Hi Qing, > Does it guarantee that it will be called in the same order of elements in the stream, where value2 is always 1 element after value1?
Order is maintained within each parallel stream partition. If the reduce operator only has one sending- sub-task, the answer is YES, but if reduce operator has multiple sending- sub-task, order among elements is only preserved for each pair of sending- and receiving tasks. The answers under https://stackoverflow.com/questions/38354713/ordering-of-records-in-stream might help. Best, Yanfei Qing Lim <q....@mwam.com> 于2022年11月3日周四 01:32写道： > Hi, Flink User Group > > > > I am trying to use Reduce function, I wonder does it guarantee order when > its called? > > > > The signature is as follow: > > > > T reduce(T value1, T value2) throws Exception; > > > > Does it guarantee that it will be called in the same order of elements in > the stream, where value2 is always 1 element after value1? > > > > Kind regards > > > > > > *Qing Lim *| Marshall Wace LLP, George House, 131 Sloane Street, London | > E-mail: > q....@mwam.com | Tel: +44 207 925 4865 > > > > > > This e-mail and any attachments are confidential to the addressee(s) and > may contain information that is legally privileged and/or confidential. If > you are not the intended recipient of this e-mail you are hereby notified > that any dissemination, distribution, or copying of its content is strictly > prohibited. If you have received this message in error, please notify the > sender by return e-mail and destroy the message and all copies in your > possession. > > > To find out more details about how we may collect, use and share your > personal information, please see https://www.mwam.com/privacy-policy. > This includes details of how calls you make to us may be recorded in order > for us to comply with our legal and regulatory obligations. > > > To the extent that the contents of this email constitutes a financial > promotion, please note that it is issued only to and/or directed only at > persons who are professional clients or eligible counterparties as defined > in the FCA Rules. Any investment products or services described in this > email are available only to professional clients and eligible > counterparties. Persons who are not professional clients or eligible > counterparties should not rely or act on the contents of this email. > > > Marshall Wace LLP is authorised and regulated by the Financial Conduct > Authority. Marshall Wace LLP is a limited liability partnership registered > in England and Wales with registered number OC302228 and registered office > at George House, 131 Sloane Street, London, SW1X 9AT. If you are receiving > this e-mail as a client, or an investor in an investment vehicle, managed > or advised by Marshall Wace North America L.P., the sender of this e-mail > is communicating with you in the sender's capacity as an associated or > related person of Marshall Wace North America L.P. ("MWNA"), which is > registered with the US Securities and Exchange Commission ("SEC") as an > investment adviser. Registration with the SEC does not imply that MWNA or > its employees possess a certain level of skill or training. >
