents must fit within a maximum size, and it removes the need to send a request to close the cursor server-side. The batch size can be changed even after a cursor is iterated, in which case the setting will apply on the next batch retrieval.
This cannot override MongoDB's limit on the amount of data it will return to the client (i.e., if you set batch size to 1,000,000,000, MongoDB will still only return 4-16MB of results per batch).
To ensure consistent behavior, the rules of MongoCursor::batchSize() and MongoCursor::limit() behave a little complex but work "as expected". The rules are: hard limits override soft limits with preference given to MongoCursor::limit() over MongoCursor::batchSize(). After that, whichever is set and lower than the other will take precedence. See below. section for some examples.
Examples
Example #1 MongoCursor::batchSize() and combinations with MongoCursor::limit()
<?php
// one batch, at most 10 items. The -10 makes the server to return 10 items,
// and then remove the cursor.
$cursor->limit(20)->batchSize(-10);
// first batch: at most 10 items
$cursor->limit(10);
// first batch: at most 10 items
$cursor->limit(10)->batchSize(20);
// results are fetched in batches of 10 each, with a maximum of 20 items
// returned (that means two batches of 10).
$cursor->limit(20)->batchSize(10);
// results are fetched in batches of 7 each, with a maximum of 30 items
// returned (that means that the driver requests 4 batches of 7, and one batch
// of 2).
$cursor->limit(30)->batchSize(7)
?>
See Also
MongoDB core docs on » batchSize.
- MongoCursor::limit() - Limits the number of results returned
- MongoCursorInterface::batchSize() - Limits the number of elements returned in one batch
Changelog
| Version | Description |
|---|---|
| 1.4.5 |
Before 1.4.5, this method would throw an MongoCursorException if the cursor had already started iterating. |
English translation
You have asked to visit this site in English. For now, only the interface is translated, but not all the content yet.If you want to help me in translations, your contribution is welcome. All you need to do is register on the site, and send me a message asking me to add you to the group of translators, which will give you the opportunity to translate the pages you want. A link at the bottom of each translated page indicates that you are the translator, and has a link to your profile.
Thank you in advance.
Document created the 30/01/2003, last modified the 26/10/2018
Source of the printed document:https://www.gaudry.be/en/php-rf-mongocursor.batchsize.html
The infobrol is a personal site whose content is my sole responsibility. The text is available under CreativeCommons license (BY-NC-SA). More info on the terms of use and the author.
References
These references and links indicate documents consulted during the writing of this page, or which may provide additional information, but the authors of these sources can not be held responsible for the content of this page.
The author This site is solely responsible for the way in which the various concepts, and the freedoms that are taken with the reference works, are presented here. Remember that you must cross multiple source information to reduce the risk of errors.
