Apache NIFI "Execute Processor"

Question

Can Apache NIFI "ExecuteSQL Processor" stream large set of select result in chunks say 'x' MB?

Answer 1

The ExecuteSQL Processor can "stream" large numbers of rows in the sense that it will stream the data directly to FlowFile content (which will not be held in-memory/heap) so it is very memory efficient. It does not, at this time, chunk the results, though. There is a ticket https://issues.apache.org/jira/browse/NIFI-1251 to provide such capabilities, though.

Answer 2

现在，您可以使用通过“每个流文件的最大行数”属性支持分块的QueryDatabaseTable处理器。

Answer 3

You can also specify a limit statement in the SQL itself (along with a sort by ID), pull one batch, get the last ID, pull all >max(id), repeat until done, ie

                                       Start
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    UpdateAttr: maxid--------- SQL ... $maxid:isEmpty():ifElse('', 'where id>maxid') order by id limit n
           |_____________________________|
                                         |
                                        do sth

it's by # records and not size - but knowing the approx size per record, you can still do it