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Matt Burgess commented on NIFI-4385: ------------------------------------ For large tables, GenerateTableFetch is the way to go. If you have a standalone NiFi instance and want to fetch a ton of rows, it's going to be slow. > Adjust the QueryDatabaseTable processor for handling big tables. > ---------------------------------------------------------------- > > Key: NIFI-4385 > URL: https://issues.apache.org/jira/browse/NIFI-4385 > Project: Apache NiFi > Issue Type: Improvement > Components: Core Framework > Affects Versions: 1.3.0 > Reporter: Tim Späth > Priority: Major > > When querying large database tables, the *QueryDatabaseTable* processor does > not perform very well. > The processor will always perform the full query and then transfer all > flowfiles as a list instead of > transferring them particularly after the *ResultSet* is fetching the next > rows(If a fetch size is given). > If you want to query a billion rows from a table, > the processor will add all flowfiles in an ArrayList<FlowFile> in memory > before transferring the whole list after the last row is fetched by the > ResultSet. > I've checked the code in > *org.apache.nifi.processors.standard.QueryDatabaseTable.java* > and in my opinion, it would be no big deal to move the session.transfer to a > proper position in the code (into the while loop where the flowfile is added > to the list) to > achieve a real _stream support_. There was also a bug report for this problem > which resulted in adding the new property *Maximum Number of Fragments*, > but this property will just limit the results. > Now you have to multiply *Max Rows Per Flow File* with *Maximum Number of > Fragments* to get your limit, > which is not really a solution for the original problem imho. > Also the workaround with GenerateTableFetch and/or ExecuteSQL processors is > much slower than using a database cursor or a ResultSet > and stream the rows in flowfiles directly in the queue. -- This message was sent by Atlassian Jira (v8.20.10#820010)